4. Proxies ---------- Proxy configuration can be located in a set of sections : - defaults <name> - frontend <name> - backend <name> - listen <name> A "defaults" section sets default parameters for all other sections following its declaration. Those default parameters are reset by the next "defaults" section. See below for the list of parameters which can be set in a "defaults" section. The name is optional but its use is encouraged for better readability. A "frontend" section describes a set of listening sockets accepting client connections. A "backend" section describes a set of servers to which the proxy will connect to forward incoming connections. A "listen" section defines a complete proxy with its frontend and backend parts combined in one section. It is generally useful for TCP-only traffic. All proxy names must be formed from upper and lower case letters, digits, '-' (dash), '_' (underscore) , '.' (dot) and ':' (colon). ACL names are case-sensitive, which means that "www" and "WWW" are two different proxies. Historically, all proxy names could overlap, it just caused troubles in the logs. Since the introduction of content switching, it is mandatory that two proxies with overlapping capabilities (frontend/backend) have different names. However, it is still permitted that a frontend and a backend share the same name, as this configuration seems to be commonly encountered. Right now, two major proxy modes are supported : "tcp", also known as layer 4, and "http", also known as layer 7. In layer 4 mode, HAProxy simply forwards bidirectional traffic between two sides. In layer 7 mode, HAProxy analyzes the protocol, and can interact with it by allowing, blocking, switching, adding, modifying, or removing arbitrary contents in requests or responses, based on arbitrary criteria. In HTTP mode, the processing applied to requests and responses flowing over a connection depends in the combination of the frontend's HTTP options and the backend's. HAProxy supports 5 connection modes : - KAL : keep alive ("option http-keep-alive") which is the default mode : all requests and responses are processed, and connections remain open but idle between responses and new requests. - TUN: tunnel ("option http-tunnel") : this was the default mode for versions 1.0 to 1.5-dev21 : only the first request and response are processed, and everything else is forwarded with no analysis at all. This mode should not be used as it creates lots of trouble with logging and HTTP processing. - PCL: passive close ("option httpclose") : exactly the same as tunnel mode, but with "Connection: close" appended in both directions to try to make both ends close after the first request/response exchange. - SCL: server close ("option http-server-close") : the server-facing connection is closed after the end of the response is received, but the client-facing connection remains open. - FCL: forced close ("option forceclose") : the connection is actively closed after the end of the response. The effective mode that will be applied to a connection passing through a frontend and a backend can be determined by both proxy modes according to the following matrix, but in short, the modes are symmetric, keep-alive is the weakest option and force close is the strongest. Backend mode | KAL | TUN | PCL | SCL | FCL ----+-----+-----+-----+-----+---- KAL | KAL | TUN | PCL | SCL | FCL ----+-----+-----+-----+-----+---- TUN | TUN | TUN | PCL | SCL | FCL Frontend ----+-----+-----+-----+-----+---- mode PCL | PCL | PCL | PCL | FCL | FCL ----+-----+-----+-----+-----+---- SCL | SCL | SCL | FCL | SCL | FCL ----+-----+-----+-----+-----+---- FCL | FCL | FCL | FCL | FCL | FCL 4.1. Proxy keywords matrix -------------------------- The following list of keywords is supported. Most of them may only be used in a limited set of section types. Some of them are marked as "deprecated" because they are inherited from an old syntax which may be confusing or functionally limited, and there are new recommended keywords to replace them. Keywords marked with "(*)" can be optionally inverted using the "no" prefix, eg. "no option contstats". This makes sense when the option has been enabled by default and must be disabled for a specific instance. Such options may also be prefixed with "default" in order to restore default settings regardless of what has been specified in a previous "defaults" section. keyword defaults frontend listen backend ------------------------------------+----------+----------+---------+--------- acl - X X X appsession - - X X backlog X X X - balance X - X X bind - X X - bind-process X X X X block - X X X capture cookie - X X - capture request header - X X - capture response header - X X - clitimeout (deprecated) X X X - compression X X X X contimeout (deprecated) X - X X cookie X - X X default-server X - X X default_backend X X X - description - X X X disabled X X X X dispatch - - X X enabled X X X X errorfile X X X X errorloc X X X X errorloc302 X X X X -- keyword -------------------------- defaults - frontend - listen -- backend - errorloc303 X X X X force-persist - X X X fullconn X - X X grace X X X X hash-type X - X X http-check disable-on-404 X - X X http-check expect - - X X http-check send-state X - X X http-request - X X X http-response - X X X http-send-name-header - - X X id - X X X ignore-persist - X X X log (*) X X X X log-format X X X - max-keep-alive-queue X - X X maxconn X X X - mode X X X X monitor fail - X X - monitor-net X X X - monitor-uri X X X - option abortonclose (*) X - X X option accept-invalid-http-request (*) X X X - option accept-invalid-http-response (*) X - X X option allbackups (*) X - X X option checkcache (*) X - X X option clitcpka (*) X X X - option contstats (*) X X X - option dontlog-normal (*) X X X - option dontlognull (*) X X X - option forceclose (*) X X X X -- keyword -------------------------- defaults - frontend - listen -- backend - option forwardfor X X X X option http-ignore-probes (*) X X X - option http-keep-alive (*) X X X X option http-no-delay (*) X X X X option http-pretend-keepalive (*) X X X X option http-server-close (*) X X X X option http-tunnel (*) X X X X option http-use-proxy-header (*) X X X - option httpchk X - X X option httpclose (*) X X X X option httplog X X X X option http_proxy (*) X X X X option independent-streams (*) X X X X option ldap-check X - X X option log-health-checks (*) X - X X option log-separate-errors (*) X X X - option logasap (*) X X X - option mysql-check X - X X option pgsql-check X - X X option nolinger (*) X X X X option originalto X X X X option persist (*) X - X X option redispatch (*) X - X X option redis-check X - X X option smtpchk X - X X option socket-stats (*) X X X - option splice-auto (*) X X X X option splice-request (*) X X X X option splice-response (*) X X X X option srvtcpka (*) X - X X option ssl-hello-chk X - X X -- keyword -------------------------- defaults - frontend - listen -- backend - option tcp-check X - X X option tcp-smart-accept (*) X X X - option tcp-smart-connect (*) X - X X option tcpka X X X X option tcplog X X X X option transparent (*) X - X X persist rdp-cookie X - X X rate-limit sessions X X X - redirect - X X X redisp (deprecated) X - X X redispatch (deprecated) X - X X reqadd - X X X reqallow - X X X reqdel - X X X reqdeny - X X X reqiallow - X X X reqidel - X X X reqideny - X X X reqipass - X X X reqirep - X X X reqisetbe - X X X reqitarpit - X X X reqpass - X X X reqrep - X X X -- keyword -------------------------- defaults - frontend - listen -- backend - reqsetbe - X X X reqtarpit - X X X retries X - X X rspadd - X X X rspdel - X X X rspdeny - X X X rspidel - X X X rspideny - X X X rspirep - X X X rsprep - X X X server - - X X source X - X X srvtimeout (deprecated) X - X X stats admin - - X X stats auth X - X X stats enable X - X X stats hide-version X - X X stats http-request - - X X stats realm X - X X stats refresh X - X X stats scope X - X X stats show-desc X - X X stats show-legends X - X X stats show-node X - X X stats uri X - X X -- keyword -------------------------- defaults - frontend - listen -- backend - stick match - - X X stick on - - X X stick store-request - - X X stick store-response - - X X stick-table - - X X tcp-check connect - - X X tcp-check expect - - X X tcp-check send - - X X tcp-check send-binary - - X X tcp-request connection - X X - tcp-request content - X X X tcp-request inspect-delay - X X X tcp-response content - - X X tcp-response inspect-delay - - X X timeout check X - X X timeout client X X X - timeout client-fin X X X - timeout clitimeout (deprecated) X X X - timeout connect X - X X timeout contimeout (deprecated) X - X X timeout http-keep-alive X X X X timeout http-request X X X X timeout queue X - X X timeout server X - X X timeout server-fin X - X X timeout srvtimeout (deprecated) X - X X timeout tarpit X X X X timeout tunnel X - X X transparent (deprecated) X - X X unique-id-format X X X - unique-id-header X X X - use_backend - X X - use-server - - X X ------------------------------------+----------+----------+---------+--------- keyword defaults frontend listen backend 4.2. Alphabetically sorted keywords reference --------------------------------------------- This section provides a description of each keyword and its usage. acl <aclname> <criterion> [flags] [operator] <value> ... Declare or complete an access list. May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Example: acl invalid_src src 0.0.0.0/7 224.0.0.0/3 acl invalid_src src_port 0:1023 acl local_dst hdr(host) -i localhost See section 7 about ACL usage. appsession <cookie> len <length> timeout <holdtime> [request-learn] [prefix] [mode <path-parameters|query-string>] Define session stickiness on an existing application cookie. May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <cookie> this is the name of the cookie used by the application and which HAProxy will have to learn for each new session. <length> this is the max number of characters that will be memorized and checked in each cookie value. <holdtime> this is the time after which the cookie will be removed from memory if unused. If no unit is specified, this time is in milliseconds. request-learn If this option is specified, then haproxy will be able to learn the cookie found in the request in case the server does not specify any in response. This is typically what happens with PHPSESSID cookies, or when haproxy's session expires before the application's session and the correct server is selected. It is recommended to specify this option to improve reliability. prefix When this option is specified, haproxy will match on the cookie prefix (or URL parameter prefix). The appsession value is the data following this prefix. Example : appsession ASPSESSIONID len 64 timeout 3h prefix This will match the cookie ASPSESSIONIDXXXX=XXXXX, the appsession value will be XXXX=XXXXX. mode This option allows to change the URL parser mode. 2 modes are currently supported : - path-parameters : The parser looks for the appsession in the path parameters part (each parameter is separated by a semi-colon), which is convenient for JSESSIONID for example. This is the default mode if the option is not set. - query-string : In this mode, the parser will look for the appsession in the query string. When an application cookie is defined in a backend, HAProxy will check when the server sets such a cookie, and will store its value in a table, and associate it with the server's identifier. Up to <length> characters from the value will be retained. On each connection, haproxy will look for this cookie both in the "Cookie:" headers, and as a URL parameter (depending on the mode used). If a known value is found, the client will be directed to the server associated with this value. Otherwise, the load balancing algorithm is applied. Cookies are automatically removed from memory when they have been unused for a duration longer than <holdtime>. The definition of an application cookie is limited to one per backend. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours. Example : appsession JSESSIONID len 52 timeout 3h See also : "cookie", "capture cookie", "balance", "stick", "stick-table", "ignore-persist", "nbproc" and "bind-process". backlog <conns> Give hints to the system about the approximate listen backlog desired size May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <conns> is the number of pending connections. Depending on the operating system, it may represent the number of already acknowledged connections, of non-acknowledged ones, or both. In order to protect against SYN flood attacks, one solution is to increase the system's SYN backlog size. Depending on the system, sometimes it is just tunable via a system parameter, sometimes it is not adjustable at all, and sometimes the system relies on hints given by the application at the time of the listen() syscall. By default, HAProxy passes the frontend's maxconn value to the listen() syscall. On systems which can make use of this value, it can sometimes be useful to be able to specify a different value, hence this backlog parameter. On Linux 2.4, the parameter is ignored by the system. On Linux 2.6, it is used as a hint and the system accepts up to the smallest greater power of two, and never more than some limits (usually 32768). See also : "maxconn" and the target operating system's tuning guide. balance <algorithm> [ <arguments> ] balance url_param <param> [check_post] Define the load balancing algorithm to be used in a backend. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <algorithm> is the algorithm used to select a server when doing load balancing. This only applies when no persistence information is available, or when a connection is redispatched to another server. <algorithm> may be one of the following : roundrobin Each server is used in turns, according to their weights. This is the smoothest and fairest algorithm when the server's processing time remains equally distributed. This algorithm is dynamic, which means that server weights may be adjusted on the fly for slow starts for instance. It is limited by design to 4095 active servers per backend. Note that in some large farms, when a server becomes up after having been down for a very short time, it may sometimes take a few hundreds requests for it to be re-integrated into the farm and start receiving traffic. This is normal, though very rare. It is indicated here in case you would have the chance to observe it, so that you don't worry. static-rr Each server is used in turns, according to their weights. This algorithm is as similar to roundrobin except that it is static, which means that changing a server's weight on the fly will have no effect. On the other hand, it has no design limitation on the number of servers, and when a server goes up, it is always immediately reintroduced into the farm, once the full map is recomputed. It also uses slightly less CPU to run (around -1%). leastconn The server with the lowest number of connections receives the connection. Round-robin is performed within groups of servers of the same load to ensure that all servers will be used. Use of this algorithm is recommended where very long sessions are expected, such as LDAP, SQL, TSE, etc... but is not very well suited for protocols using short sessions such as HTTP. This algorithm is dynamic, which means that server weights may be adjusted on the fly for slow starts for instance. first The first server with available connection slots receives the connection. The servers are chosen from the lowest numeric identifier to the highest (see server parameter "id"), which defaults to the server's position in the farm. Once a server reaches its maxconn value, the next server is used. It does not make sense to use this algorithm without setting maxconn. The purpose of this algorithm is to always use the smallest number of servers so that extra servers can be powered off during non-intensive hours. This algorithm ignores the server weight, and brings more benefit to long session such as RDP or IMAP than HTTP, though it can be useful there too. In order to use this algorithm efficiently, it is recommended that a cloud controller regularly checks server usage to turn them off when unused, and regularly checks backend queue to turn new servers on when the queue inflates. Alternatively, using "http-check send-state" may inform servers on the load. source The source IP address is hashed and divided by the total weight of the running servers to designate which server will receive the request. This ensures that the same client IP address will always reach the same server as long as no server goes down or up. If the hash result changes due to the number of running servers changing, many clients will be directed to a different server. This algorithm is generally used in TCP mode where no cookie may be inserted. It may also be used on the Internet to provide a best-effort stickiness to clients which refuse session cookies. This algorithm is static by default, which means that changing a server's weight on the fly will have no effect, but this can be changed using "hash-type". uri This algorithm hashes either the left part of the URI (before the question mark) or the whole URI (if the "whole" parameter is present) and divides the hash value by the total weight of the running servers. The result designates which server will receive the request. This ensures that the same URI will always be directed to the same server as long as no server goes up or down. This is used with proxy caches and anti-virus proxies in order to maximize the cache hit rate. Note that this algorithm may only be used in an HTTP backend. This algorithm is static by default, which means that changing a server's weight on the fly will have no effect, but this can be changed using "hash-type". This algorithm supports two optional parameters "len" and "depth", both followed by a positive integer number. These options may be helpful when it is needed to balance servers based on the beginning of the URI only. The "len" parameter indicates that the algorithm should only consider that many characters at the beginning of the URI to compute the hash. Note that having "len" set to 1 rarely makes sense since most URIs start with a leading "/". The "depth" parameter indicates the maximum directory depth to be used to compute the hash. One level is counted for each slash in the request. If both parameters are specified, the evaluation stops when either is reached. url_param The URL parameter specified in argument will be looked up in the query string of each HTTP GET request. If the modifier "check_post" is used, then an HTTP POST request entity will be searched for the parameter argument, when it is not found in a query string after a question mark ('?') in the URL. The message body will only start to be analyzed once either the advertised amount of data has been received or the request buffer is full. In the unlikely event that chunked encoding is used, only the first chunk is scanned. Parameter values separated by a chunk boundary, may be randomly balanced if at all. This keyword used to support an optional <max_wait> parameter which is now ignored. If the parameter is found followed by an equal sign ('=') and a value, then the value is hashed and divided by the total weight of the running servers. The result designates which server will receive the request. This is used to track user identifiers in requests and ensure that a same user ID will always be sent to the same server as long as no server goes up or down. If no value is found or if the parameter is not found, then a round robin algorithm is applied. Note that this algorithm may only be used in an HTTP backend. This algorithm is static by default, which means that changing a server's weight on the fly will have no effect, but this can be changed using "hash-type". hdr(<name>) The HTTP header <name> will be looked up in each HTTP request. Just as with the equivalent ACL 'hdr()' function, the header name in parenthesis is not case sensitive. If the header is absent or if it does not contain any value, the roundrobin algorithm is applied instead. An optional 'use_domain_only' parameter is available, for reducing the hash algorithm to the main domain part with some specific headers such as 'Host'. For instance, in the Host value "haproxy.1wt.eu", only "1wt" will be considered. This algorithm is static by default, which means that changing a server's weight on the fly will have no effect, but this can be changed using "hash-type". rdp-cookie rdp-cookie(<name>) The RDP cookie <name> (or "mstshash" if omitted) will be looked up and hashed for each incoming TCP request. Just as with the equivalent ACL 'req_rdp_cookie()' function, the name is not case-sensitive. This mechanism is useful as a degraded persistence mode, as it makes it possible to always send the same user (or the same session ID) to the same server. If the cookie is not found, the normal roundrobin algorithm is used instead. Note that for this to work, the frontend must ensure that an RDP cookie is already present in the request buffer. For this you must use 'tcp-request content accept' rule combined with a 'req_rdp_cookie_cnt' ACL. This algorithm is static by default, which means that changing a server's weight on the fly will have no effect, but this can be changed using "hash-type". See also the rdp_cookie pattern fetch function. <arguments> is an optional list of arguments which may be needed by some algorithms. Right now, only "url_param" and "uri" support an optional argument. The load balancing algorithm of a backend is set to roundrobin when no other algorithm, mode nor option have been set. The algorithm may only be set once for each backend. Examples : balance roundrobin balance url_param userid balance url_param session_id check_post 64 balance hdr(User-Agent) balance hdr(host) balance hdr(Host) use_domain_only Note: the following caveats and limitations on using the "check_post" extension with "url_param" must be considered : - all POST requests are eligible for consideration, because there is no way to determine if the parameters will be found in the body or entity which may contain binary data. Therefore another method may be required to restrict consideration of POST requests that have no URL parameters in the body. (see acl reqideny http_end) - using a <max_wait> value larger than the request buffer size does not make sense and is useless. The buffer size is set at build time, and defaults to 16 kB. - Content-Encoding is not supported, the parameter search will probably fail; and load balancing will fall back to Round Robin. - Expect: 100-continue is not supported, load balancing will fall back to Round Robin. - Transfer-Encoding (RFC2616 3.6.1) is only supported in the first chunk. If the entire parameter value is not present in the first chunk, the selection of server is undefined (actually, defined by how little actually appeared in the first chunk). - This feature does not support generation of a 100, 411 or 501 response. - In some cases, requesting "check_post" MAY attempt to scan the entire contents of a message body. Scanning normally terminates when linear white space or control characters are found, indicating the end of what might be a URL parameter list. This is probably not a concern with SGML type message bodies. See also : "dispatch", "cookie", "appsession", "transparent", "hash-type" and "http_proxy". bind [<address>]:<port_range> [, ...] [param*] bind /<path> [, ...] [param*] Define one or several listening addresses and/or ports in a frontend. May be used in sections : defaults | frontend | listen | backend no | yes | yes | no Arguments : <address> is optional and can be a host name, an IPv4 address, an IPv6 address, or '*'. It designates the address the frontend will listen on. If unset, all IPv4 addresses of the system will be listened on. The same will apply for '*' or the system's special address "0.0.0.0". The IPv6 equivalent is '::'. Optionally, an address family prefix may be used before the address to force the family regardless of the address format, which can be useful to specify a path to a unix socket with no slash ('/'). Currently supported prefixes are : - 'ipv4@' -> address is always IPv4 - 'ipv6@' -> address is always IPv6 - 'unix@' -> address is a path to a local unix socket - 'abns@' -> address is in abstract namespace (Linux only). Note: since abstract sockets are not "rebindable", they do not cope well with multi-process mode during soft-restart, so it is better to avoid them if nbproc is greater than 1. The effect is that if the new process fails to start, only one of the old ones will be able to rebind to the socket. - 'fd@<n>' -> use file descriptor <n> inherited from the parent. The fd must be bound and may or may not already be listening. Any part of the address string may reference any number of environment variables by preceding their name with a dollar sign ('$') and optionally enclosing them with braces ('{}'), similarly to what is done in Bourne shell. <port_range> is either a unique TCP port, or a port range for which the proxy will accept connections for the IP address specified above. The port is mandatory for TCP listeners. Note that in the case of an IPv6 address, the port is always the number after the last colon (':'). A range can either be : - a numerical port (ex: '80') - a dash-delimited ports range explicitly stating the lower and upper bounds (ex: '2000-2100') which are included in the range. Particular care must be taken against port ranges, because every <address:port> couple consumes one socket (= a file descriptor), so it's easy to consume lots of descriptors with a simple range, and to run out of sockets. Also, each <address:port> couple must be used only once among all instances running on a same system. Please note that binding to ports lower than 1024 generally require particular privileges to start the program, which are independent of the 'uid' parameter. <path> is a UNIX socket path beginning with a slash ('/'). This is alternative to the TCP listening port. Haproxy will then receive UNIX connections on the socket located at this place. The path must begin with a slash and by default is absolute. It can be relative to the prefix defined by "unix-bind" in the global section. Note that the total length of the prefix followed by the socket path cannot exceed some system limits for UNIX sockets, which commonly are set to 107 characters. <param*> is a list of parameters common to all sockets declared on the same line. These numerous parameters depend on OS and build options and have a complete section dedicated to them. Please refer to section 5 to for more details. It is possible to specify a list of address:port combinations delimited by commas. The frontend will then listen on all of these addresses. There is no fixed limit to the number of addresses and ports which can be listened on in a frontend, as well as there is no limit to the number of "bind" statements in a frontend. Example : listen http_proxy bind :80,:443 bind 10.0.0.1:10080,10.0.0.1:10443 bind /var/run/ssl-frontend.sock user root mode 600 accept-proxy listen http_https_proxy bind :80 bind :443 ssl crt /etc/haproxy/site.pem listen http_https_proxy_explicit bind ipv6@:80 bind ipv4@public_ssl:443 ssl crt /etc/haproxy/site.pem bind unix@ssl-frontend.sock user root mode 600 accept-proxy listen external_bind_app1 bind fd@${FD_APP1} See also : "source", "option forwardfor", "unix-bind" and the PROXY protocol documentation, and section 5 about bind options. bind-process [ all | odd | even | <number 1-64>[-<number 1-64>] ] ... Limit visibility of an instance to a certain set of processes numbers. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : all All process will see this instance. This is the default. It may be used to override a default value. odd This instance will be enabled on processes 1,3,5,...63. This option may be combined with other numbers. even This instance will be enabled on processes 2,4,6,...64. This option may be combined with other numbers. Do not use it with less than 2 processes otherwise some instances might be missing from all processes. number The instance will be enabled on this process number or range, whose values must all be between 1 and 32 or 64 depending on the machine's word size. If a proxy is bound to process numbers greater than the configured global.nbproc, it will either be forced to process #1 if a single process was specified, or to all processes otherwise. This keyword limits binding of certain instances to certain processes. This is useful in order not to have too many processes listening to the same ports. For instance, on a dual-core machine, it might make sense to set 'nbproc 2' in the global section, then distributes the listeners among 'odd' and 'even' instances. At the moment, it is not possible to reference more than 32 or 64 processes using this keyword, but this should be more than enough for most setups. Please note that 'all' really means all processes regardless of the machine's word size, and is not limited to the first 32 or 64. Each "bind" line may further be limited to a subset of the proxy's processes, please consult the "process" bind keyword in section 5.1. When a frontend has no explicit "bind-process" line, it tries to bind to all the processes referenced by its "bind" lines. That means that frontends can easily adapt to their listeners' processes. If some backends are referenced by frontends bound to other processes, the backend automatically inherits the frontend's processes. Example : listen app_ip1 bind 10.0.0.1:80 bind-process odd listen app_ip2 bind 10.0.0.2:80 bind-process even listen management bind 10.0.0.3:80 bind-process 1 2 3 4 listen management bind 10.0.0.4:80 bind-process 1-4 See also : "nbproc" in global section, and "process" in section 5.1. block { if | unless } <condition> Block a layer 7 request if/unless a condition is matched May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes The HTTP request will be blocked very early in the layer 7 processing if/unless <condition> is matched. A 403 error will be returned if the request is blocked. The condition has to reference ACLs (see section 7). This is typically used to deny access to certain sensitive resources if some conditions are met or not met. There is no fixed limit to the number of "block" statements per instance. Example: acl invalid_src src 0.0.0.0/7 224.0.0.0/3 acl invalid_src src_port 0:1023 acl local_dst hdr(host) -i localhost block if invalid_src || local_dst See section 7 about ACL usage. capture cookie <name> len <length> Capture and log a cookie in the request and in the response. May be used in sections : defaults | frontend | listen | backend no | yes | yes | no Arguments : <name> is the beginning of the name of the cookie to capture. In order to match the exact name, simply suffix the name with an equal sign ('='). The full name will appear in the logs, which is useful with application servers which adjust both the cookie name and value (eg: ASPSESSIONXXXXX). <length> is the maximum number of characters to report in the logs, which include the cookie name, the equal sign and the value, all in the standard "name=value" form. The string will be truncated on the right if it exceeds <length>. Only the first cookie is captured. Both the "cookie" request headers and the "set-cookie" response headers are monitored. This is particularly useful to check for application bugs causing session crossing or stealing between users, because generally the user's cookies can only change on a login page. When the cookie was not presented by the client, the associated log column will report "-". When a request does not cause a cookie to be assigned by the server, a "-" is reported in the response column. The capture is performed in the frontend only because it is necessary that the log format does not change for a given frontend depending on the backends. This may change in the future. Note that there can be only one "capture cookie" statement in a frontend. The maximum capture length is set by the global "tune.http.cookielen" setting and defaults to 63 characters. It is not possible to specify a capture in a "defaults" section. Example: capture cookie ASPSESSION len 32 See also : "capture request header", "capture response header" as well as section 8 about logging. capture request header <name> len <length> Capture and log the last occurrence of the specified request header. May be used in sections : defaults | frontend | listen | backend no | yes | yes | no Arguments : <name> is the name of the header to capture. The header names are not case-sensitive, but it is a common practice to write them as they appear in the requests, with the first letter of each word in upper case. The header name will not appear in the logs, only the value is reported, but the position in the logs is respected. <length> is the maximum number of characters to extract from the value and report in the logs. The string will be truncated on the right if it exceeds <length>. The complete value of the last occurrence of the header is captured. The value will be added to the logs between braces ('{}'). If multiple headers are captured, they will be delimited by a vertical bar ('|') and will appear in the same order they were declared in the configuration. Non-existent headers will be logged just as an empty string. Common uses for request header captures include the "Host" field in virtual hosting environments, the "Content-length" when uploads are supported, "User-agent" to quickly differentiate between real users and robots, and "X-Forwarded-For" in proxied environments to find where the request came from. Note that when capturing headers such as "User-agent", some spaces may be logged, making the log analysis more difficult. Thus be careful about what you log if you know your log parser is not smart enough to rely on the braces. There is no limit to the number of captured request headers nor to their length, though it is wise to keep them low to limit memory usage per session. In order to keep log format consistent for a same frontend, header captures can only be declared in a frontend. It is not possible to specify a capture in a "defaults" section. Example: capture request header Host len 15 capture request header X-Forwarded-For len 15 capture request header Referrer len 15 See also : "capture cookie", "capture response header" as well as section 8 about logging. capture response header <name> len <length> Capture and log the last occurrence of the specified response header. May be used in sections : defaults | frontend | listen | backend no | yes | yes | no Arguments : <name> is the name of the header to capture. The header names are not case-sensitive, but it is a common practice to write them as they appear in the response, with the first letter of each word in upper case. The header name will not appear in the logs, only the value is reported, but the position in the logs is respected. <length> is the maximum number of characters to extract from the value and report in the logs. The string will be truncated on the right if it exceeds <length>. The complete value of the last occurrence of the header is captured. The result will be added to the logs between braces ('{}') after the captured request headers. If multiple headers are captured, they will be delimited by a vertical bar ('|') and will appear in the same order they were declared in the configuration. Non-existent headers will be logged just as an empty string. Common uses for response header captures include the "Content-length" header which indicates how many bytes are expected to be returned, the "Location" header to track redirections. There is no limit to the number of captured response headers nor to their length, though it is wise to keep them low to limit memory usage per session. In order to keep log format consistent for a same frontend, header captures can only be declared in a frontend. It is not possible to specify a capture in a "defaults" section. Example: capture response header Content-length len 9 capture response header Location len 15 See also : "capture cookie", "capture request header" as well as section 8 about logging. clitimeout <timeout> (deprecated) Set the maximum inactivity time on the client side. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <timeout> is the timeout value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. The inactivity timeout applies when the client is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase, when the client sends the request, and during the response while it is reading data sent by the server. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. It is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). This parameter is specific to frontends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter is provided for compatibility but is currently deprecated. Please use "timeout client" instead. See also : "timeout client", "timeout http-request", "timeout server", and "srvtimeout". compression algo <algorithm> ... compression type <mime type> ... compression offload Enable HTTP compression. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : algo is followed by the list of supported compression algorithms. type is followed by the list of MIME types that will be compressed. offload makes haproxy work as a compression offloader only (see notes). The currently supported algorithms are : identity this is mostly for debugging, and it was useful for developing the compression feature. Identity does not apply any change on data. gzip applies gzip compression. This setting is only available when support for zlib was built in. deflate same as gzip, but with deflate algorithm and zlib format. Note that this algorithm has ambiguous support on many browsers and no support at all from recent ones. It is strongly recommended not to use it for anything else than experimentation. This setting is only available when support for zlib was built in. Compression will be activated depending on the Accept-Encoding request header. With identity, it does not take care of that header. If backend servers support HTTP compression, these directives will be no-op: haproxy will see the compressed response and will not compress again. If backend servers do not support HTTP compression and there is Accept-Encoding header in request, haproxy will compress the matching response. The "offload" setting makes haproxy remove the Accept-Encoding header to prevent backend servers from compressing responses. It is strongly recommended not to do this because this means that all the compression work will be done on the single point where haproxy is located. However in some deployment scenarios, haproxy may be installed in front of a buggy gateway with broken HTTP compression implementation which can't be turned off. In that case haproxy can be used to prevent that gateway from emitting invalid payloads. In this case, simply removing the header in the configuration does not work because it applies before the header is parsed, so that prevents haproxy from compressing. The "offload" setting should then be used for such scenarios. Note: for now, the "offload" setting is ignored when set in a defaults section. Compression is disabled when: * the request does not advertise a supported compression algorithm in the "Accept-Encoding" header * the response message is not HTTP/1.1 * HTTP status code is not 200 * response header "Transfer-Encoding" contains "chunked" (Temporary Workaround) * response contain neither a "Content-Length" header nor a "Transfer-Encoding" whose last value is "chunked" * response contains a "Content-Type" header whose first value starts with "multipart" * the response contains the "no-transform" value in the "Cache-control" header * User-Agent matches "Mozilla/4" unless it is MSIE 6 with XP SP2, or MSIE 7 and later * The response contains a "Content-Encoding" header, indicating that the response is already compressed (see compression offload) Note: The compression does not rewrite Etag headers, and does not emit the Warning header. Examples : compression algo gzip compression type text/html text/plain contimeout <timeout> (deprecated) Set the maximum time to wait for a connection attempt to a server to succeed. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <timeout> is the timeout value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. If the server is located on the same LAN as haproxy, the connection should be immediate (less than a few milliseconds). Anyway, it is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). By default, the connect timeout also presets the queue timeout to the same value if this one has not been specified. Historically, the contimeout was also used to set the tarpit timeout in a listen section, which is not possible in a pure frontend. This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of failed sessions in the system if the system's timeouts are not configured either. This parameter is provided for backwards compatibility but is currently deprecated. Please use "timeout connect", "timeout queue" or "timeout tarpit" instead. See also : "timeout connect", "timeout queue", "timeout tarpit", "timeout server", "contimeout". cookie <name> [ rewrite | insert | prefix ] [ indirect ] [ nocache ] [ postonly ] [ preserve ] [ httponly ] [ secure ] [ domain <domain> ]* [ maxidle <idle> ] [ maxlife <life> ] Enable cookie-based persistence in a backend. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <name> is the name of the cookie which will be monitored, modified or inserted in order to bring persistence. This cookie is sent to the client via a "Set-Cookie" header in the response, and is brought back by the client in a "Cookie" header in all requests. Special care should be taken to choose a name which does not conflict with any likely application cookie. Also, if the same backends are subject to be used by the same clients (eg: HTTP/HTTPS), care should be taken to use different cookie names between all backends if persistence between them is not desired. rewrite This keyword indicates that the cookie will be provided by the server and that haproxy will have to modify its value to set the server's identifier in it. This mode is handy when the management of complex combinations of "Set-cookie" and "Cache-control" headers is left to the application. The application can then decide whether or not it is appropriate to emit a persistence cookie. Since all responses should be monitored, this mode only works in HTTP close mode. Unless the application behaviour is very complex and/or broken, it is advised not to start with this mode for new deployments. This keyword is incompatible with "insert" and "prefix". insert This keyword indicates that the persistence cookie will have to be inserted by haproxy in server responses if the client did not already have a cookie that would have permitted it to access this server. When used without the "preserve" option, if the server emits a cookie with the same name, it will be remove before processing. For this reason, this mode can be used to upgrade existing configurations running in the "rewrite" mode. The cookie will only be a session cookie and will not be stored on the client's disk. By default, unless the "indirect" option is added, the server will see the cookies emitted by the client. Due to caching effects, it is generally wise to add the "nocache" or "postonly" keywords (see below). The "insert" keyword is not compatible with "rewrite" and "prefix". prefix This keyword indicates that instead of relying on a dedicated cookie for the persistence, an existing one will be completed. This may be needed in some specific environments where the client does not support more than one single cookie and the application already needs it. In this case, whenever the server sets a cookie named <name>, it will be prefixed with the server's identifier and a delimiter. The prefix will be removed from all client requests so that the server still finds the cookie it emitted. Since all requests and responses are subject to being modified, this mode requires the HTTP close mode. The "prefix" keyword is not compatible with "rewrite" and "insert". Note: it is highly recommended not to use "indirect" with "prefix", otherwise server cookie updates would not be sent to clients. indirect When this option is specified, no cookie will be emitted to a client which already has a valid one for the server which has processed the request. If the server sets such a cookie itself, it will be removed, unless the "preserve" option is also set. In "insert" mode, this will additionally remove cookies from the requests transmitted to the server, making the persistence mechanism totally transparent from an application point of view. Note: it is highly recommended not to use "indirect" with "prefix", otherwise server cookie updates would not be sent to clients. nocache This option is recommended in conjunction with the insert mode when there is a cache between the client and HAProxy, as it ensures that a cacheable response will be tagged non-cacheable if a cookie needs to be inserted. This is important because if all persistence cookies are added on a cacheable home page for instance, then all customers will then fetch the page from an outer cache and will all share the same persistence cookie, leading to one server receiving much more traffic than others. See also the "insert" and "postonly" options. postonly This option ensures that cookie insertion will only be performed on responses to POST requests. It is an alternative to the "nocache" option, because POST responses are not cacheable, so this ensures that the persistence cookie will never get cached. Since most sites do not need any sort of persistence before the first POST which generally is a login request, this is a very efficient method to optimize caching without risking to find a persistence cookie in the cache. See also the "insert" and "nocache" options. preserve This option may only be used with "insert" and/or "indirect". It allows the server to emit the persistence cookie itself. In this case, if a cookie is found in the response, haproxy will leave it untouched. This is useful in order to end persistence after a logout request for instance. For this, the server just has to emit a cookie with an invalid value (eg: empty) or with a date in the past. By combining this mechanism with the "disable-on-404" check option, it is possible to perform a completely graceful shutdown because users will definitely leave the server after they logout. httponly This option tells haproxy to add an "HttpOnly" cookie attribute when a cookie is inserted. This attribute is used so that a user agent doesn't share the cookie with non-HTTP components. Please check RFC6265 for more information on this attribute. secure This option tells haproxy to add a "Secure" cookie attribute when a cookie is inserted. This attribute is used so that a user agent never emits this cookie over non-secure channels, which means that a cookie learned with this flag will be presented only over SSL/TLS connections. Please check RFC6265 for more information on this attribute. domain This option allows to specify the domain at which a cookie is inserted. It requires exactly one parameter: a valid domain name. If the domain begins with a dot, the browser is allowed to use it for any host ending with that name. It is also possible to specify several domain names by invoking this option multiple times. Some browsers might have small limits on the number of domains, so be careful when doing that. For the record, sending 10 domains to MSIE 6 or Firefox 2 works as expected. maxidle This option allows inserted cookies to be ignored after some idle time. It only works with insert-mode cookies. When a cookie is sent to the client, the date this cookie was emitted is sent too. Upon further presentations of this cookie, if the date is older than the delay indicated by the parameter (in seconds), it will be ignored. Otherwise, it will be refreshed if needed when the response is sent to the client. This is particularly useful to prevent users who never close their browsers from remaining for too long on the same server (eg: after a farm size change). When this option is set and a cookie has no date, it is always accepted, but gets refreshed in the response. This maintains the ability for admins to access their sites. Cookies that have a date in the future further than 24 hours are ignored. Doing so lets admins fix timezone issues without risking kicking users off the site. maxlife This option allows inserted cookies to be ignored after some life time, whether they're in use or not. It only works with insert mode cookies. When a cookie is first sent to the client, the date this cookie was emitted is sent too. Upon further presentations of this cookie, if the date is older than the delay indicated by the parameter (in seconds), it will be ignored. If the cookie in the request has no date, it is accepted and a date will be set. Cookies that have a date in the future further than 24 hours are ignored. Doing so lets admins fix timezone issues without risking kicking users off the site. Contrary to maxidle, this value is not refreshed, only the first visit date counts. Both maxidle and maxlife may be used at the time. This is particularly useful to prevent users who never close their browsers from remaining for too long on the same server (eg: after a farm size change). This is stronger than the maxidle method in that it forces a redispatch after some absolute delay. There can be only one persistence cookie per HTTP backend, and it can be declared in a defaults section. The value of the cookie will be the value indicated after the "cookie" keyword in a "server" statement. If no cookie is declared for a given server, the cookie is not set. Examples : cookie JSESSIONID prefix cookie SRV insert indirect nocache cookie SRV insert postonly indirect cookie SRV insert indirect nocache maxidle 30m maxlife 8h See also : "appsession", "balance source", "capture cookie", "server" and "ignore-persist". default-server [param*] Change default options for a server in a backend May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments: <param*> is a list of parameters for this server. The "default-server" keyword accepts an important number of options and has a complete section dedicated to it. Please refer to section 5 for more details. Example : default-server inter 1000 weight 13 See also: "server" and section 5 about server options default_backend <backend> Specify the backend to use when no "use_backend" rule has been matched. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <backend> is the name of the backend to use. When doing content-switching between frontend and backends using the "use_backend" keyword, it is often useful to indicate which backend will be used when no rule has matched. It generally is the dynamic backend which will catch all undetermined requests. Example : use_backend dynamic if url_dyn use_backend static if url_css url_img extension_img default_backend dynamic See also : "use_backend", "reqsetbe", "reqisetbe" description <string> Describe a listen, frontend or backend. May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : string Allows to add a sentence to describe the related object in the HAProxy HTML stats page. The description will be printed on the right of the object name it describes. No need to backslash spaces in the <string> arguments. disabled Disable a proxy, frontend or backend. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none The "disabled" keyword is used to disable an instance, mainly in order to liberate a listening port or to temporarily disable a service. The instance will still be created and its configuration will be checked, but it will be created in the "stopped" state and will appear as such in the statistics. It will not receive any traffic nor will it send any health-checks or logs. It is possible to disable many instances at once by adding the "disabled" keyword in a "defaults" section. See also : "enabled" dispatch <address>:<port> Set a default server address May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <address> is the IPv4 address of the default server. Alternatively, a resolvable hostname is supported, but this name will be resolved during start-up. <ports> is a mandatory port specification. All connections will be sent to this port, and it is not permitted to use port offsets as is possible with normal servers. The "dispatch" keyword designates a default server for use when no other server can take the connection. In the past it was used to forward non persistent connections to an auxiliary load balancer. Due to its simple syntax, it has also been used for simple TCP relays. It is recommended not to use it for more clarity, and to use the "server" directive instead. See also : "server" enabled Enable a proxy, frontend or backend. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none The "enabled" keyword is used to explicitly enable an instance, when the defaults has been set to "disabled". This is very rarely used. See also : "disabled" errorfile <code> <file> Return a file contents instead of errors generated by HAProxy May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <code> is the HTTP status code. Currently, HAProxy is capable of generating codes 200, 400, 403, 408, 500, 502, 503, and 504. <file> designates a file containing the full HTTP response. It is recommended to follow the common practice of appending ".http" to the filename so that people do not confuse the response with HTML error pages, and to use absolute paths, since files are read before any chroot is performed. It is important to understand that this keyword is not meant to rewrite errors returned by the server, but errors detected and returned by HAProxy. This is why the list of supported errors is limited to a small set. Code 200 is emitted in response to requests matching a "monitor-uri" rule. The files are returned verbatim on the TCP socket. This allows any trick such as redirections to another URL or site, as well as tricks to clean cookies, force enable or disable caching, etc... The package provides default error files returning the same contents as default errors. The files should not exceed the configured buffer size (BUFSIZE), which generally is 8 or 16 kB, otherwise they will be truncated. It is also wise not to put any reference to local contents (eg: images) in order to avoid loops between the client and HAProxy when all servers are down, causing an error to be returned instead of an image. For better HTTP compliance, it is recommended that all header lines end with CR-LF and not LF alone. The files are read at the same time as the configuration and kept in memory. For this reason, the errors continue to be returned even when the process is chrooted, and no file change is considered while the process is running. A simple method for developing those files consists in associating them to the 403 status code and interrogating a blocked URL. See also : "errorloc", "errorloc302", "errorloc303" Example : errorfile 400 /etc/haproxy/errorfiles/400badreq.http errorfile 408 /dev/null # workaround Chrome pre-connect bug errorfile 403 /etc/haproxy/errorfiles/403forbid.http errorfile 503 /etc/haproxy/errorfiles/503sorry.http errorloc <code> <url> errorloc302 <code> <url> Return an HTTP redirection to a URL instead of errors generated by HAProxy May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <code> is the HTTP status code. Currently, HAProxy is capable of generating codes 200, 400, 403, 408, 500, 502, 503, and 504. <url> it is the exact contents of the "Location" header. It may contain either a relative URI to an error page hosted on the same site, or an absolute URI designating an error page on another site. Special care should be given to relative URIs to avoid redirect loops if the URI itself may generate the same error (eg: 500). It is important to understand that this keyword is not meant to rewrite errors returned by the server, but errors detected and returned by HAProxy. This is why the list of supported errors is limited to a small set. Code 200 is emitted in response to requests matching a "monitor-uri" rule. Note that both keyword return the HTTP 302 status code, which tells the client to fetch the designated URL using the same HTTP method. This can be quite problematic in case of non-GET methods such as POST, because the URL sent to the client might not be allowed for something other than GET. To workaround this problem, please use "errorloc303" which send the HTTP 303 status code, indicating to the client that the URL must be fetched with a GET request. See also : "errorfile", "errorloc303" errorloc303 <code> <url> Return an HTTP redirection to a URL instead of errors generated by HAProxy May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <code> is the HTTP status code. Currently, HAProxy is capable of generating codes 400, 403, 408, 500, 502, 503, and 504. <url> it is the exact contents of the "Location" header. It may contain either a relative URI to an error page hosted on the same site, or an absolute URI designating an error page on another site. Special care should be given to relative URIs to avoid redirect loops if the URI itself may generate the same error (eg: 500). It is important to understand that this keyword is not meant to rewrite errors returned by the server, but errors detected and returned by HAProxy. This is why the list of supported errors is limited to a small set. Code 200 is emitted in response to requests matching a "monitor-uri" rule. Note that both keyword return the HTTP 303 status code, which tells the client to fetch the designated URL using the same HTTP GET method. This solves the usual problems associated with "errorloc" and the 302 code. It is possible that some very old browsers designed before HTTP/1.1 do not support it, but no such problem has been reported till now. See also : "errorfile", "errorloc", "errorloc302" force-persist { if | unless } <condition> Declare a condition to force persistence on down servers May be used in sections: defaults | frontend | listen | backend no | yes | yes | yes By default, requests are not dispatched to down servers. It is possible to force this using "option persist", but it is unconditional and redispatches to a valid server if "option redispatch" is set. That leaves with very little possibilities to force some requests to reach a server which is artificially marked down for maintenance operations. The "force-persist" statement allows one to declare various ACL-based conditions which, when met, will cause a request to ignore the down status of a server and still try to connect to it. That makes it possible to start a server, still replying an error to the health checks, and run a specially configured browser to test the service. Among the handy methods, one could use a specific source IP address, or a specific cookie. The cookie also has the advantage that it can easily be added/removed on the browser from a test page. Once the service is validated, it is then possible to open the service to the world by returning a valid response to health checks. The forced persistence is enabled when an "if" condition is met, or unless an "unless" condition is met. The final redispatch is always disabled when this is used. See also : "option redispatch", "ignore-persist", "persist", and section 7 about ACL usage. fullconn <conns> Specify at what backend load the servers will reach their maxconn May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <conns> is the number of connections on the backend which will make the servers use the maximal number of connections. When a server has a "maxconn" parameter specified, it means that its number of concurrent connections will never go higher. Additionally, if it has a "minconn" parameter, it indicates a dynamic limit following the backend's load. The server will then always accept at least <minconn> connections, never more than <maxconn>, and the limit will be on the ramp between both values when the backend has less than <conns> concurrent connections. This makes it possible to limit the load on the servers during normal loads, but push it further for important loads without overloading the servers during exceptional loads. Since it's hard to get this value right, haproxy automatically sets it to 10% of the sum of the maxconns of all frontends that may branch to this backend (based on "use_backend" and "default_backend" rules). That way it's safe to leave it unset. However, "use_backend" involving dynamic names are not counted since there is no way to know if they could match or not. Example : # The servers will accept between 100 and 1000 concurrent connections each # and the maximum of 1000 will be reached when the backend reaches 10000 # connections. backend dynamic fullconn 10000 server srv1 dyn1:80 minconn 100 maxconn 1000 server srv2 dyn2:80 minconn 100 maxconn 1000 See also : "maxconn", "server" grace <time> Maintain a proxy operational for some time after a soft stop May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <time> is the time (by default in milliseconds) for which the instance will remain operational with the frontend sockets still listening when a soft-stop is received via the SIGUSR1 signal. This may be used to ensure that the services disappear in a certain order. This was designed so that frontends which are dedicated to monitoring by an external equipment fail immediately while other ones remain up for the time needed by the equipment to detect the failure. Note that currently, there is very little benefit in using this parameter, and it may in fact complicate the soft-reconfiguration process more than simplify it. hash-type <method> <function> <modifier> Specify a method to use for mapping hashes to servers May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <method> is the method used to select a server from the hash computed by the <function> : map-based the hash table is a static array containing all alive servers. The hashes will be very smooth, will consider weights, but will be static in that weight changes while a server is up will be ignored. This means that there will be no slow start. Also, since a server is selected by its position in the array, most mappings are changed when the server count changes. This means that when a server goes up or down, or when a server is added to a farm, most connections will be redistributed to different servers. This can be inconvenient with caches for instance. consistent the hash table is a tree filled with many occurrences of each server. The hash key is looked up in the tree and the closest server is chosen. This hash is dynamic, it supports changing weights while the servers are up, so it is compatible with the slow start feature. It has the advantage that when a server goes up or down, only its associations are moved. When a server is added to the farm, only a few part of the mappings are redistributed, making it an ideal method for caches. However, due to its principle, the distribution will never be very smooth and it may sometimes be necessary to adjust a server's weight or its ID to get a more balanced distribution. In order to get the same distribution on multiple load balancers, it is important that all servers have the exact same IDs. Note: consistent hash uses sdbm and avalanche if no hash function is specified. <function> is the hash function to be used : sdbm this function was created initially for sdbm (a public-domain reimplementation of ndbm) database library. It was found to do well in scrambling bits, causing better distribution of the keys and fewer splits. It also happens to be a good general hashing function with good distribution, unless the total server weight is a multiple of 64, in which case applying the avalanche modifier may help. djb2 this function was first proposed by Dan Bernstein many years ago on comp.lang.c. Studies have shown that for certain workload this function provides a better distribution than sdbm. It generally works well with text-based inputs though it can perform extremely poorly with numeric-only input or when the total server weight is a multiple of 33, unless the avalanche modifier is also used. wt6 this function was designed for haproxy while testing other functions in the past. It is not as smooth as the other ones, but is much less sensible to the input data set or to the number of servers. It can make sense as an alternative to sdbm+avalanche or djb2+avalanche for consistent hashing or when hashing on numeric data such as a source IP address or a visitor identifier in a URL parameter. <modifier> indicates an optional method applied after hashing the key : avalanche This directive indicates that the result from the hash function above should not be used in its raw form but that a 4-byte full avalanche hash must be applied first. The purpose of this step is to mix the resulting bits from the previous hash in order to avoid any undesired effect when the input contains some limited values or when the number of servers is a multiple of one of the hash's components (64 for SDBM, 33 for DJB2). Enabling avalanche tends to make the result less predictable, but it's also not as smooth as when using the original function. Some testing might be needed with some workloads. This hash is one of the many proposed by Bob Jenkins. The default hash type is "map-based" and is recommended for most usages. The default function is "sdbm", the selection of a function should be based on the range of the values being hashed. See also : "balance", "server" http-check disable-on-404 Enable a maintenance mode upon HTTP/404 response to health-checks May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none When this option is set, a server which returns an HTTP code 404 will be excluded from further load-balancing, but will still receive persistent connections. This provides a very convenient method for Web administrators to perform a graceful shutdown of their servers. It is also important to note that a server which is detected as failed while it was in this mode will not generate an alert, just a notice. If the server responds 2xx or 3xx again, it will immediately be reinserted into the farm. The status on the stats page reports "NOLB" for a server in this mode. It is important to note that this option only works in conjunction with the "httpchk" option. If this option is used with "http-check expect", then it has precedence over it so that 404 responses will still be considered as soft-stop. See also : "option httpchk", "http-check expect" http-check expect [!] <match> <pattern> Make HTTP health checks consider response contents or specific status codes May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <match> is a keyword indicating how to look for a specific pattern in the response. The keyword may be one of "status", "rstatus", "string", or "rstring". The keyword may be preceded by an exclamation mark ("!") to negate the match. Spaces are allowed between the exclamation mark and the keyword. See below for more details on the supported keywords. <pattern> is the pattern to look for. It may be a string or a regular expression. If the pattern contains spaces, they must be escaped with the usual backslash ('\'). By default, "option httpchk" considers that response statuses 2xx and 3xx are valid, and that others are invalid. When "http-check expect" is used, it defines what is considered valid or invalid. Only one "http-check" statement is supported in a backend. If a server fails to respond or times out, the check obviously fails. The available matches are : status <string> : test the exact string match for the HTTP status code. A health check response will be considered valid if the response's status code is exactly this string. If the "status" keyword is prefixed with "!", then the response will be considered invalid if the status code matches. rstatus <regex> : test a regular expression for the HTTP status code. A health check response will be considered valid if the response's status code matches the expression. If the "rstatus" keyword is prefixed with "!", then the response will be considered invalid if the status code matches. This is mostly used to check for multiple codes. string <string> : test the exact string match in the HTTP response body. A health check response will be considered valid if the response's body contains this exact string. If the "string" keyword is prefixed with "!", then the response will be considered invalid if the body contains this string. This can be used to look for a mandatory word at the end of a dynamic page, or to detect a failure when a specific error appears on the check page (eg: a stack trace). rstring <regex> : test a regular expression on the HTTP response body. A health check response will be considered valid if the response's body matches this expression. If the "rstring" keyword is prefixed with "!", then the response will be considered invalid if the body matches the expression. This can be used to look for a mandatory word at the end of a dynamic page, or to detect a failure when a specific error appears on the check page (eg: a stack trace). It is important to note that the responses will be limited to a certain size defined by the global "tune.chksize" option, which defaults to 16384 bytes. Thus, too large responses may not contain the mandatory pattern when using "string" or "rstring". If a large response is absolutely required, it is possible to change the default max size by setting the global variable. However, it is worth keeping in mind that parsing very large responses can waste some CPU cycles, especially when regular expressions are used, and that it is always better to focus the checks on smaller resources. Also "http-check expect" doesn't support HTTP keep-alive. Keep in mind that it will automatically append a "Connection: close" header, meaning that this header should not be present in the request provided by "option httpchk". Last, if "http-check expect" is combined with "http-check disable-on-404", then this last one has precedence when the server responds with 404. Examples : # only accept status 200 as valid http-check expect status 200 # consider SQL errors as errors http-check expect ! string SQL\ Error # consider status 5xx only as errors http-check expect ! rstatus ^5 # check that we have a correct hexadecimal tag before /html http-check expect rstring <!--tag:[0-9a-f]*</html> See also : "option httpchk", "http-check disable-on-404" http-check send-state Enable emission of a state header with HTTP health checks May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none When this option is set, haproxy will systematically send a special header "X-Haproxy-Server-State" with a list of parameters indicating to each server how they are seen by haproxy. This can be used for instance when a server is manipulated without access to haproxy and the operator needs to know whether haproxy still sees it up or not, or if the server is the last one in a farm. The header is composed of fields delimited by semi-colons, the first of which is a word ("UP", "DOWN", "NOLB"), possibly followed by a number of valid checks on the total number before transition, just as appears in the stats interface. Next headers are in the form "<variable>=<value>", indicating in no specific order some values available in the stats interface : - a variable "name", containing the name of the backend followed by a slash ("/") then the name of the server. This can be used when a server is checked in multiple backends. - a variable "node" containing the name of the haproxy node, as set in the global "node" variable, otherwise the system's hostname if unspecified. - a variable "weight" indicating the weight of the server, a slash ("/") and the total weight of the farm (just counting usable servers). This helps to know if other servers are available to handle the load when this one fails. - a variable "scur" indicating the current number of concurrent connections on the server, followed by a slash ("/") then the total number of connections on all servers of the same backend. - a variable "qcur" indicating the current number of requests in the server's queue. Example of a header received by the application server : >>> X-Haproxy-Server-State: UP 2/3; name=bck/srv2; node=lb1; weight=1/2; \ scur=13/22; qcur=0 See also : "option httpchk", "http-check disable-on-404" http-request { allow | deny | tarpit | auth [realm <realm>] | redirect <rule> | add-header <name> <fmt> | set-header <name> <fmt> | del-header <name> | set-nice <nice> | set-log-level <level> | replace-header <name> <match-regex> <replace-fmt> | replace-value <name> <match-regex> <replace-fmt> | set-tos <tos> | set-mark <mark> | add-acl(<file name>) <key fmt> | del-acl(<file name>) <key fmt> | del-map(<file name>) <key fmt> | set-map(<file name>) <key fmt> <value fmt> } [ { if | unless } <condition> ] Access control for Layer 7 requests May be used in sections: defaults | frontend | listen | backend no | yes | yes | yes The http-request statement defines a set of rules which apply to layer 7 processing. The rules are evaluated in their declaration order when they are met in a frontend, listen or backend section. Any rule may optionally be followed by an ACL-based condition, in which case it will only be evaluated if the condition is true. The first keyword is the rule's action. Currently supported actions include : - "allow" : this stops the evaluation of the rules and lets the request pass the check. No further "http-request" rules are evaluated. - "deny" : this stops the evaluation of the rules and immediately rejects the request and emits an HTTP 403 error. No further "http-request" rules are evaluated. - "tarpit" : this stops the evaluation of the rules and immediately blocks the request without responding for a delay specified by "timeout tarpit" or "timeout connect" if the former is not set. After that delay, if the client is still connected, an HTTP error 500 is returned so that the client does not suspect it has been tarpitted. Logs will report the flags "PT". The goal of the tarpit rule is to slow down robots during an attack when they're limited on the number of concurrent requests. It can be very efficient against very dumb robots, and will significantly reduce the load on firewalls compared to a "deny" rule. But when facing "correctly" developed robots, it can make things worse by forcing haproxy and the front firewall to support insane number of concurrent connections. - "auth" : this stops the evaluation of the rules and immediately responds with an HTTP 401 or 407 error code to invite the user to present a valid user name and password. No further "http-request" rules are evaluated. An optional "realm" parameter is supported, it sets the authentication realm that is returned with the response (typically the application's name). - "redirect" : this performs an HTTP redirection based on a redirect rule. This is exactly the same as the "redirect" statement except that it inserts a redirect rule which can be processed in the middle of other "http-request" rules and that these rules use the "log-format" strings. See the "redirect" keyword for the rule's syntax. - "add-header" appends an HTTP header field whose name is specified in <name> and whose value is defined by <fmt> which follows the log-format rules (see Custom Log Format in section 8.2.4). This is particularly useful to pass connection-specific information to the server (eg: the client's SSL certificate), or to combine several headers into one. This rule is not final, so it is possible to add other similar rules. Note that header addition is performed immediately, so one rule might reuse the resulting header from a previous rule. - "set-header" does the same as "add-header" except that the header name is first removed if it existed. This is useful when passing security information to the server, where the header must not be manipulated by external users. Note that the new value is computed before the removal so it is possible to concatenate a value to an existing header. - "del-header" removes all HTTP header fields whose name is specified in <name>. - "replace-header" matches the regular expression in all occurrences of header field <name> according to <match-regex>, and replaces them with the <replace-fmt> argument. Format characters are allowed in replace-fmt and work like in <fmt> arguments in "add-header". The match is only case-sensitive. It is important to understand that this action only considers whole header lines, regardless of the number of values they may contain. This usage is suited to headers naturally containing commas in their value, such as If-Modified-Since and so on. Example: http-request replace-header Cookie foo=([^;]*);(.*) foo=\1;ip=%bi;\2 applied to: Cookie: foo=foobar; expires=Tue, 14-Jun-2016 01:40:45 GMT; outputs: Cookie: foo=foobar;ip=192.168.1.20; expires=Tue, 14-Jun-2016 01:40:45 GMT; assuming the backend IP is 192.168.1.20 - "replace-value" works like "replace-header" except that it matches the regex against every comma-delimited value of the header field <name> instead of the entire header. This is suited for all headers which are allowed to carry more than one value. An example could be the Accept header. Example: http-request replace-value X-Forwarded-For ^192\.168\.(.*)$ 172.16.\1 applied to: X-Forwarded-For: 192.168.10.1, 192.168.13.24, 10.0.0.37 outputs: X-Forwarded-For: 172.16.10.1, 172.16.13.24, 10.0.0.37 - "set-nice" sets the "nice" factor of the current request being processed. It only has effect against the other requests being processed at the same time. The default value is 0, unless altered by the "nice" setting on the "bind" line. The accepted range is -1024..1024. The higher the value, the nicest the request will be. Lower values will make the request more important than other ones. This can be useful to improve the speed of some requests, or lower the priority of non-important requests. Using this setting without prior experimentation can cause some major slowdown. - "set-log-level" is used to change the log level of the current request when a certain condition is met. Valid levels are the 8 syslog levels (see the "log" keyword) plus the special level "silent" which disables logging for this request. This rule is not final so the last matching rule wins. This rule can be useful to disable health checks coming from another equipment. - "set-tos" is used to set the TOS or DSCP field value of packets sent to the client to the value passed in <tos> on platforms which support this. This value represents the whole 8 bits of the IP TOS field, and can be expressed both in decimal or hexadecimal format (prefixed by "0x"). Note that only the 6 higher bits are used in DSCP or TOS, and the two lower bits are always 0. This can be used to adjust some routing behaviour on border routers based on some information from the request. See RFC 2474, 2597, 3260 and 4594 for more information. - "set-mark" is used to set the Netfilter MARK on all packets sent to the client to the value passed in <mark> on platforms which support it. This value is an unsigned 32 bit value which can be matched by netfilter and by the routing table. It can be expressed both in decimal or hexadecimal format (prefixed by "0x"). This can be useful to force certain packets to take a different route (for example a cheaper network path for bulk downloads). This works on Linux kernels 2.6.32 and above and requires admin privileges. - "add-acl" is used to add a new entry into an ACL. The ACL must be loaded from a file (even a dummy empty file). The file name of the ACL to be updated is passed between parentheses. It takes one argument: <key fmt>, which follows log-format rules, to collect content of the new entry. It performs a lookup in the ACL before insertion, to avoid duplicated (or more) values. This lookup is done by a linear search and can be expensive with large lists! It is the equivalent of the "add acl" command from the stats socket, but can be triggered by an HTTP request. - "del-acl" is used to delete an entry from an ACL. The ACL must be loaded from a file (even a dummy empty file). The file name of the ACL to be updated is passed between parentheses. It takes one argument: <key fmt>, which follows log-format rules, to collect content of the entry to delete. It is the equivalent of the "del acl" command from the stats socket, but can be triggered by an HTTP request. - "del-map" is used to delete an entry from a MAP. The MAP must be loaded from a file (even a dummy empty file). The file name of the MAP to be updated is passed between parentheses. It takes one argument: <key fmt>, which follows log-format rules, to collect content of the entry to delete. It takes one argument: "file name" It is the equivalent of the "del map" command from the stats socket, but can be triggered by an HTTP request. - "set-map" is used to add a new entry into a MAP. The MAP must be loaded from a file (even a dummy empty file). The file name of the MAP to be updated is passed between parentheses. It takes 2 arguments: <key fmt>, which follows log-format rules, used to collect MAP key, and <value fmt>, which follows log-format rules, used to collect content for the new entry. It performs a lookup in the MAP before insertion, to avoid duplicated (or more) values. This lookup is done by a linear search and can be expensive with large lists! It is the equivalent of the "set map" command from the stats socket, but can be triggered by an HTTP request. There is no limit to the number of http-request statements per instance. It is important to know that http-request rules are processed very early in the HTTP processing, just after "block" rules and before "reqdel" or "reqrep" rules. That way, headers added by "add-header"/"set-header" are visible by almost all further ACL rules. Example: acl nagios src 192.168.129.3 acl local_net src 192.168.0.0/16 acl auth_ok http_auth(L1) http-request allow if nagios http-request allow if local_net auth_ok http-request auth realm Gimme if local_net auth_ok http-request deny Example: acl auth_ok http_auth_group(L1) G1 http-request auth unless auth_ok Example: http-request set-header X-Haproxy-Current-Date %T http-request set-header X-SSL %[ssl_fc] http-request set-header X-SSL-Session_ID %[ssl_fc_session_id] http-request set-header X-SSL-Client-Verify %[ssl_c_verify] http-request set-header X-SSL-Client-DN %{+Q}[ssl_c_s_dn] http-request set-header X-SSL-Client-CN %{+Q}[ssl_c_s_dn(cn)] http-request set-header X-SSL-Issuer %{+Q}[ssl_c_i_dn] http-request set-header X-SSL-Client-NotBefore %{+Q}[ssl_c_notbefore] http-request set-header X-SSL-Client-NotAfter %{+Q}[ssl_c_notafter] Example: acl key req.hdr(X-Add-Acl-Key) -m found acl add path /addacl acl del path /delacl acl myhost hdr(Host) -f myhost.lst http-request add-acl(myhost.lst) %[req.hdr(X-Add-Acl-Key)] if key add http-request del-acl(myhost.lst) %[req.hdr(X-Add-Acl-Key)] if key del Example: acl value req.hdr(X-Value) -m found acl setmap path /setmap acl delmap path /delmap use_backend bk_appli if { hdr(Host),map_str(map.lst) -m found } http-request set-map(map.lst) %[src] %[req.hdr(X-Value)] if setmap value http-request del-map(map.lst) %[src] if delmap See also : "stats http-request", section 3.4 about userlists and section 7 about ACL usage. http-response { allow | deny | add-header <name> <fmt> | set-nice <nice> | set-header <name> <fmt> | del-header <name> | replace-header <name> <regex-match> <replace-fmt> | replace-value <name> <regex-match> <replace-fmt> | set-log-level <level> | set-mark <mark> | set-tos <tos> | add-acl(<file name>) <key fmt> | del-acl(<file name>) <key fmt> | del-map(<file name>) <key fmt> | set-map(<file name>) <key fmt> <value fmt> } [ { if | unless } <condition> ] Access control for Layer 7 responses May be used in sections: defaults | frontend | listen | backend no | yes | yes | yes The http-response statement defines a set of rules which apply to layer 7 processing. The rules are evaluated in their declaration order when they are met in a frontend, listen or backend section. Any rule may optionally be followed by an ACL-based condition, in which case it will only be evaluated if the condition is true. Since these rules apply on responses, the backend rules are applied first, followed by the frontend's rules. The first keyword is the rule's action. Currently supported actions include : - "allow" : this stops the evaluation of the rules and lets the response pass the check. No further "http-response" rules are evaluated for the current section. - "deny" : this stops the evaluation of the rules and immediately rejects the response and emits an HTTP 502 error. No further "http-response" rules are evaluated. - "add-header" appends an HTTP header field whose name is specified in <name> and whose value is defined by <fmt> which follows the log-format rules (see Custom Log Format in section 8.2.4). This may be used to send a cookie to a client for example, or to pass some internal information. This rule is not final, so it is possible to add other similar rules. Note that header addition is performed immediately, so one rule might reuse the resulting header from a previous rule. - "set-header" does the same as "add-header" except that the header name is first removed if it existed. This is useful when passing security information to the server, where the header must not be manipulated by external users. - "del-header" removes all HTTP header fields whose name is specified in <name>. - "replace-header" matches the regular expression in all occurrences of header field <name> according to <match-regex>, and replaces them with the <replace-fmt> argument. Format characters are allowed in replace-fmt and work like in <fmt> arguments in "add-header". The match is only case-sensitive. It is important to understand that this action only considers whole header lines, regardless of the number of values they may contain. This usage is suited to headers naturally containing commas in their value, such as Set-Cookie, Expires and so on. Example: http-response replace-header Set-Cookie (C=[^;]*);(.*) \1;ip=%bi;\2 applied to: Set-Cookie: C=1; expires=Tue, 14-Jun-2016 01:40:45 GMT outputs: Set-Cookie: C=1;ip=192.168.1.20; expires=Tue, 14-Jun-2016 01:40:45 GMT assuming the backend IP is 192.168.1.20. - "replace-value" works like "replace-header" except that it matches the regex against every comma-delimited value of the header field <name> instead of the entire header. This is suited for all headers which are allowed to carry more than one value. An example could be the Accept header. Example: http-response replace-value Cache-control ^public$ private applied to: Cache-Control: max-age=3600, public outputs: Cache-Control: max-age=3600, private - "set-nice" sets the "nice" factor of the current request being processed. It only has effect against the other requests being processed at the same time. The default value is 0, unless altered by the "nice" setting on the "bind" line. The accepted range is -1024..1024. The higher the value, the nicest the request will be. Lower values will make the request more important than other ones. This can be useful to improve the speed of some requests, or lower the priority of non-important requests. Using this setting without prior experimentation can cause some major slowdown. - "set-log-level" is used to change the log level of the current request when a certain condition is met. Valid levels are the 8 syslog levels (see the "log" keyword) plus the special level "silent" which disables logging for this request. This rule is not final so the last matching rule wins. This rule can be useful to disable health checks coming from another equipment. - "set-tos" is used to set the TOS or DSCP field value of packets sent to the client to the value passed in <tos> on platforms which support this. This value represents the whole 8 bits of the IP TOS field, and can be expressed both in decimal or hexadecimal format (prefixed by "0x"). Note that only the 6 higher bits are used in DSCP or TOS, and the two lower bits are always 0. This can be used to adjust some routing behaviour on border routers based on some information from the request. See RFC 2474, 2597, 3260 and 4594 for more information. - "set-mark" is used to set the Netfilter MARK on all packets sent to the client to the value passed in <mark> on platforms which support it. This value is an unsigned 32 bit value which can be matched by netfilter and by the routing table. It can be expressed both in decimal or hexadecimal format (prefixed by "0x"). This can be useful to force certain packets to take a different route (for example a cheaper network path for bulk downloads). This works on Linux kernels 2.6.32 and above and requires admin privileges. - "add-acl" is used to add a new entry into an ACL. The ACL must be loaded from a file (even a dummy empty file). The file name of the ACL to be updated is passed between parentheses. It takes one argument: <key fmt>, which follows log-format rules, to collect content of the new entry. It performs a lookup in the ACL before insertion, to avoid duplicated (or more) values. This lookup is done by a linear search and can be expensive with large lists! It is the equivalent of the "add acl" command from the stats socket, but can be triggered by an HTTP response. - "del-acl" is used to delete an entry from an ACL. The ACL must be loaded from a file (even a dummy empty file). The file name of the ACL to be updated is passed between parentheses. It takes one argument: <key fmt>, which follows log-format rules, to collect content of the entry to delete. It is the equivalent of the "del acl" command from the stats socket, but can be triggered by an HTTP response. - "del-map" is used to delete an entry from a MAP. The MAP must be loaded from a file (even a dummy empty file). The file name of the MAP to be updated is passed between parentheses. It takes one argument: <key fmt>, which follows log-format rules, to collect content of the entry to delete. It takes one argument: "file name" It is the equivalent of the "del map" command from the stats socket, but can be triggered by an HTTP response. - "set-map" is used to add a new entry into a MAP. The MAP must be loaded from a file (even a dummy empty file). The file name of the MAP to be updated is passed between parentheses. It takes 2 arguments: <key fmt>, which follows log-format rules, used to collect MAP key, and <value fmt>, which follows log-format rules, used to collect content for the new entry. It performs a lookup in the MAP before insertion, to avoid duplicated (or more) values. This lookup is done by a linear search and can be expensive with large lists! It is the equivalent of the "set map" command from the stats socket, but can be triggered by an HTTP response. There is no limit to the number of http-response statements per instance. It is important to know that http-response rules are processed very early in the HTTP processing, before "reqdel" or "reqrep" rules. That way, headers added by "add-header"/"set-header" are visible by almost all further ACL rules. Example: acl key_acl res.hdr(X-Acl-Key) -m found acl myhost hdr(Host) -f myhost.lst http-response add-acl(myhost.lst) %[res.hdr(X-Acl-Key)] if key_acl http-response del-acl(myhost.lst) %[res.hdr(X-Acl-Key)] if key_acl Example: acl value res.hdr(X-Value) -m found use_backend bk_appli if { hdr(Host),map_str(map.lst) -m found } http-response set-map(map.lst) %[src] %[res.hdr(X-Value)] if value http-response del-map(map.lst) %[src] if ! value See also : "http-request", section 3.4 about userlists and section 7 about ACL usage. http-send-name-header [<header>] Add the server name to a request. Use the header string given by <header> May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes Arguments : <header> The header string to use to send the server name The "http-send-name-header" statement causes the name of the target server to be added to the headers of an HTTP request. The name is added with the header string proved. See also : "server" id <value> Set a persistent ID to a proxy. May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : none Set a persistent ID for the proxy. This ID must be unique and positive. An unused ID will automatically be assigned if unset. The first assigned value will be 1. This ID is currently only returned in statistics. ignore-persist { if | unless } <condition> Declare a condition to ignore persistence May be used in sections: defaults | frontend | listen | backend no | yes | yes | yes By default, when cookie persistence is enabled, every requests containing the cookie are unconditionally persistent (assuming the target server is up and running). The "ignore-persist" statement allows one to declare various ACL-based conditions which, when met, will cause a request to ignore persistence. This is sometimes useful to load balance requests for static files, which often don't require persistence. This can also be used to fully disable persistence for a specific User-Agent (for example, some web crawler bots). Combined with "appsession", it can also help reduce HAProxy memory usage, as the appsession table won't grow if persistence is ignored. The persistence is ignored when an "if" condition is met, or unless an "unless" condition is met. See also : "force-persist", "cookie", and section 7 about ACL usage. log global log <address> [len <length>] <facility> [<level> [<minlevel>]] no log Enable per-instance logging of events and traffic. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Prefix : no should be used when the logger list must be flushed. For example, if you don't want to inherit from the default logger list. This prefix does not allow arguments. Arguments : global should be used when the instance's logging parameters are the same as the global ones. This is the most common usage. "global" replaces <address>, <facility> and <level> with those of the log entries found in the "global" section. Only one "log global" statement may be used per instance, and this form takes no other parameter. <address> indicates where to send the logs. It takes the same format as for the "global" section's logs, and can be one of : - An IPv4 address optionally followed by a colon (':') and a UDP port. If no port is specified, 514 is used by default (the standard syslog port). - An IPv6 address followed by a colon (':') and optionally a UDP port. If no port is specified, 514 is used by default (the standard syslog port). - A filesystem path to a UNIX domain socket, keeping in mind considerations for chroot (be sure the path is accessible inside the chroot) and uid/gid (be sure the path is appropriately writeable). Any part of the address string may reference any number of environment variables by preceding their name with a dollar sign ('$') and optionally enclosing them with braces ('{}'), similarly to what is done in Bourne shell. <length> is an optional maximum line length. Log lines larger than this value will be truncated before being sent. The reason is that syslog servers act differently on log line length. All servers support the default value of 1024, but some servers simply drop larger lines while others do log them. If a server supports long lines, it may make sense to set this value here in order to avoid truncating long lines. Similarly, if a server drops long lines, it is preferable to truncate them before sending them. Accepted values are 80 to 65535 inclusive. The default value of 1024 is generally fine for all standard usages. Some specific cases of long captures or JSON-formated logs may require larger values. <facility> must be one of the 24 standard syslog facilities : kern user mail daemon auth syslog lpr news uucp cron auth2 ftp ntp audit alert cron2 local0 local1 local2 local3 local4 local5 local6 local7 <level> is optional and can be specified to filter outgoing messages. By default, all messages are sent. If a level is specified, only messages with a severity at least as important as this level will be sent. An optional minimum level can be specified. If it is set, logs emitted with a more severe level than this one will be capped to this level. This is used to avoid sending "emerg" messages on all terminals on some default syslog configurations. Eight levels are known : emerg alert crit err warning notice info debug It is important to keep in mind that it is the frontend which decides what to log from a connection, and that in case of content switching, the log entries from the backend will be ignored. Connections are logged at level "info". However, backend log declaration define how and where servers status changes will be logged. Level "notice" will be used to indicate a server going up, "warning" will be used for termination signals and definitive service termination, and "alert" will be used for when a server goes down. Note : According to RFC3164, messages are truncated to 1024 bytes before being emitted. Example : log global log 127.0.0.1:514 local0 notice # only send important events log 127.0.0.1:514 local0 notice notice # same but limit output level log ${LOCAL_SYSLOG}:514 local0 notice # send to local server log-format <string> Specifies the log format string to use for traffic logs May be used in sections: defaults | frontend | listen | backend yes | yes | yes | no This directive specifies the log format string that will be used for all logs resulting from traffic passing through the frontend using this line. If the directive is used in a defaults section, all subsequent frontends will use the same log format. Please see section 8.2.4 which covers the log format string in depth. max-keep-alive-queue <value> Set the maximum server queue size for maintaining keep-alive connections May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes HTTP keep-alive tries to reuse the same server connection whenever possible, but sometimes it can be counter-productive, for example if a server has a lot of connections while other ones are idle. This is especially true for static servers. The purpose of this setting is to set a threshold on the number of queued connections at which haproxy stops trying to reuse the same server and prefers to find another one. The default value, -1, means there is no limit. A value of zero means that keep-alive requests will never be queued. For very close servers which can be reached with a low latency and which are not sensible to breaking keep-alive, a low value is recommended (eg: local static server can use a value of 10 or less). For remote servers suffering from a high latency, higher values might be needed to cover for the latency and/or the cost of picking a different server. Note that this has no impact on responses which are maintained to the same server consecutively to a 401 response. They will still go to the same server even if they have to be queued. See also : "option http-server-close", "option prefer-last-server", server "maxconn" and cookie persistence. maxconn <conns> Fix the maximum number of concurrent connections on a frontend May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <conns> is the maximum number of concurrent connections the frontend will accept to serve. Excess connections will be queued by the system in the socket's listen queue and will be served once a connection closes. If the system supports it, it can be useful on big sites to raise this limit very high so that haproxy manages connection queues, instead of leaving the clients with unanswered connection attempts. This value should not exceed the global maxconn. Also, keep in mind that a connection contains two buffers of 8kB each, as well as some other data resulting in about 17 kB of RAM being consumed per established connection. That means that a medium system equipped with 1GB of RAM can withstand around 40000-50000 concurrent connections if properly tuned. Also, when <conns> is set to large values, it is possible that the servers are not sized to accept such loads, and for this reason it is generally wise to assign them some reasonable connection limits. By default, this value is set to 2000. See also : "server", global section's "maxconn", "fullconn" mode { tcp|http|health } Set the running mode or protocol of the instance May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : tcp The instance will work in pure TCP mode. A full-duplex connection will be established between clients and servers, and no layer 7 examination will be performed. This is the default mode. It should be used for SSL, SSH, SMTP, ... http The instance will work in HTTP mode. The client request will be analyzed in depth before connecting to any server. Any request which is not RFC-compliant will be rejected. Layer 7 filtering, processing and switching will be possible. This is the mode which brings HAProxy most of its value. health The instance will work in "health" mode. It will just reply "OK" to incoming connections and close the connection. Alternatively, If the "httpchk" option is set, "HTTP/1.0 200 OK" will be sent instead. Nothing will be logged in either case. This mode is used to reply to external components health checks. This mode is deprecated and should not be used anymore as it is possible to do the same and even better by combining TCP or HTTP modes with the "monitor" keyword. When doing content switching, it is mandatory that the frontend and the backend are in the same mode (generally HTTP), otherwise the configuration will be refused. Example : defaults http_instances mode http See also : "monitor", "monitor-net" monitor fail { if | unless } <condition> Add a condition to report a failure to a monitor HTTP request. May be used in sections : defaults | frontend | listen | backend no | yes | yes | no Arguments : if <cond> the monitor request will fail if the condition is satisfied, and will succeed otherwise. The condition should describe a combined test which must induce a failure if all conditions are met, for instance a low number of servers both in a backend and its backup. unless <cond> the monitor request will succeed only if the condition is satisfied, and will fail otherwise. Such a condition may be based on a test on the presence of a minimum number of active servers in a list of backends. This statement adds a condition which can force the response to a monitor request to report a failure. By default, when an external component queries the URI dedicated to monitoring, a 200 response is returned. When one of the conditions above is met, haproxy will return 503 instead of 200. This is very useful to report a site failure to an external component which may base routing advertisements between multiple sites on the availability reported by haproxy. In this case, one would rely on an ACL involving the "nbsrv" criterion. Note that "monitor fail" only works in HTTP mode. Both status messages may be tweaked using "errorfile" or "errorloc" if needed. Example: frontend www mode http acl site_dead nbsrv(dynamic) lt 2 acl site_dead nbsrv(static) lt 2 monitor-uri /site_alive monitor fail if site_dead See also : "monitor-net", "monitor-uri", "errorfile", "errorloc" monitor-net <source> Declare a source network which is limited to monitor requests May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <source> is the source IPv4 address or network which will only be able to get monitor responses to any request. It can be either an IPv4 address, a host name, or an address followed by a slash ('/') followed by a mask. In TCP mode, any connection coming from a source matching <source> will cause the connection to be immediately closed without any log. This allows another equipment to probe the port and verify that it is still listening, without forwarding the connection to a remote server. In HTTP mode, a connection coming from a source matching <source> will be accepted, the following response will be sent without waiting for a request, then the connection will be closed : "HTTP/1.0 200 OK". This is normally enough for any front-end HTTP probe to detect that the service is UP and running without forwarding the request to a backend server. Note that this response is sent in raw format, without any transformation. This is important as it means that it will not be SSL-encrypted on SSL listeners. Monitor requests are processed very early, just after tcp-request connection ACLs which are the only ones able to block them. These connections are short lived and never wait for any data from the client. They cannot be logged, and it is the intended purpose. They are only used to report HAProxy's health to an upper component, nothing more. Please note that "monitor fail" rules do not apply to connections intercepted by "monitor-net". Last, please note that only one "monitor-net" statement can be specified in a frontend. If more than one is found, only the last one will be considered. Example : # addresses .252 and .253 are just probing us. frontend www monitor-net 192.168.0.252/31 See also : "monitor fail", "monitor-uri" monitor-uri <uri> Intercept a URI used by external components' monitor requests May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <uri> is the exact URI which we want to intercept to return HAProxy's health status instead of forwarding the request. When an HTTP request referencing <uri> will be received on a frontend, HAProxy will not forward it nor log it, but instead will return either "HTTP/1.0 200 OK" or "HTTP/1.0 503 Service unavailable", depending on failure conditions defined with "monitor fail". This is normally enough for any front-end HTTP probe to detect that the service is UP and running without forwarding the request to a backend server. Note that the HTTP method, the version and all headers are ignored, but the request must at least be valid at the HTTP level. This keyword may only be used with an HTTP-mode frontend. Monitor requests are processed very early. It is not possible to block nor divert them using ACLs. They cannot be logged either, and it is the intended purpose. They are only used to report HAProxy's health to an upper component, nothing more. However, it is possible to add any number of conditions using "monitor fail" and ACLs so that the result can be adjusted to whatever check can be imagined (most often the number of available servers in a backend). Example : # Use /haproxy_test to report haproxy's status frontend www mode http monitor-uri /haproxy_test See also : "monitor fail", "monitor-net" option abortonclose no option abortonclose Enable or disable early dropping of aborted requests pending in queues. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none In presence of very high loads, the servers will take some time to respond. The per-instance connection queue will inflate, and the response time will increase respective to the size of the queue times the average per-session response time. When clients will wait for more than a few seconds, they will often hit the "STOP" button on their browser, leaving a useless request in the queue, and slowing down other users, and the servers as well, because the request will eventually be served, then aborted at the first error encountered while delivering the response. As there is no way to distinguish between a full STOP and a simple output close on the client side, HTTP agents should be conservative and consider that the client might only have closed its output channel while waiting for the response. However, this introduces risks of congestion when lots of users do the same, and is completely useless nowadays because probably no client at all will close the session while waiting for the response. Some HTTP agents support this behaviour (Squid, Apache, HAProxy), and others do not (TUX, most hardware-based load balancers). So the probability for a closed input channel to represent a user hitting the "STOP" button is close to 100%, and the risk of being the single component to break rare but valid traffic is extremely low, which adds to the temptation to be able to abort a session early while still not served and not pollute the servers. In HAProxy, the user can choose the desired behaviour using the option "abortonclose". By default (without the option) the behaviour is HTTP compliant and aborted requests will be served. But when the option is specified, a session with an incoming channel closed will be aborted while it is still possible, either pending in the queue for a connection slot, or during the connection establishment if the server has not yet acknowledged the connection request. This considerably reduces the queue size and the load on saturated servers when users are tempted to click on STOP, which in turn reduces the response time for other users. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "timeout queue" and server's "maxconn" and "maxqueue" parameters option accept-invalid-http-request no option accept-invalid-http-request Enable or disable relaxing of HTTP request parsing May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none By default, HAProxy complies with RFC7230 in terms of message parsing. This means that invalid characters in header names are not permitted and cause an error to be returned to the client. This is the desired behaviour as such forbidden characters are essentially used to build attacks exploiting server weaknesses, and bypass security filtering. Sometimes, a buggy browser or server will emit invalid header names for whatever reason (configuration, implementation) and the issue will not be immediately fixed. In such a case, it is possible to relax HAProxy's header name parser to accept any character even if that does not make sense, by specifying this option. Similarly, the list of characters allowed to appear in a URI is well defined by RFC3986, and chars 0-31, 32 (space), 34 ('"'), 60 ('<'), 62 ('>'), 92 ('\'), 94 ('^'), 96 ('`'), 123 ('{'), 124 ('|'), 125 ('}'), 127 (delete) and anything above are not allowed at all. Haproxy always blocks a number of them (0..32, 127). The remaining ones are blocked by default unless this option is enabled. This option also relaxes the test on the HTTP version format, it allows multiple digits for both the major and the minor version. This option should never be enabled by default as it hides application bugs and open security breaches. It should only be deployed after a problem has been confirmed. When this option is enabled, erroneous header names will still be accepted in requests, but the complete request will be captured in order to permit later analysis using the "show errors" request on the UNIX stats socket. Similarly, requests containing invalid chars in the URI part will be logged. Doing this also helps confirming that the issue has been solved. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option accept-invalid-http-response" and "show errors" on the stats socket. option accept-invalid-http-response no option accept-invalid-http-response Enable or disable relaxing of HTTP response parsing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none By default, HAProxy complies with RFC7230 in terms of message parsing. This means that invalid characters in header names are not permitted and cause an error to be returned to the client. This is the desired behaviour as such forbidden characters are essentially used to build attacks exploiting server weaknesses, and bypass security filtering. Sometimes, a buggy browser or server will emit invalid header names for whatever reason (configuration, implementation) and the issue will not be immediately fixed. In such a case, it is possible to relax HAProxy's header name parser to accept any character even if that does not make sense, by specifying this option. This option also relaxes the test on the HTTP version format, it allows multiple digits for both the major and the minor version. This option should never be enabled by default as it hides application bugs and open security breaches. It should only be deployed after a problem has been confirmed. When this option is enabled, erroneous header names will still be accepted in responses, but the complete response will be captured in order to permit later analysis using the "show errors" request on the UNIX stats socket. Doing this also helps confirming that the issue has been solved. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option accept-invalid-http-request" and "show errors" on the stats socket. option allbackups no option allbackups Use either all backup servers at a time or only the first one May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none By default, the first operational backup server gets all traffic when normal servers are all down. Sometimes, it may be preferred to use multiple backups at once, because one will not be enough. When "option allbackups" is enabled, the load balancing will be performed among all backup servers when all normal ones are unavailable. The same load balancing algorithm will be used and the servers' weights will be respected. Thus, there will not be any priority order between the backup servers anymore. This option is mostly used with static server farms dedicated to return a "sorry" page when an application is completely offline. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. option checkcache no option checkcache Analyze all server responses and block responses with cacheable cookies May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none Some high-level frameworks set application cookies everywhere and do not always let enough control to the developer to manage how the responses should be cached. When a session cookie is returned on a cacheable object, there is a high risk of session crossing or stealing between users traversing the same caches. In some situations, it is better to block the response than to let some sensitive session information go in the wild. The option "checkcache" enables deep inspection of all server responses for strict compliance with HTTP specification in terms of cacheability. It carefully checks "Cache-control", "Pragma" and "Set-cookie" headers in server response to check if there's a risk of caching a cookie on a client-side proxy. When this option is enabled, the only responses which can be delivered to the client are : - all those without "Set-Cookie" header ; - all those with a return code other than 200, 203, 206, 300, 301, 410, provided that the server has not set a "Cache-control: public" header ; - all those that come from a POST request, provided that the server has not set a 'Cache-Control: public' header ; - those with a 'Pragma: no-cache' header - those with a 'Cache-control: private' header - those with a 'Cache-control: no-store' header - those with a 'Cache-control: max-age=0' header - those with a 'Cache-control: s-maxage=0' header - those with a 'Cache-control: no-cache' header - those with a 'Cache-control: no-cache="set-cookie"' header - those with a 'Cache-control: no-cache="set-cookie,' header (allowing other fields after set-cookie) If a response doesn't respect these requirements, then it will be blocked just as if it was from an "rspdeny" filter, with an "HTTP 502 bad gateway". The session state shows "PH--" meaning that the proxy blocked the response during headers processing. Additionally, an alert will be sent in the logs so that admins are informed that there's something to be fixed. Due to the high impact on the application, the application should be tested in depth with the option enabled before going to production. It is also a good practice to always activate it during tests, even if it is not used in production, as it will report potentially dangerous application behaviours. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. option clitcpka no option clitcpka Enable or disable the sending of TCP keepalive packets on the client side May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none When there is a firewall or any session-aware component between a client and a server, and when the protocol involves very long sessions with long idle periods (eg: remote desktops), there is a risk that one of the intermediate components decides to expire a session which has remained idle for too long. Enabling socket-level TCP keep-alives makes the system regularly send packets to the other end of the connection, leaving it active. The delay between keep-alive probes is controlled by the system only and depends both on the operating system and its tuning parameters. It is important to understand that keep-alive packets are neither emitted nor received at the application level. It is only the network stacks which sees them. For this reason, even if one side of the proxy already uses keep-alives to maintain its connection alive, those keep-alive packets will not be forwarded to the other side of the proxy. Please note that this has nothing to do with HTTP keep-alive. Using option "clitcpka" enables the emission of TCP keep-alive probes on the client side of a connection, which should help when session expirations are noticed between HAProxy and a client. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option srvtcpka", "option tcpka" option contstats Enable continuous traffic statistics updates May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none By default, counters used for statistics calculation are incremented only when a session finishes. It works quite well when serving small objects, but with big ones (for example large images or archives) or with A/V streaming, a graph generated from haproxy counters looks like a hedgehog. With this option enabled counters get incremented continuously, during a whole session. Recounting touches a hotpath directly so it is not enabled by default, as it has small performance impact (~0.5%). option dontlog-normal no option dontlog-normal Enable or disable logging of normal, successful connections May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none There are large sites dealing with several thousand connections per second and for which logging is a major pain. Some of them are even forced to turn logs off and cannot debug production issues. Setting this option ensures that normal connections, those which experience no error, no timeout, no retry nor redispatch, will not be logged. This leaves disk space for anomalies. In HTTP mode, the response status code is checked and return codes 5xx will still be logged. It is strongly discouraged to use this option as most of the time, the key to complex issues is in the normal logs which will not be logged here. If you need to separate logs, see the "log-separate-errors" option instead. See also : "log", "dontlognull", "log-separate-errors" and section 8 about logging. option dontlognull no option dontlognull Enable or disable logging of null connections May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none In certain environments, there are components which will regularly connect to various systems to ensure that they are still alive. It can be the case from another load balancer as well as from monitoring systems. By default, even a simple port probe or scan will produce a log. If those connections pollute the logs too much, it is possible to enable option "dontlognull" to indicate that a connection on which no data has been transferred will not be logged, which typically corresponds to those probes. Note that errors will still be returned to the client and accounted for in the stats. If this is not what is desired, option http-ignore-probes can be used instead. It is generally recommended not to use this option in uncontrolled environments (eg: internet), otherwise scans and other malicious activities would not be logged. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "log", "http-ignore-probes", "monitor-net", "monitor-uri", and section 8 about logging. option forceclose no option forceclose Enable or disable active connection closing after response is transferred. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none Some HTTP servers do not necessarily close the connections when they receive the "Connection: close" set by "option httpclose", and if the client does not close either, then the connection remains open till the timeout expires. This causes high number of simultaneous connections on the servers and shows high global session times in the logs. When this happens, it is possible to use "option forceclose". It will actively close the outgoing server channel as soon as the server has finished to respond and release some resources earlier than with "option httpclose". This option may also be combined with "option http-pretend-keepalive", which will disable sending of the "Connection: close" header, but will still cause the connection to be closed once the whole response is received. This option disables and replaces any previous "option httpclose", "option http-server-close", "option http-keep-alive", or "option http-tunnel". If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option httpclose" and "option http-pretend-keepalive" option forwardfor [ except <network> ] [ header <name> ] [ if-none ] Enable insertion of the X-Forwarded-For header to requests sent to servers May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <network> is an optional argument used to disable this option for sources matching <network> <name> an optional argument to specify a different "X-Forwarded-For" header name. Since HAProxy works in reverse-proxy mode, the servers see its IP address as their client address. This is sometimes annoying when the client's IP address is expected in server logs. To solve this problem, the well-known HTTP header "X-Forwarded-For" may be added by HAProxy to all requests sent to the server. This header contains a value representing the client's IP address. Since this header is always appended at the end of the existing header list, the server must be configured to always use the last occurrence of this header only. See the server's manual to find how to enable use of this standard header. Note that only the last occurrence of the header must be used, since it is really possible that the client has already brought one. The keyword "header" may be used to supply a different header name to replace the default "X-Forwarded-For". This can be useful where you might already have a "X-Forwarded-For" header from a different application (eg: stunnel), and you need preserve it. Also if your backend server doesn't use the "X-Forwarded-For" header and requires different one (eg: Zeus Web Servers require "X-Cluster-Client-IP"). Sometimes, a same HAProxy instance may be shared between a direct client access and a reverse-proxy access (for instance when an SSL reverse-proxy is used to decrypt HTTPS traffic). It is possible to disable the addition of the header for a known source address or network by adding the "except" keyword followed by the network address. In this case, any source IP matching the network will not cause an addition of this header. Most common uses are with private networks or 127.0.0.1. Alternatively, the keyword "if-none" states that the header will only be added if it is not present. This should only be used in perfectly trusted environment, as this might cause a security issue if headers reaching haproxy are under the control of the end-user. This option may be specified either in the frontend or in the backend. If at least one of them uses it, the header will be added. Note that the backend's setting of the header subargument takes precedence over the frontend's if both are defined. In the case of the "if-none" argument, if at least one of the frontend or the backend does not specify it, it wants the addition to be mandatory, so it wins. Examples : # Public HTTP address also used by stunnel on the same machine frontend www mode http option forwardfor except 127.0.0.1 # stunnel already adds the header # Those servers want the IP Address in X-Client backend www mode http option forwardfor header X-Client See also : "option httpclose", "option http-server-close", "option forceclose", "option http-keep-alive" option http-ignore-probes no option http-ignore-probes Enable or disable logging of null connections and request timeouts May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none Recently some browsers started to implement a "pre-connect" feature consisting in speculatively connecting to some recently visited web sites just in case the user would like to visit them. This results in many connections being established to web sites, which end up in 408 Request Timeout if the timeout strikes first, or 400 Bad Request when the browser decides to close them first. These ones pollute the log and feed the error counters. There was already "option dontlognull" but it's insufficient in this case. Instead, this option does the following things : - prevent any 400/408 message from being sent to the client if nothing was received over a connection before it was closed ; - prevent any log from being emitted in this situation ; - prevent any error counter from being incremented That way the empty connection is silently ignored. Note that it is better not to use this unless it is clear that it is needed, because it will hide real problems. The most common reason for not receiving a request and seeing a 408 is due to an MTU inconsistency between the client and an intermediary element such as a VPN, which blocks too large packets. These issues are generally seen with POST requests as well as GET with large cookies. The logs are often the only way to detect them. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "log", "dontlognull", "errorfile", and section 8 about logging. option http-keep-alive no option http-keep-alive Enable or disable HTTP keep-alive from client to server May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none By default HAProxy operates in keep-alive mode with regards to persistent connections: for each connection it processes each request and response, and leaves the connection idle on both sides between the end of a response and the start of a new request. This mode may be changed by several options such as "option http-server-close", "option forceclose", "option httpclose" or "option http-tunnel". This option allows to set back the keep-alive mode, which can be useful when another mode was used in a defaults section. Setting "option http-keep-alive" enables HTTP keep-alive mode on the client- and server- sides. This provides the lowest latency on the client side (slow network) and the fastest session reuse on the server side at the expense of maintaining idle connections to the servers. In general, it is possible with this option to achieve approximately twice the request rate that the "http-server-close" option achieves on small objects. There are mainly two situations where this option may be useful : - when the server is non-HTTP compliant and authenticates the connection instead of requests (eg: NTLM authentication) - when the cost of establishing the connection to the server is significant compared to the cost of retrieving the associated object from the server. This last case can happen when the server is a fast static server of cache. In this case, the server will need to be properly tuned to support high enough connection counts because connections will last until the client sends another request. If the client request has to go to another backend or another server due to content switching or the load balancing algorithm, the idle connection will immediately be closed and a new one re-opened. Option "prefer-last-server" is available to try optimize server selection so that if the server currently attached to an idle connection is usable, it will be used. In general it is preferred to use "option http-server-close" with application servers, and some static servers might benefit from "option http-keep-alive". At the moment, logs will not indicate whether requests came from the same session or not. The accept date reported in the logs corresponds to the end of the previous request, and the request time corresponds to the time spent waiting for a new request. The keep-alive request time is still bound to the timeout defined by "timeout http-keep-alive" or "timeout http-request" if not set. This option disables and replaces any previous "option httpclose", "option http-server-close", "option forceclose" or "option http-tunnel". When backend and frontend options differ, all of these 4 options have precedence over "option http-keep-alive". See also : "option forceclose", "option http-server-close", "option prefer-last-server", "option http-pretend-keepalive", "option httpclose", and "1.1. The HTTP transaction model". option http-no-delay no option http-no-delay Instruct the system to favor low interactive delays over performance in HTTP May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none In HTTP, each payload is unidirectional and has no notion of interactivity. Any agent is expected to queue data somewhat for a reasonably low delay. There are some very rare server-to-server applications that abuse the HTTP protocol and expect the payload phase to be highly interactive, with many interleaved data chunks in both directions within a single request. This is absolutely not supported by the HTTP specification and will not work across most proxies or servers. When such applications attempt to do this through haproxy, it works but they will experience high delays due to the network optimizations which favor performance by instructing the system to wait for enough data to be available in order to only send full packets. Typical delays are around 200 ms per round trip. Note that this only happens with abnormal uses. Normal uses such as CONNECT requests nor WebSockets are not affected. When "option http-no-delay" is present in either the frontend or the backend used by a connection, all such optimizations will be disabled in order to make the exchanges as fast as possible. Of course this offers no guarantee on the functionality, as it may break at any other place. But if it works via HAProxy, it will work as fast as possible. This option should never be used by default, and should never be used at all unless such a buggy application is discovered. The impact of using this option is an increase of bandwidth usage and CPU usage, which may significantly lower performance in high latency environments. option http-pretend-keepalive no option http-pretend-keepalive Define whether haproxy will announce keepalive to the server or not May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none When running with "option http-server-close" or "option forceclose", haproxy adds a "Connection: close" header to the request forwarded to the server. Unfortunately, when some servers see this header, they automatically refrain from using the chunked encoding for responses of unknown length, while this is totally unrelated. The immediate effect is that this prevents haproxy from maintaining the client connection alive. A second effect is that a client or a cache could receive an incomplete response without being aware of it, and consider the response complete. By setting "option http-pretend-keepalive", haproxy will make the server believe it will keep the connection alive. The server will then not fall back to the abnormal undesired above. When haproxy gets the whole response, it will close the connection with the server just as it would do with the "forceclose" option. That way the client gets a normal response and the connection is correctly closed on the server side. It is recommended not to enable this option by default, because most servers will more efficiently close the connection themselves after the last packet, and release its buffers slightly earlier. Also, the added packet on the network could slightly reduce the overall peak performance. However it is worth noting that when this option is enabled, haproxy will have slightly less work to do. So if haproxy is the bottleneck on the whole architecture, enabling this option might save a few CPU cycles. This option may be set both in a frontend and in a backend. It is enabled if at least one of the frontend or backend holding a connection has it enabled. This option may be combined with "option httpclose", which will cause keepalive to be announced to the server and close to be announced to the client. This practice is discouraged though. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option forceclose", "option http-server-close", and "option http-keep-alive" option http-server-close no option http-server-close Enable or disable HTTP connection closing on the server side May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none By default HAProxy operates in keep-alive mode with regards to persistent connections: for each connection it processes each request and response, and leaves the connection idle on both sides between the end of a response and the start of a new request. This mode may be changed by several options such as "option http-server-close", "option forceclose", "option httpclose" or "option http-tunnel". Setting "option http-server-close" enables HTTP connection-close mode on the server side while keeping the ability to support HTTP keep-alive and pipelining on the client side. This provides the lowest latency on the client side (slow network) and the fastest session reuse on the server side to save server resources, similarly to "option forceclose". It also permits non-keepalive capable servers to be served in keep-alive mode to the clients if they conform to the requirements of RFC2616. Please note that some servers do not always conform to those requirements when they see "Connection: close" in the request. The effect will be that keep-alive will never be used. A workaround consists in enabling "option http-pretend-keepalive". At the moment, logs will not indicate whether requests came from the same session or not. The accept date reported in the logs corresponds to the end of the previous request, and the request time corresponds to the time spent waiting for a new request. The keep-alive request time is still bound to the timeout defined by "timeout http-keep-alive" or "timeout http-request" if not set. This option may be set both in a frontend and in a backend. It is enabled if at least one of the frontend or backend holding a connection has it enabled. It disables and replaces any previous "option httpclose", "option forceclose", "option http-tunnel" or "option http-keep-alive". Please check section 4 ("Proxies") to see how this option combines with others when frontend and backend options differ. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option forceclose", "option http-pretend-keepalive", "option httpclose", "option http-keep-alive", and "1.1. The HTTP transaction model". option http-tunnel no option http-tunnel Disable or enable HTTP connection processing after first transaction May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none By default HAProxy operates in keep-alive mode with regards to persistent connections: for each connection it processes each request and response, and leaves the connection idle on both sides between the end of a response and the start of a new request. This mode may be changed by several options such as "option http-server-close", "option forceclose", "option httpclose" or "option http-tunnel". Option "http-tunnel" disables any HTTP processing past the first request and the first response. This is the mode which was used by default in versions 1.0 to 1.5-dev21. It is the mode with the lowest processing overhead, which is normally not needed anymore unless in very specific cases such as when using an in-house protocol that looks like HTTP but is not compatible, or just to log one request per client in order to reduce log size. Note that everything which works at the HTTP level, including header parsing/addition, cookie processing or content switching will only work for the first request and will be ignored after the first response. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option forceclose", "option http-server-close", "option httpclose", "option http-keep-alive", and "1.1. The HTTP transaction model". option http-use-proxy-header no option http-use-proxy-header Make use of non-standard Proxy-Connection header instead of Connection May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none While RFC2616 explicitly states that HTTP/1.1 agents must use the Connection header to indicate their wish of persistent or non-persistent connections, both browsers and proxies ignore this header for proxied connections and make use of the undocumented, non-standard Proxy-Connection header instead. The issue begins when trying to put a load balancer between browsers and such proxies, because there will be a difference between what haproxy understands and what the client and the proxy agree on. By setting this option in a frontend, haproxy can automatically switch to use that non-standard header if it sees proxied requests. A proxied request is defined here as one where the URI begins with neither a '/' nor a '*'. The choice of header only affects requests passing through proxies making use of one of the "httpclose", "forceclose" and "http-server-close" options. Note that this option can only be specified in a frontend and will affect the request along its whole life. Also, when this option is set, a request which requires authentication will automatically switch to use proxy authentication headers if it is itself a proxied request. That makes it possible to check or enforce authentication in front of an existing proxy. This option should normally never be used, except in front of a proxy. See also : "option httpclose", "option forceclose" and "option http-server-close". option httpchk option httpchk <uri> option httpchk <method> <uri> option httpchk <method> <uri> <version> Enable HTTP protocol to check on the servers health May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <method> is the optional HTTP method used with the requests. When not set, the "OPTIONS" method is used, as it generally requires low server processing and is easy to filter out from the logs. Any method may be used, though it is not recommended to invent non-standard ones. <uri> is the URI referenced in the HTTP requests. It defaults to " / " which is accessible by default on almost any server, but may be changed to any other URI. Query strings are permitted. <version> is the optional HTTP version string. It defaults to "HTTP/1.0" but some servers might behave incorrectly in HTTP 1.0, so turning it to HTTP/1.1 may sometimes help. Note that the Host field is mandatory in HTTP/1.1, and as a trick, it is possible to pass it after "\r\n" following the version string. By default, server health checks only consist in trying to establish a TCP connection. When "option httpchk" is specified, a complete HTTP request is sent once the TCP connection is established, and responses 2xx and 3xx are considered valid, while all other ones indicate a server failure, including the lack of any response. The port and interval are specified in the server configuration. This option does not necessarily require an HTTP backend, it also works with plain TCP backends. This is particularly useful to check simple scripts bound to some dedicated ports using the inetd daemon. Examples : # Relay HTTPS traffic to Apache instance and check service availability # using HTTP request "OPTIONS * HTTP/1.1" on port 80. backend https_relay mode tcp option httpchk OPTIONS * HTTP/1.1\r\nHost:\ www server apache1 192.168.1.1:443 check port 80 See also : "option ssl-hello-chk", "option smtpchk", "option mysql-check", "option pgsql-check", "http-check" and the "check", "port" and "inter" server options. option httpclose no option httpclose Enable or disable passive HTTP connection closing May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none By default HAProxy operates in keep-alive mode with regards to persistent connections: for each connection it processes each request and response, and leaves the connection idle on both sides between the end of a response and the start of a new request. This mode may be changed by several options such as "option http-server-close", "option forceclose", "option httpclose" or "option http-tunnel". If "option httpclose" is set, HAProxy will work in HTTP tunnel mode and check if a "Connection: close" header is already set in each direction, and will add one if missing. Each end should react to this by actively closing the TCP connection after each transfer, thus resulting in a switch to the HTTP close mode. Any "Connection" header different from "close" will also be removed. Note that this option is deprecated since what it does is very cheap but not reliable. Using "option http-server-close" or "option forceclose" is strongly recommended instead. It seldom happens that some servers incorrectly ignore this header and do not close the connection even though they reply "Connection: close". For this reason, they are not compatible with older HTTP 1.0 browsers. If this happens it is possible to use the "option forceclose" which actively closes the request connection once the server responds. Option "forceclose" also releases the server connection earlier because it does not have to wait for the client to acknowledge it. This option may be set both in a frontend and in a backend. It is enabled if at least one of the frontend or backend holding a connection has it enabled. It disables and replaces any previous "option http-server-close", "option forceclose", "option http-keep-alive" or "option http-tunnel". Please check section 4 ("Proxies") to see how this option combines with others when frontend and backend options differ. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option forceclose", "option http-server-close" and "1.1. The HTTP transaction model". option httplog [ clf ] Enable logging of HTTP request, session state and timers May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : clf if the "clf" argument is added, then the output format will be the CLF format instead of HAProxy's default HTTP format. You can use this when you need to feed HAProxy's logs through a specific log analyser which only support the CLF format and which is not extensible. By default, the log output format is very poor, as it only contains the source and destination addresses, and the instance name. By specifying "option httplog", each log line turns into a much richer format including, but not limited to, the HTTP request, the connection timers, the session status, the connections numbers, the captured headers and cookies, the frontend, backend and server name, and of course the source address and ports. This option may be set either in the frontend or the backend. Specifying only "option httplog" will automatically clear the 'clf' mode if it was set by default. See also : section 8 about logging. option http_proxy no option http_proxy Enable or disable plain HTTP proxy mode May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none It sometimes happens that people need a pure HTTP proxy which understands basic proxy requests without caching nor any fancy feature. In this case, it may be worth setting up an HAProxy instance with the "option http_proxy" set. In this mode, no server is declared, and the connection is forwarded to the IP address and port found in the URL after the "http://" scheme. No host address resolution is performed, so this only works when pure IP addresses are passed. Since this option's usage perimeter is rather limited, it will probably be used only by experts who know they need exactly it. Last, if the clients are susceptible of sending keep-alive requests, it will be needed to add "option httpclose" to ensure that all requests will correctly be analyzed. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. Example : # this backend understands HTTP proxy requests and forwards them directly. backend direct_forward option httpclose option http_proxy See also : "option httpclose" option independent-streams no option independent-streams Enable or disable independent timeout processing for both directions May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none By default, when data is sent over a socket, both the write timeout and the read timeout for that socket are refreshed, because we consider that there is activity on that socket, and we have no other means of guessing if we should receive data or not. While this default behaviour is desirable for almost all applications, there exists a situation where it is desirable to disable it, and only refresh the read timeout if there are incoming data. This happens on sessions with large timeouts and low amounts of exchanged data such as telnet session. If the server suddenly disappears, the output data accumulates in the system's socket buffers, both timeouts are correctly refreshed, and there is no way to know the server does not receive them, so we don't timeout. However, when the underlying protocol always echoes sent data, it would be enough by itself to detect the issue using the read timeout. Note that this problem does not happen with more verbose protocols because data won't accumulate long in the socket buffers. When this option is set on the frontend, it will disable read timeout updates on data sent to the client. There probably is little use of this case. When the option is set on the backend, it will disable read timeout updates on data sent to the server. Doing so will typically break large HTTP posts from slow lines, so use it with caution. Note: older versions used to call this setting "option independent-streams" with a spelling mistake. This spelling is still supported but deprecated. See also : "timeout client", "timeout server" and "timeout tunnel" option ldap-check Use LDAPv3 health checks for server testing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none It is possible to test that the server correctly talks LDAPv3 instead of just testing that it accepts the TCP connection. When this option is set, an LDAPv3 anonymous simple bind message is sent to the server, and the response is analyzed to find an LDAPv3 bind response message. The server is considered valid only when the LDAP response contains success resultCode (http://tools.ietf.org/html/rfc4511#section-4.1.9). Logging of bind requests is server dependent see your documentation how to configure it. Example : option ldap-check See also : "option httpchk" option log-health-checks no option log-health-checks Enable or disable logging of health checks status updates May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none By default, failed health check are logged if server is UP and successful health checks are logged if server is DOWN, so the amount of additional information is limited. When this option is enabled, any change of the health check status or to the server's health will be logged, so that it becomes possible to know that a server was failing occasional checks before crashing, or exactly when it failed to respond a valid HTTP status, then when the port started to reject connections, then when the server stopped responding at all. Note that status changes not caused by health checks (eg: enable/disable on the CLI) are intentionally not logged by this option. See also: "option httpchk", "option ldap-check", "option mysql-check", "option pgsql-check", "option redis-check", "option smtpchk", "option tcp-check", "log" and section 8 about logging. option log-separate-errors no option log-separate-errors Change log level for non-completely successful connections May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none Sometimes looking for errors in logs is not easy. This option makes haproxy raise the level of logs containing potentially interesting information such as errors, timeouts, retries, redispatches, or HTTP status codes 5xx. The level changes from "info" to "err". This makes it possible to log them separately to a different file with most syslog daemons. Be careful not to remove them from the original file, otherwise you would lose ordering which provides very important information. Using this option, large sites dealing with several thousand connections per second may log normal traffic to a rotating buffer and only archive smaller error logs. See also : "log", "dontlognull", "dontlog-normal" and section 8 about logging. option logasap no option logasap Enable or disable early logging of HTTP requests May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none By default, HTTP requests are logged upon termination so that the total transfer time and the number of bytes appear in the logs. When large objects are being transferred, it may take a while before the request appears in the logs. Using "option logasap", the request gets logged as soon as the server sends the complete headers. The only missing information in the logs will be the total number of bytes which will indicate everything except the amount of data transferred, and the total time which will not take the transfer time into account. In such a situation, it's a good practice to capture the "Content-Length" response header so that the logs at least indicate how many bytes are expected to be transferred. Examples : listen http_proxy 0.0.0.0:80 mode http option httplog option logasap log 192.168.2.200 local3 >>> Feb 6 12:14:14 localhost \ haproxy[14389]: 10.0.1.2:33317 [06/Feb/2009:12:14:14.655] http-in \ static/srv1 9/10/7/14/+30 200 +243 - - ---- 3/1/1/1/0 1/0 \ "GET /image.iso HTTP/1.0" See also : "option httplog", "capture response header", and section 8 about logging. option mysql-check [ user <username> [ post-41 ] ] Use MySQL health checks for server testing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <username> This is the username which will be used when connecting to MySQL server. post-41 Send post v4.1 client compatible checks If you specify a username, the check consists of sending two MySQL packet, one Client Authentication packet, and one QUIT packet, to correctly close MySQL session. We then parse the MySQL Handshake Initialisation packet and/or Error packet. It is a basic but useful test which does not produce error nor aborted connect on the server. However, it requires adding an authorization in the MySQL table, like this : USE mysql; INSERT INTO user (Host,User) values ('<ip_of_haproxy>','<username>'); FLUSH PRIVILEGES; If you don't specify a username (it is deprecated and not recommended), the check only consists in parsing the Mysql Handshake Initialisation packet or Error packet, we don't send anything in this mode. It was reported that it can generate lockout if check is too frequent and/or if there is not enough traffic. In fact, you need in this case to check MySQL "max_connect_errors" value as if a connection is established successfully within fewer than MySQL "max_connect_errors" attempts after a previous connection was interrupted, the error count for the host is cleared to zero. If HAProxy's server get blocked, the "FLUSH HOSTS" statement is the only way to unblock it. Remember that this does not check database presence nor database consistency. To do this, you can use an external check with xinetd for example. The check requires MySQL >=3.22, for older version, please use TCP check. Most often, an incoming MySQL server needs to see the client's IP address for various purposes, including IP privilege matching and connection logging. When possible, it is often wise to masquerade the client's IP address when connecting to the server using the "usesrc" argument of the "source" keyword, which requires the cttproxy feature to be compiled in, and the MySQL server to route the client via the machine hosting haproxy. See also: "option httpchk" option nolinger no option nolinger Enable or disable immediate session resource cleaning after close May be used in sections: defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none When clients or servers abort connections in a dirty way (eg: they are physically disconnected), the session timeouts triggers and the session is closed. But it will remain in FIN_WAIT1 state for some time in the system, using some resources and possibly limiting the ability to establish newer connections. When this happens, it is possible to activate "option nolinger" which forces the system to immediately remove any socket's pending data on close. Thus, the session is instantly purged from the system's tables. This usually has side effects such as increased number of TCP resets due to old retransmits getting immediately rejected. Some firewalls may sometimes complain about this too. For this reason, it is not recommended to use this option when not absolutely needed. You know that you need it when you have thousands of FIN_WAIT1 sessions on your system (TIME_WAIT ones do not count). This option may be used both on frontends and backends, depending on the side where it is required. Use it on the frontend for clients, and on the backend for servers. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. option originalto [ except <network> ] [ header <name> ] Enable insertion of the X-Original-To header to requests sent to servers May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <network> is an optional argument used to disable this option for sources matching <network> <name> an optional argument to specify a different "X-Original-To" header name. Since HAProxy can work in transparent mode, every request from a client can be redirected to the proxy and HAProxy itself can proxy every request to a complex SQUID environment and the destination host from SO_ORIGINAL_DST will be lost. This is annoying when you want access rules based on destination ip addresses. To solve this problem, a new HTTP header "X-Original-To" may be added by HAProxy to all requests sent to the server. This header contains a value representing the original destination IP address. Since this must be configured to always use the last occurrence of this header only. Note that only the last occurrence of the header must be used, since it is really possible that the client has already brought one. The keyword "header" may be used to supply a different header name to replace the default "X-Original-To". This can be useful where you might already have a "X-Original-To" header from a different application, and you need preserve it. Also if your backend server doesn't use the "X-Original-To" header and requires different one. Sometimes, a same HAProxy instance may be shared between a direct client access and a reverse-proxy access (for instance when an SSL reverse-proxy is used to decrypt HTTPS traffic). It is possible to disable the addition of the header for a known source address or network by adding the "except" keyword followed by the network address. In this case, any source IP matching the network will not cause an addition of this header. Most common uses are with private networks or 127.0.0.1. This option may be specified either in the frontend or in the backend. If at least one of them uses it, the header will be added. Note that the backend's setting of the header subargument takes precedence over the frontend's if both are defined. Examples : # Original Destination address frontend www mode http option originalto except 127.0.0.1 # Those servers want the IP Address in X-Client-Dst backend www mode http option originalto header X-Client-Dst See also : "option httpclose", "option http-server-close", "option forceclose" option persist no option persist Enable or disable forced persistence on down servers May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes Arguments : none When an HTTP request reaches a backend with a cookie which references a dead server, by default it is redispatched to another server. It is possible to force the request to be sent to the dead server first using "option persist" if absolutely needed. A common use case is when servers are under extreme load and spend their time flapping. In this case, the users would still be directed to the server they opened the session on, in the hope they would be correctly served. It is recommended to use "option redispatch" in conjunction with this option so that in the event it would not be possible to connect to the server at all (server definitely dead), the client would finally be redirected to another valid server. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option redispatch", "retries", "force-persist" option pgsql-check [ user <username> ] Use PostgreSQL health checks for server testing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <username> This is the username which will be used when connecting to PostgreSQL server. The check sends a PostgreSQL StartupMessage and waits for either Authentication request or ErrorResponse message. It is a basic but useful test which does not produce error nor aborted connect on the server. This check is identical with the "mysql-check". See also: "option httpchk" option prefer-last-server no option prefer-last-server Allow multiple load balanced requests to remain on the same server May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes Arguments : none When the load balancing algorithm in use is not deterministic, and a previous request was sent to a server to which haproxy still holds a connection, it is sometimes desirable that subsequent requests on a same session go to the same server as much as possible. Note that this is different from persistence, as we only indicate a preference which haproxy tries to apply without any form of warranty. The real use is for keep-alive connections sent to servers. When this option is used, haproxy will try to reuse the same connection that is attached to the server instead of rebalancing to another server, causing a close of the connection. This can make sense for static file servers. It does not make much sense to use this in combination with hashing algorithms. Note, haproxy already automatically tries to stick to a server which sends a 401 or to a proxy which sends a 407 (authentication required). This is mandatory for use with the broken NTLM authentication challenge, and significantly helps in troubleshooting some faulty applications. Option prefer-last-server might be desirable in these environments as well, to avoid redistributing the traffic after every other response. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also: "option http-keep-alive" option redispatch no option redispatch Enable or disable session redistribution in case of connection failure May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes Arguments : none In HTTP mode, if a server designated by a cookie is down, clients may definitely stick to it because they cannot flush the cookie, so they will not be able to access the service anymore. Specifying "option redispatch" will allow the proxy to break their persistence and redistribute them to a working server. It also allows to retry last connection to another server in case of multiple connection failures. Of course, it requires having "retries" set to a nonzero value. This form is the preferred form, which replaces both the "redispatch" and "redisp" keywords. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "redispatch", "retries", "force-persist" option redis-check Use redis health checks for server testing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none It is possible to test that the server correctly talks REDIS protocol instead of just testing that it accepts the TCP connection. When this option is set, a PING redis command is sent to the server, and the response is analyzed to find the "+PONG" response message. Example : option redis-check See also : "option httpchk" option smtpchk option smtpchk <hello> <domain> Use SMTP health checks for server testing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <hello> is an optional argument. It is the "hello" command to use. It can be either "HELO" (for SMTP) or "EHLO" (for ESTMP). All other values will be turned into the default command ("HELO"). <domain> is the domain name to present to the server. It may only be specified (and is mandatory) if the hello command has been specified. By default, "localhost" is used. When "option smtpchk" is set, the health checks will consist in TCP connections followed by an SMTP command. By default, this command is "HELO localhost". The server's return code is analyzed and only return codes starting with a "2" will be considered as valid. All other responses, including a lack of response will constitute an error and will indicate a dead server. This test is meant to be used with SMTP servers or relays. Depending on the request, it is possible that some servers do not log each connection attempt, so you may want to experiment to improve the behaviour. Using telnet on port 25 is often easier than adjusting the configuration. Most often, an incoming SMTP server needs to see the client's IP address for various purposes, including spam filtering, anti-spoofing and logging. When possible, it is often wise to masquerade the client's IP address when connecting to the server using the "usesrc" argument of the "source" keyword, which requires the cttproxy feature to be compiled in. Example : option smtpchk HELO mydomain.org See also : "option httpchk", "source" option socket-stats no option socket-stats Enable or disable collecting &providing separate statistics for each socket. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none option splice-auto no option splice-auto Enable or disable automatic kernel acceleration on sockets in both directions May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none When this option is enabled either on a frontend or on a backend, haproxy will automatically evaluate the opportunity to use kernel tcp splicing to forward data between the client and the server, in either direction. Haproxy uses heuristics to estimate if kernel splicing might improve performance or not. Both directions are handled independently. Note that the heuristics used are not much aggressive in order to limit excessive use of splicing. This option requires splicing to be enabled at compile time, and may be globally disabled with the global option "nosplice". Since splice uses pipes, using it requires that there are enough spare pipes. Important note: kernel-based TCP splicing is a Linux-specific feature which first appeared in kernel 2.6.25. It offers kernel-based acceleration to transfer data between sockets without copying these data to user-space, thus providing noticeable performance gains and CPU cycles savings. Since many early implementations are buggy, corrupt data and/or are inefficient, this feature is not enabled by default, and it should be used with extreme care. While it is not possible to detect the correctness of an implementation, 2.6.29 is the first version offering a properly working implementation. In case of doubt, splicing may be globally disabled using the global "nosplice" keyword. Example : option splice-auto If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option splice-request", "option splice-response", and global options "nosplice" and "maxpipes" option splice-request no option splice-request Enable or disable automatic kernel acceleration on sockets for requests May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none When this option is enabled either on a frontend or on a backend, haproxy will use kernel tcp splicing whenever possible to forward data going from the client to the server. It might still use the recv/send scheme if there are no spare pipes left. This option requires splicing to be enabled at compile time, and may be globally disabled with the global option "nosplice". Since splice uses pipes, using it requires that there are enough spare pipes. Important note: see "option splice-auto" for usage limitations. Example : option splice-request If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option splice-auto", "option splice-response", and global options "nosplice" and "maxpipes" option splice-response no option splice-response Enable or disable automatic kernel acceleration on sockets for responses May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none When this option is enabled either on a frontend or on a backend, haproxy will use kernel tcp splicing whenever possible to forward data going from the server to the client. It might still use the recv/send scheme if there are no spare pipes left. This option requires splicing to be enabled at compile time, and may be globally disabled with the global option "nosplice". Since splice uses pipes, using it requires that there are enough spare pipes. Important note: see "option splice-auto" for usage limitations. Example : option splice-response If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option splice-auto", "option splice-request", and global options "nosplice" and "maxpipes" option srvtcpka no option srvtcpka Enable or disable the sending of TCP keepalive packets on the server side May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none When there is a firewall or any session-aware component between a client and a server, and when the protocol involves very long sessions with long idle periods (eg: remote desktops), there is a risk that one of the intermediate components decides to expire a session which has remained idle for too long. Enabling socket-level TCP keep-alives makes the system regularly send packets to the other end of the connection, leaving it active. The delay between keep-alive probes is controlled by the system only and depends both on the operating system and its tuning parameters. It is important to understand that keep-alive packets are neither emitted nor received at the application level. It is only the network stacks which sees them. For this reason, even if one side of the proxy already uses keep-alives to maintain its connection alive, those keep-alive packets will not be forwarded to the other side of the proxy. Please note that this has nothing to do with HTTP keep-alive. Using option "srvtcpka" enables the emission of TCP keep-alive probes on the server side of a connection, which should help when session expirations are noticed between HAProxy and a server. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option clitcpka", "option tcpka" option ssl-hello-chk Use SSLv3 client hello health checks for server testing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none When some SSL-based protocols are relayed in TCP mode through HAProxy, it is possible to test that the server correctly talks SSL instead of just testing that it accepts the TCP connection. When "option ssl-hello-chk" is set, pure SSLv3 client hello messages are sent once the connection is established to the server, and the response is analyzed to find an SSL server hello message. The server is considered valid only when the response contains this server hello message. All servers tested till there correctly reply to SSLv3 client hello messages, and most servers tested do not even log the requests containing only hello messages, which is appreciable. Note that this check works even when SSL support was not built into haproxy because it forges the SSL message. When SSL support is available, it is best to use native SSL health checks instead of this one. See also: "option httpchk", "check-ssl" option tcp-check Perform health checks using tcp-check send/expect sequences May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes This health check method is intended to be combined with "tcp-check" command lists in order to support send/expect types of health check sequences. TCP checks currently support 4 modes of operations : - no "tcp-check" directive : the health check only consists in a connection attempt, which remains the default mode. - "tcp-check send" or "tcp-check send-binary" only is mentioned : this is used to send a string along with a connection opening. With some protocols, it helps sending a "QUIT" message for example that prevents the server from logging a connection error for each health check. The check result will still be based on the ability to open the connection only. - "tcp-check expect" only is mentioned : this is used to test a banner. The connection is opened and haproxy waits for the server to present some contents which must validate some rules. The check result will be based on the matching between the contents and the rules. This is suited for POP, IMAP, SMTP, FTP, SSH, TELNET. - both "tcp-check send" and "tcp-check expect" are mentioned : this is used to test a hello-type protocol. Haproxy sends a message, the server responds and its response is analysed. the check result will be based on the matching between the response contents and the rules. This is often suited for protocols which require a binding or a request/response model. LDAP, MySQL, Redis and SSL are example of such protocols, though they already all have their dedicated checks with a deeper understanding of the respective protocols. In this mode, many questions may be sent and many answers may be analysed. Examples : # perform a POP check (analyse only server's banner) option tcp-check tcp-check expect string +OK\ POP3\ ready # perform an IMAP check (analyse only server's banner) option tcp-check tcp-check expect string *\ OK\ IMAP4\ ready # look for the redis master server after ensuring it speaks well # redis protocol, then it exits properly. # (send a command then analyse the response 3 times) option tcp-check tcp-check send PING\r\n tcp-check expect +PONG tcp-check send info\ replication\r\n tcp-check expect string role:master tcp-check send QUIT\r\n tcp-check expect string +OK forge a HTTP request, then analyse the response (send many headers before analyzing) option tcp-check tcp-check send HEAD\ /\ HTTP/1.1\r\n tcp-check send Host:\ www.mydomain.com\r\n tcp-check send User-Agent:\ HAProxy\ tcpcheck\r\n tcp-check send \r\n tcp-check expect rstring HTTP/1\..\ (2..|3..) See also : "tcp-check expect", "tcp-check send" option tcp-smart-accept no option tcp-smart-accept Enable or disable the saving of one ACK packet during the accept sequence May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : none When an HTTP connection request comes in, the system acknowledges it on behalf of HAProxy, then the client immediately sends its request, and the system acknowledges it too while it is notifying HAProxy about the new connection. HAProxy then reads the request and responds. This means that we have one TCP ACK sent by the system for nothing, because the request could very well be acknowledged by HAProxy when it sends its response. For this reason, in HTTP mode, HAProxy automatically asks the system to avoid sending this useless ACK on platforms which support it (currently at least Linux). It must not cause any problem, because the system will send it anyway after 40 ms if the response takes more time than expected to come. During complex network debugging sessions, it may be desirable to disable this optimization because delayed ACKs can make troubleshooting more complex when trying to identify where packets are delayed. It is then possible to fall back to normal behaviour by specifying "no option tcp-smart-accept". It is also possible to force it for non-HTTP proxies by simply specifying "option tcp-smart-accept". For instance, it can make sense with some services such as SMTP where the server speaks first. It is recommended to avoid forcing this option in a defaults section. In case of doubt, consider setting it back to automatic values by prepending the "default" keyword before it, or disabling it using the "no" keyword. See also : "option tcp-smart-connect" option tcp-smart-connect no option tcp-smart-connect Enable or disable the saving of one ACK packet during the connect sequence May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none On certain systems (at least Linux), HAProxy can ask the kernel not to immediately send an empty ACK upon a connection request, but to directly send the buffer request instead. This saves one packet on the network and thus boosts performance. It can also be useful for some servers, because they immediately get the request along with the incoming connection. This feature is enabled when "option tcp-smart-connect" is set in a backend. It is not enabled by default because it makes network troubleshooting more complex. It only makes sense to enable it with protocols where the client speaks first such as HTTP. In other situations, if there is no data to send in place of the ACK, a normal ACK is sent. If this option has been enabled in a "defaults" section, it can be disabled in a specific instance by prepending the "no" keyword before it. See also : "option tcp-smart-accept" option tcpka Enable or disable the sending of TCP keepalive packets on both sides May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none When there is a firewall or any session-aware component between a client and a server, and when the protocol involves very long sessions with long idle periods (eg: remote desktops), there is a risk that one of the intermediate components decides to expire a session which has remained idle for too long. Enabling socket-level TCP keep-alives makes the system regularly send packets to the other end of the connection, leaving it active. The delay between keep-alive probes is controlled by the system only and depends both on the operating system and its tuning parameters. It is important to understand that keep-alive packets are neither emitted nor received at the application level. It is only the network stacks which sees them. For this reason, even if one side of the proxy already uses keep-alives to maintain its connection alive, those keep-alive packets will not be forwarded to the other side of the proxy. Please note that this has nothing to do with HTTP keep-alive. Using option "tcpka" enables the emission of TCP keep-alive probes on both the client and server sides of a connection. Note that this is meaningful only in "defaults" or "listen" sections. If this option is used in a frontend, only the client side will get keep-alives, and if this option is used in a backend, only the server side will get keep-alives. For this reason, it is strongly recommended to explicitly use "option clitcpka" and "option srvtcpka" when the configuration is split between frontends and backends. See also : "option clitcpka", "option srvtcpka" option tcplog Enable advanced logging of TCP connections with session state and timers May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none By default, the log output format is very poor, as it only contains the source and destination addresses, and the instance name. By specifying "option tcplog", each log line turns into a much richer format including, but not limited to, the connection timers, the session status, the connections numbers, the frontend, backend and server name, and of course the source address and ports. This option is useful for pure TCP proxies in order to find which of the client or server disconnects or times out. For normal HTTP proxies, it's better to use "option httplog" which is even more complete. This option may be set either in the frontend or the backend. See also : "option httplog", and section 8 about logging. option transparent no option transparent Enable client-side transparent proxying May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none This option was introduced in order to provide layer 7 persistence to layer 3 load balancers. The idea is to use the OS's ability to redirect an incoming connection for a remote address to a local process (here HAProxy), and let this process know what address was initially requested. When this option is used, sessions without cookies will be forwarded to the original destination IP address of the incoming request (which should match that of another equipment), while requests with cookies will still be forwarded to the appropriate server. Note that contrary to a common belief, this option does NOT make HAProxy present the client's IP to the server when establishing the connection. See also: the "usesrc" argument of the "source" keyword, and the "transparent" option of the "bind" keyword. persist rdp-cookie persist rdp-cookie(<name>) Enable RDP cookie-based persistence May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <name> is the optional name of the RDP cookie to check. If omitted, the default cookie name "msts" will be used. There currently is no valid reason to change this name. This statement enables persistence based on an RDP cookie. The RDP cookie contains all information required to find the server in the list of known servers. So when this option is set in the backend, the request is analysed and if an RDP cookie is found, it is decoded. If it matches a known server which is still UP (or if "option persist" is set), then the connection is forwarded to this server. Note that this only makes sense in a TCP backend, but for this to work, the frontend must have waited long enough to ensure that an RDP cookie is present in the request buffer. This is the same requirement as with the "rdp-cookie" load-balancing method. Thus it is highly recommended to put all statements in a single "listen" section. Also, it is important to understand that the terminal server will emit this RDP cookie only if it is configured for "token redirection mode", which means that the "IP address redirection" option is disabled. Example : listen tse-farm bind :3389 # wait up to 5s for an RDP cookie in the request tcp-request inspect-delay 5s tcp-request content accept if RDP_COOKIE # apply RDP cookie persistence persist rdp-cookie # if server is unknown, let's balance on the same cookie. # alternatively, "balance leastconn" may be useful too. balance rdp-cookie server srv1 1.1.1.1:3389 server srv2 1.1.1.2:3389 See also : "balance rdp-cookie", "tcp-request", the "req_rdp_cookie" ACL and the rdp_cookie pattern fetch function. rate-limit sessions <rate> Set a limit on the number of new sessions accepted per second on a frontend May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <rate> The <rate> parameter is an integer designating the maximum number of new sessions per second to accept on the frontend. When the frontend reaches the specified number of new sessions per second, it stops accepting new connections until the rate drops below the limit again. During this time, the pending sessions will be kept in the socket's backlog (in system buffers) and haproxy will not even be aware that sessions are pending. When applying very low limit on a highly loaded service, it may make sense to increase the socket's backlog using the "backlog" keyword. This feature is particularly efficient at blocking connection-based attacks or service abuse on fragile servers. Since the session rate is measured every millisecond, it is extremely accurate. Also, the limit applies immediately, no delay is needed at all to detect the threshold. Example : limit the connection rate on SMTP to 10 per second max listen smtp mode tcp bind :25 rate-limit sessions 10 server 127.0.0.1:1025 Note : when the maximum rate is reached, the frontend's status is not changed but its sockets appear as "WAITING" in the statistics if the "socket-stats" option is enabled. See also : the "backlog" keyword and the "fe_sess_rate" ACL criterion. redirect location <loc> [code <code>] <option> [{if | unless} <condition>] redirect prefix <pfx> [code <code>] <option> [{if | unless} <condition>] redirect scheme <sch> [code <code>] <option> [{if | unless} <condition>] Return an HTTP redirection if/unless a condition is matched May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes If/unless the condition is matched, the HTTP request will lead to a redirect response. If no condition is specified, the redirect applies unconditionally. Arguments : <loc> With "redirect location", the exact value in <loc> is placed into the HTTP "Location" header. When used in an "http-request" rule, <loc> value follows the log-format rules and can include some dynamic values (see Custom Log Format in section 8.2.4). <pfx> With "redirect prefix", the "Location" header is built from the concatenation of <pfx> and the complete URI path, including the query string, unless the "drop-query" option is specified (see below). As a special case, if <pfx> equals exactly "/", then nothing is inserted before the original URI. It allows one to redirect to the same URL (for instance, to insert a cookie). When used in an "http-request" rule, <pfx> value follows the log-format rules and can include some dynamic values (see Custom Log Format in section 8.2.4). <sch> With "redirect scheme", then the "Location" header is built by concatenating <sch> with "://" then the first occurrence of the "Host" header, and then the URI path, including the query string unless the "drop-query" option is specified (see below). If no path is found or if the path is "*", then "/" is used instead. If no "Host" header is found, then an empty host component will be returned, which most recent browsers interpret as redirecting to the same host. This directive is mostly used to redirect HTTP to HTTPS. When used in an "http-request" rule, <sch> value follows the log-format rules and can include some dynamic values (see Custom Log Format in section 8.2.4). <code> The code is optional. It indicates which type of HTTP redirection is desired. Only codes 301, 302, 303, 307 and 308 are supported, with 302 used by default if no code is specified. 301 means "Moved permanently", and a browser may cache the Location. 302 means "Moved permanently" and means that the browser should not cache the redirection. 303 is equivalent to 302 except that the browser will fetch the location with a GET method. 307 is just like 302 but makes it clear that the same method must be reused. Likewise, 308 replaces 301 if the same method must be used. <option> There are several options which can be specified to adjust the expected behaviour of a redirection : - "drop-query" When this keyword is used in a prefix-based redirection, then the location will be set without any possible query-string, which is useful for directing users to a non-secure page for instance. It has no effect with a location-type redirect. - "append-slash" This keyword may be used in conjunction with "drop-query" to redirect users who use a URL not ending with a '/' to the same one with the '/'. It can be useful to ensure that search engines will only see one URL. For this, a return code 301 is preferred. - "set-cookie NAME[=value]" A "Set-Cookie" header will be added with NAME (and optionally "=value") to the response. This is sometimes used to indicate that a user has been seen, for instance to protect against some types of DoS. No other cookie option is added, so the cookie will be a session cookie. Note that for a browser, a sole cookie name without an equal sign is different from a cookie with an equal sign. - "clear-cookie NAME[=]" A "Set-Cookie" header will be added with NAME (and optionally "="), but with the "Max-Age" attribute set to zero. This will tell the browser to delete this cookie. It is useful for instance on logout pages. It is important to note that clearing the cookie "NAME" will not remove a cookie set with "NAME=value". You have to clear the cookie "NAME=" for that, because the browser makes the difference. Example: move the login URL only to HTTPS. acl clear dst_port 80 acl secure dst_port 8080 acl login_page url_beg /login acl logout url_beg /logout acl uid_given url_reg /login?userid=[^&]+ acl cookie_set hdr_sub(cookie) SEEN=1 redirect prefix https://mysite.com set-cookie SEEN=1 if !cookie_set redirect prefix https://mysite.com if login_page !secure redirect prefix http://mysite.com drop-query if login_page !uid_given redirect location http://mysite.com/ if !login_page secure redirect location / clear-cookie USERID= if logout Example: send redirects for request for articles without a '/'. acl missing_slash path_reg ^/article/[^/]*$ redirect code 301 prefix / drop-query append-slash if missing_slash Example: redirect all HTTP traffic to HTTPS when SSL is handled by haproxy. redirect scheme https if !{ ssl_fc } Example: append 'www.' prefix in front of all hosts not having it http-request redirect code 301 location www.%[hdr(host)]%[req.uri] \ unless { hdr_beg(host) -i www } See section 7 about ACL usage. redisp (deprecated) redispatch (deprecated) Enable or disable session redistribution in case of connection failure May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes Arguments : none In HTTP mode, if a server designated by a cookie is down, clients may definitely stick to it because they cannot flush the cookie, so they will not be able to access the service anymore. Specifying "redispatch" will allow the proxy to break their persistence and redistribute them to a working server. It also allows to retry last connection to another server in case of multiple connection failures. Of course, it requires having "retries" set to a nonzero value. This form is deprecated, do not use it in any new configuration, use the new "option redispatch" instead. See also : "option redispatch" reqadd <string> [{if | unless} <cond>] Add a header at the end of the HTTP request May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <string> is the complete line to be added. Any space or known delimiter must be escaped using a backslash ('\'). Please refer to section 6 about HTTP header manipulation for more information. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. A new line consisting in <string> followed by a line feed will be added after the last header of an HTTP request. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Example : add "X-Proto: SSL" to requests coming via port 81 acl is-ssl dst_port 81 reqadd X-Proto:\ SSL if is-ssl See also: "rspadd", section 6 about HTTP header manipulation, and section 7 about ACLs. reqallow <search> [{if | unless} <cond>] reqiallow <search> [{if | unless} <cond>] (ignore case) Definitely allow an HTTP request if a line matches a regular expression May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the request line. This is an extended regular expression. Parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "reqallow" keyword strictly matches case while "reqiallow" ignores case. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. A request containing any line which matches extended regular expression <search> will mark the request as allowed, even if any later test would result in a deny. The test applies both to the request line and to request headers. Keep in mind that URLs in request line are case-sensitive while header names are not. It is easier, faster and more powerful to use ACLs to write access policies. Reqdeny, reqallow and reqpass should be avoided in new designs. Example : # allow www.* but refuse *.local reqiallow ^Host:\ www\. reqideny ^Host:\ .*\.local See also: "reqdeny", "block", section 6 about HTTP header manipulation, and section 7 about ACLs. reqdel <search> [{if | unless} <cond>] reqidel <search> [{if | unless} <cond>] (ignore case) Delete all headers matching a regular expression in an HTTP request May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the request line. This is an extended regular expression. Parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "reqdel" keyword strictly matches case while "reqidel" ignores case. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. Any header line matching extended regular expression <search> in the request will be completely deleted. Most common use of this is to remove unwanted and/or dangerous headers or cookies from a request before passing it to the next servers. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Keep in mind that header names are not case-sensitive. Example : # remove X-Forwarded-For header and SERVER cookie reqidel ^X-Forwarded-For:.* reqidel ^Cookie:.*SERVER= See also: "reqadd", "reqrep", "rspdel", section 6 about HTTP header manipulation, and section 7 about ACLs. reqdeny <search> [{if | unless} <cond>] reqideny <search> [{if | unless} <cond>] (ignore case) Deny an HTTP request if a line matches a regular expression May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the request line. This is an extended regular expression. Parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "reqdeny" keyword strictly matches case while "reqideny" ignores case. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. A request containing any line which matches extended regular expression <search> will mark the request as denied, even if any later test would result in an allow. The test applies both to the request line and to request headers. Keep in mind that URLs in request line are case-sensitive while header names are not. A denied request will generate an "HTTP 403 forbidden" response once the complete request has been parsed. This is consistent with what is practiced using ACLs. It is easier, faster and more powerful to use ACLs to write access policies. Reqdeny, reqallow and reqpass should be avoided in new designs. Example : # refuse *.local, then allow www.* reqideny ^Host:\ .*\.local reqiallow ^Host:\ www\. See also: "reqallow", "rspdeny", "block", section 6 about HTTP header manipulation, and section 7 about ACLs. reqpass <search> [{if | unless} <cond>] reqipass <search> [{if | unless} <cond>] (ignore case) Ignore any HTTP request line matching a regular expression in next rules May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the request line. This is an extended regular expression. Parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "reqpass" keyword strictly matches case while "reqipass" ignores case. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. A request containing any line which matches extended regular expression <search> will skip next rules, without assigning any deny or allow verdict. The test applies both to the request line and to request headers. Keep in mind that URLs in request line are case-sensitive while header names are not. It is easier, faster and more powerful to use ACLs to write access policies. Reqdeny, reqallow and reqpass should be avoided in new designs. Example : # refuse *.local, then allow www.*, but ignore "www.private.local" reqipass ^Host:\ www.private\.local reqideny ^Host:\ .*\.local reqiallow ^Host:\ www\. See also: "reqallow", "reqdeny", "block", section 6 about HTTP header manipulation, and section 7 about ACLs. reqrep <search> <string> [{if | unless} <cond>] reqirep <search> <string> [{if | unless} <cond>] (ignore case) Replace a regular expression with a string in an HTTP request line May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the request line. This is an extended regular expression. Parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "reqrep" keyword strictly matches case while "reqirep" ignores case. <string> is the complete line to be added. Any space or known delimiter must be escaped using a backslash ('\'). References to matched pattern groups are possible using the common \N form, with N being a single digit between 0 and 9. Please refer to section 6 about HTTP header manipulation for more information. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. Any line matching extended regular expression <search> in the request (both the request line and header lines) will be completely replaced with <string>. Most common use of this is to rewrite URLs or domain names in "Host" headers. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Note that for increased readability, it is suggested to add enough spaces between the request and the response. Keep in mind that URLs in request line are case-sensitive while header names are not. Example : # replace "/static/" with "/" at the beginning of any request path. reqrep ^([^\ :]*)\ /static/(.*) \1\ /\2 # replace "www.mydomain.com" with "www" in the host name. reqirep ^Host:\ www.mydomain.com Host:\ www See also: "reqadd", "reqdel", "rsprep", "tune.bufsize", section 6 about HTTP header manipulation, and section 7 about ACLs. reqtarpit <search> [{if | unless} <cond>] reqitarpit <search> [{if | unless} <cond>] (ignore case) Tarpit an HTTP request containing a line matching a regular expression May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the request line. This is an extended regular expression. Parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "reqtarpit" keyword strictly matches case while "reqitarpit" ignores case. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. A request containing any line which matches extended regular expression <search> will be tarpitted, which means that it will connect to nowhere, will be kept open for a pre-defined time, then will return an HTTP error 500 so that the attacker does not suspect it has been tarpitted. The status 500 will be reported in the logs, but the completion flags will indicate "PT". The delay is defined by "timeout tarpit", or "timeout connect" if the former is not set. The goal of the tarpit is to slow down robots attacking servers with identifiable requests. Many robots limit their outgoing number of connections and stay connected waiting for a reply which can take several minutes to come. Depending on the environment and attack, it may be particularly efficient at reducing the load on the network and firewalls. Examples : # ignore user-agents reporting any flavour of "Mozilla" or "MSIE", but # block all others. reqipass ^User-Agent:\.*(Mozilla|MSIE) reqitarpit ^User-Agent: # block bad guys acl badguys src 10.1.0.3 172.16.13.20/28 reqitarpit . if badguys See also: "reqallow", "reqdeny", "reqpass", section 6 about HTTP header manipulation, and section 7 about ACLs. retries <value> Set the number of retries to perform on a server after a connection failure May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes Arguments : <value> is the number of times a connection attempt should be retried on a server when a connection either is refused or times out. The default value is 3. It is important to understand that this value applies to the number of connection attempts, not full requests. When a connection has effectively been established to a server, there will be no more retry. In order to avoid immediate reconnections to a server which is restarting, a turn-around timer of 1 second is applied before a retry occurs. When "option redispatch" is set, the last retry may be performed on another server even if a cookie references a different server. See also : "option redispatch" rspadd <string> [{if | unless} <cond>] Add a header at the end of the HTTP response May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <string> is the complete line to be added. Any space or known delimiter must be escaped using a backslash ('\'). Please refer to section 6 about HTTP header manipulation for more information. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. A new line consisting in <string> followed by a line feed will be added after the last header of an HTTP response. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. See also: "reqadd", section 6 about HTTP header manipulation, and section 7 about ACLs. rspdel <search> [{if | unless} <cond>] rspidel <search> [{if | unless} <cond>] (ignore case) Delete all headers matching a regular expression in an HTTP response May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the response line. This is an extended regular expression, so parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "rspdel" keyword strictly matches case while "rspidel" ignores case. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. Any header line matching extended regular expression <search> in the response will be completely deleted. Most common use of this is to remove unwanted and/or sensitive headers or cookies from a response before passing it to the client. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Keep in mind that header names are not case-sensitive. Example : # remove the Server header from responses rspidel ^Server:.* See also: "rspadd", "rsprep", "reqdel", section 6 about HTTP header manipulation, and section 7 about ACLs. rspdeny <search> [{if | unless} <cond>] rspideny <search> [{if | unless} <cond>] (ignore case) Block an HTTP response if a line matches a regular expression May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the response line. This is an extended regular expression, so parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "rspdeny" keyword strictly matches case while "rspideny" ignores case. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. A response containing any line which matches extended regular expression <search> will mark the request as denied. The test applies both to the response line and to response headers. Keep in mind that header names are not case-sensitive. Main use of this keyword is to prevent sensitive information leak and to block the response before it reaches the client. If a response is denied, it will be replaced with an HTTP 502 error so that the client never retrieves any sensitive data. It is easier, faster and more powerful to use ACLs to write access policies. Rspdeny should be avoided in new designs. Example : # Ensure that no content type matching ms-word will leak rspideny ^Content-type:\.*/ms-word See also: "reqdeny", "acl", "block", section 6 about HTTP header manipulation and section 7 about ACLs. rsprep <search> <string> [{if | unless} <cond>] rspirep <search> <string> [{if | unless} <cond>] (ignore case) Replace a regular expression with a string in an HTTP response line May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <search> is the regular expression applied to HTTP headers and to the response line. This is an extended regular expression, so parenthesis grouping is supported and no preliminary backslash is required. Any space or known delimiter must be escaped using a backslash ('\'). The pattern applies to a full line at a time. The "rsprep" keyword strictly matches case while "rspirep" ignores case. <string> is the complete line to be added. Any space or known delimiter must be escaped using a backslash ('\'). References to matched pattern groups are possible using the common \N form, with N being a single digit between 0 and 9. Please refer to section 6 about HTTP header manipulation for more information. <cond> is an optional matching condition built from ACLs. It makes it possible to ignore this rule when other conditions are not met. Any line matching extended regular expression <search> in the response (both the response line and header lines) will be completely replaced with <string>. Most common use of this is to rewrite Location headers. Header transformations only apply to traffic which passes through HAProxy, and not to traffic generated by HAProxy, such as health-checks or error responses. Note that for increased readability, it is suggested to add enough spaces between the request and the response. Keep in mind that header names are not case-sensitive. Example : # replace "Location: 127.0.0.1:8080" with "Location: www.mydomain.com" rspirep ^Location:\ 127.0.0.1:8080 Location:\ www.mydomain.com See also: "rspadd", "rspdel", "reqrep", section 6 about HTTP header manipulation, and section 7 about ACLs. server <name> <address>[:[port]] [param*] Declare a server in a backend May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <name> is the internal name assigned to this server. This name will appear in logs and alerts. If "http-send-name-header" is set, it will be added to the request header sent to the server. <address> is the IPv4 or IPv6 address of the server. Alternatively, a resolvable hostname is supported, but this name will be resolved during start-up. Address "0.0.0.0" or "*" has a special meaning. It indicates that the connection will be forwarded to the same IP address as the one from the client connection. This is useful in transparent proxy architectures where the client's connection is intercepted and haproxy must forward to the original destination address. This is more or less what the "transparent" keyword does except that with a server it's possible to limit concurrency and to report statistics. Optionally, an address family prefix may be used before the address to force the family regardless of the address format, which can be useful to specify a path to a unix socket with no slash ('/'). Currently supported prefixes are : - 'ipv4@' -> address is always IPv4 - 'ipv6@' -> address is always IPv6 - 'unix@' -> address is a path to a local unix socket - 'abns@' -> address is in abstract namespace (Linux only) Any part of the address string may reference any number of environment variables by preceding their name with a dollar sign ('$') and optionally enclosing them with braces ('{}'), similarly to what is done in Bourne shell. <port> is an optional port specification. If set, all connections will be sent to this port. If unset, the same port the client connected to will be used. The port may also be prefixed by a "+" or a "-". In this case, the server's port will be determined by adding this value to the client's port. <param*> is a list of parameters for this server. The "server" keywords accepts an important number of options and has a complete section dedicated to it. Please refer to section 5 for more details. Examples : server first 10.1.1.1:1080 cookie first check inter 1000 server second 10.1.1.2:1080 cookie second check inter 1000 server transp ipv4@ server backup ${SRV_BACKUP}:1080 backup server www1_dc1 ${LAN_DC1}.101:80 server www1_dc2 ${LAN_DC2}.101:80 See also: "default-server", "http-send-name-header" and section 5 about server options source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | client | clientip } ] source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | hdr_ip(<hdr>[,<occ>]) } ] source <addr>[:<port>] [interface <name>] Set the source address for outgoing connections May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <addr> is the IPv4 address HAProxy will bind to before connecting to a server. This address is also used as a source for health checks. The default value of 0.0.0.0 means that the system will select the most appropriate address to reach its destination. Optionally an address family prefix may be used before the address to force the family regardless of the address format, which can be useful to specify a path to a unix socket with no slash ('/'). Currently supported prefixes are : - 'ipv4@' -> address is always IPv4 - 'ipv6@' -> address is always IPv6 - 'unix@' -> address is a path to a local unix socket - 'abns@' -> address is in abstract namespace (Linux only) Any part of the address string may reference any number of environment variables by preceding their name with a dollar sign ('$') and optionally enclosing them with braces ('{}'), similarly to what is done in Bourne shell. <port> is an optional port. It is normally not needed but may be useful in some very specific contexts. The default value of zero means the system will select a free port. Note that port ranges are not supported in the backend. If you want to force port ranges, you have to specify them on each "server" line. <addr2> is the IP address to present to the server when connections are forwarded in full transparent proxy mode. This is currently only supported on some patched Linux kernels. When this address is specified, clients connecting to the server will be presented with this address, while health checks will still use the address <addr>. <port2> is the optional port to present to the server when connections are forwarded in full transparent proxy mode (see <addr2> above). The default value of zero means the system will select a free port. <hdr> is the name of a HTTP header in which to fetch the IP to bind to. This is the name of a comma-separated header list which can contain multiple IP addresses. By default, the last occurrence is used. This is designed to work with the X-Forwarded-For header and to automatically bind to the client's IP address as seen by previous proxy, typically Stunnel. In order to use another occurrence from the last one, please see the <occ> parameter below. When the header (or occurrence) is not found, no binding is performed so that the proxy's default IP address is used. Also keep in mind that the header name is case insensitive, as for any HTTP header. <occ> is the occurrence number of a value to be used in a multi-value header. This is to be used in conjunction with "hdr_ip(<hdr>)", in order to specify which occurrence to use for the source IP address. Positive values indicate a position from the first occurrence, 1 being the first one. Negative values indicate positions relative to the last one, -1 being the last one. This is helpful for situations where an X-Forwarded-For header is set at the entry point of an infrastructure and must be used several proxy layers away. When this value is not specified, -1 is assumed. Passing a zero here disables the feature. <name> is an optional interface name to which to bind to for outgoing traffic. On systems supporting this features (currently, only Linux), this allows one to bind all traffic to the server to this interface even if it is not the one the system would select based on routing tables. This should be used with extreme care. Note that using this option requires root privileges. The "source" keyword is useful in complex environments where a specific address only is allowed to connect to the servers. It may be needed when a private address must be used through a public gateway for instance, and it is known that the system cannot determine the adequate source address by itself. An extension which is available on certain patched Linux kernels may be used through the "usesrc" optional keyword. It makes it possible to connect to the servers with an IP address which does not belong to the system itself. This is called "full transparent proxy mode". For this to work, the destination servers have to route their traffic back to this address through the machine running HAProxy, and IP forwarding must generally be enabled on this machine. In this "full transparent proxy" mode, it is possible to force a specific IP address to be presented to the servers. This is not much used in fact. A more common use is to tell HAProxy to present the client's IP address. For this, there are two methods : - present the client's IP and port addresses. This is the most transparent mode, but it can cause problems when IP connection tracking is enabled on the machine, because a same connection may be seen twice with different states. However, this solution presents the huge advantage of not limiting the system to the 64k outgoing address+port couples, because all of the client ranges may be used. - present only the client's IP address and select a spare port. This solution is still quite elegant but slightly less transparent (downstream firewalls logs will not match upstream's). It also presents the downside of limiting the number of concurrent connections to the usual 64k ports. However, since the upstream and downstream ports are different, local IP connection tracking on the machine will not be upset by the reuse of the same session. Note that depending on the transparent proxy technology used, it may be required to force the source address. In fact, cttproxy version 2 requires an IP address in <addr> above, and does not support setting of "0.0.0.0" as the IP address because it creates NAT entries which much match the exact outgoing address. Tproxy version 4 and some other kernel patches which work in pure forwarding mode generally will not have this limitation. This option sets the default source for all servers in the backend. It may also be specified in a "defaults" section. Finer source address specification is possible at the server level using the "source" server option. Refer to section 5 for more information. Examples : backend private # Connect to the servers using our 192.168.1.200 source address source 192.168.1.200 backend transparent_ssl1 # Connect to the SSL farm from the client's source address source 192.168.1.200 usesrc clientip backend transparent_ssl2 # Connect to the SSL farm from the client's source address and port # not recommended if IP conntrack is present on the local machine. source 192.168.1.200 usesrc client backend transparent_ssl3 # Connect to the SSL farm from the client's source address. It # is more conntrack-friendly. source 192.168.1.200 usesrc clientip backend transparent_smtp # Connect to the SMTP farm from the client's source address/port # with Tproxy version 4. source 0.0.0.0 usesrc clientip backend transparent_http # Connect to the servers using the client's IP as seen by previous # proxy. source 0.0.0.0 usesrc hdr_ip(x-forwarded-for,-1) See also : the "source" server option in section 5, the Tproxy patches for the Linux kernel on www.balabit.com, the "bind" keyword. srvtimeout <timeout> (deprecated) Set the maximum inactivity time on the server side. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. The inactivity timeout applies when the server is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase of the server's response, when it has to send the headers, as it directly represents the server's processing time for the request. To find out what value to put there, it's often good to start with what would be considered as unacceptable response times, then check the logs to observe the response time distribution, and adjust the value accordingly. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. Whatever the expected server response times, it is a good practice to cover at least one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds minimum). This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter is provided for compatibility but is currently deprecated. Please use "timeout server" instead. See also : "timeout server", "timeout tunnel", "timeout client" and "clitimeout". stats admin { if | unless } <cond> Enable statistics admin level if/unless a condition is matched May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes This statement enables the statistics admin level if/unless a condition is matched. The admin level allows to enable/disable servers from the web interface. By default, statistics page is read-only for security reasons. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours. Currently, the POST request is limited to the buffer size minus the reserved buffer space, which means that if the list of servers is too long, the request won't be processed. It is recommended to alter few servers at a time. Example : # statistics admin level only for localhost backend stats_localhost stats enable stats admin if LOCALHOST Example : # statistics admin level always enabled because of the authentication backend stats_auth stats enable stats auth admin:AdMiN123 stats admin if TRUE Example : # statistics admin level depends on the authenticated user userlist stats-auth group admin users admin user admin insecure-password AdMiN123 group readonly users haproxy user haproxy insecure-password haproxy backend stats_auth stats enable acl AUTH http_auth(stats-auth) acl AUTH_ADMIN http_auth_group(stats-auth) admin stats http-request auth unless AUTH stats admin if AUTH_ADMIN See also : "stats enable", "stats auth", "stats http-request", "nbproc", "bind-process", section 3.4 about userlists and section 7 about ACL usage. stats auth <user>:<passwd> Enable statistics with authentication and grant access to an account May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <user> is a user name to grant access to <passwd> is the cleartext password associated to this user This statement enables statistics with default settings, and restricts access to declared users only. It may be repeated as many times as necessary to allow as many users as desired. When a user tries to access the statistics without a valid account, a "401 Forbidden" response will be returned so that the browser asks the user to provide a valid user and password. The real which will be returned to the browser is configurable using "stats realm". Since the authentication method is HTTP Basic Authentication, the passwords circulate in cleartext on the network. Thus, it was decided that the configuration file would also use cleartext passwords to remind the users that those ones should not be sensitive and not shared with any other account. It is also possible to reduce the scope of the proxies which appear in the report using "stats scope". Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example : # public access (limited to this backend only) backend public_www server srv1 192.168.0.1:80 stats enable stats hide-version stats scope . stats uri /admin?stats stats realm Haproxy\ Statistics stats auth admin1:AdMiN123 stats auth admin2:AdMiN321 # internal monitoring access (unlimited) backend private_monitoring stats enable stats uri /admin?stats stats refresh 5s See also : "stats enable", "stats realm", "stats scope", "stats uri" stats enable Enable statistics reporting with default settings May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none This statement enables statistics reporting with default settings defined at build time. Unless stated otherwise, these settings are used : - stats uri : /haproxy?stats - stats realm : "HAProxy Statistics" - stats auth : no authentication - stats scope : no restriction Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example : # public access (limited to this backend only) backend public_www server srv1 192.168.0.1:80 stats enable stats hide-version stats scope . stats uri /admin?stats stats realm Haproxy\ Statistics stats auth admin1:AdMiN123 stats auth admin2:AdMiN321 # internal monitoring access (unlimited) backend private_monitoring stats enable stats uri /admin?stats stats refresh 5s See also : "stats auth", "stats realm", "stats uri" stats hide-version Enable statistics and hide HAProxy version reporting May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none By default, the stats page reports some useful status information along with the statistics. Among them is HAProxy's version. However, it is generally considered dangerous to report precise version to anyone, as it can help them target known weaknesses with specific attacks. The "stats hide-version" statement removes the version from the statistics report. This is recommended for public sites or any site with a weak login/password. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example : # public access (limited to this backend only) backend public_www server srv1 192.168.0.1:80 stats enable stats hide-version stats scope . stats uri /admin?stats stats realm Haproxy\ Statistics stats auth admin1:AdMiN123 stats auth admin2:AdMiN321 # internal monitoring access (unlimited) backend private_monitoring stats enable stats uri /admin?stats stats refresh 5s See also : "stats auth", "stats enable", "stats realm", "stats uri" stats http-request { allow | deny | auth [realm <realm>] } [ { if | unless } <condition> ] Access control for statistics May be used in sections: defaults | frontend | listen | backend no | no | yes | yes As "http-request", these set of options allow to fine control access to statistics. Each option may be followed by if/unless and acl. First option with matched condition (or option without condition) is final. For "deny" a 403 error will be returned, for "allow" normal processing is performed, for "auth" a 401/407 error code is returned so the client should be asked to enter a username and password. There is no fixed limit to the number of http-request statements per instance. See also : "http-request", section 3.4 about userlists and section 7 about ACL usage. stats realm <realm> Enable statistics and set authentication realm May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <realm> is the name of the HTTP Basic Authentication realm reported to the browser. The browser uses it to display it in the pop-up inviting the user to enter a valid username and password. The realm is read as a single word, so any spaces in it should be escaped using a backslash ('\'). This statement is useful only in conjunction with "stats auth" since it is only related to authentication. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example : # public access (limited to this backend only) backend public_www server srv1 192.168.0.1:80 stats enable stats hide-version stats scope . stats uri /admin?stats stats realm Haproxy\ Statistics stats auth admin1:AdMiN123 stats auth admin2:AdMiN321 # internal monitoring access (unlimited) backend private_monitoring stats enable stats uri /admin?stats stats refresh 5s See also : "stats auth", "stats enable", "stats uri" stats refresh <delay> Enable statistics with automatic refresh May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <delay> is the suggested refresh delay, specified in seconds, which will be returned to the browser consulting the report page. While the browser is free to apply any delay, it will generally respect it and refresh the page this every seconds. The refresh interval may be specified in any other non-default time unit, by suffixing the unit after the value, as explained at the top of this document. This statement is useful on monitoring displays with a permanent page reporting the load balancer's activity. When set, the HTML report page will include a link "refresh"/"stop refresh" so that the user can select whether he wants automatic refresh of the page or not. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example : # public access (limited to this backend only) backend public_www server srv1 192.168.0.1:80 stats enable stats hide-version stats scope . stats uri /admin?stats stats realm Haproxy\ Statistics stats auth admin1:AdMiN123 stats auth admin2:AdMiN321 # internal monitoring access (unlimited) backend private_monitoring stats enable stats uri /admin?stats stats refresh 5s See also : "stats auth", "stats enable", "stats realm", "stats uri" stats scope { <name> | "." } Enable statistics and limit access scope May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <name> is the name of a listen, frontend or backend section to be reported. The special name "." (a single dot) designates the section in which the statement appears. When this statement is specified, only the sections enumerated with this statement will appear in the report. All other ones will be hidden. This statement may appear as many times as needed if multiple sections need to be reported. Please note that the name checking is performed as simple string comparisons, and that it is never checked that a give section name really exists. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example : # public access (limited to this backend only) backend public_www server srv1 192.168.0.1:80 stats enable stats hide-version stats scope . stats uri /admin?stats stats realm Haproxy\ Statistics stats auth admin1:AdMiN123 stats auth admin2:AdMiN321 # internal monitoring access (unlimited) backend private_monitoring stats enable stats uri /admin?stats stats refresh 5s See also : "stats auth", "stats enable", "stats realm", "stats uri" stats show-desc [ <desc> ] Enable reporting of a description on the statistics page. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes <desc> is an optional description to be reported. If unspecified, the description from global section is automatically used instead. This statement is useful for users that offer shared services to their customers, where node or description should be different for each customer. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. By default description is not shown. Example : # internal monitoring access (unlimited) backend private_monitoring stats enable stats show-desc Master node for Europe, Asia, Africa stats uri /admin?stats stats refresh 5s See also: "show-node", "stats enable", "stats uri" and "description" in global section. stats show-legends Enable reporting additional information on the statistics page May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : none Enable reporting additional information on the statistics page : - cap: capabilities (proxy) - mode: one of tcp, http or health (proxy) - id: SNMP ID (proxy, socket, server) - IP (socket, server) - cookie (backend, server) Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Default behaviour is not to show this information. See also: "stats enable", "stats uri". stats show-node [ <name> ] Enable reporting of a host name on the statistics page. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments: <name> is an optional name to be reported. If unspecified, the node name from global section is automatically used instead. This statement is useful for users that offer shared services to their customers, where node or description might be different on a stats page provided for each customer. Default behaviour is not to show host name. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example: # internal monitoring access (unlimited) backend private_monitoring stats enable stats show-node Europe-1 stats uri /admin?stats stats refresh 5s See also: "show-desc", "stats enable", "stats uri", and "node" in global section. stats uri <prefix> Enable statistics and define the URI prefix to access them May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <prefix> is the prefix of any URI which will be redirected to stats. This prefix may contain a question mark ('?') to indicate part of a query string. The statistics URI is intercepted on the relayed traffic, so it appears as a page within the normal application. It is strongly advised to ensure that the selected URI will never appear in the application, otherwise it will never be possible to reach it in the application. The default URI compiled in haproxy is "/haproxy?stats", but this may be changed at build time, so it's better to always explicitly specify it here. It is generally a good idea to include a question mark in the URI so that intermediate proxies refrain from caching the results. Also, since any string beginning with the prefix will be accepted as a stats request, the question mark helps ensuring that no valid URI will begin with the same words. It is sometimes very convenient to use "/" as the URI prefix, and put that statement in a "listen" instance of its own. That makes it easy to dedicate an address or a port to statistics only. Though this statement alone is enough to enable statistics reporting, it is recommended to set all other settings in order to avoid relying on default unobvious parameters. Example : # public access (limited to this backend only) backend public_www server srv1 192.168.0.1:80 stats enable stats hide-version stats scope . stats uri /admin?stats stats realm Haproxy\ Statistics stats auth admin1:AdMiN123 stats auth admin2:AdMiN321 # internal monitoring access (unlimited) backend private_monitoring stats enable stats uri /admin?stats stats refresh 5s See also : "stats auth", "stats enable", "stats realm" stick match <pattern> [table <table>] [{if | unless} <cond>] Define a request pattern matching condition to stick a user to a server May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <pattern> is a sample expression rule as described in section 7.3. It describes what elements of the incoming request or connection will be analysed in the hope to find a matching entry in a stickiness table. This rule is mandatory. <table> is an optional stickiness table name. If unspecified, the same backend's table is used. A stickiness table is declared using the "stick-table" statement. <cond> is an optional matching condition. It makes it possible to match on a certain criterion only when other conditions are met (or not met). For instance, it could be used to match on a source IP address except when a request passes through a known proxy, in which case we'd match on a header containing that IP address. Some protocols or applications require complex stickiness rules and cannot always simply rely on cookies nor hashing. The "stick match" statement describes a rule to extract the stickiness criterion from an incoming request or connection. See section 7 for a complete list of possible patterns and transformation rules. The table has to be declared using the "stick-table" statement. It must be of a type compatible with the pattern. By default it is the one which is present in the same backend. It is possible to share a table with other backends by referencing it using the "table" keyword. If another table is referenced, the server's ID inside the backends are used. By default, all server IDs start at 1 in each backend, so the server ordering is enough. But in case of doubt, it is highly recommended to force server IDs using their "id" setting. It is possible to restrict the conditions where a "stick match" statement will apply, using "if" or "unless" followed by a condition. See section 7 for ACL based conditions. There is no limit on the number of "stick match" statements. The first that applies and matches will cause the request to be directed to the same server as was used for the request which created the entry. That way, multiple matches can be used as fallbacks. The stick rules are checked after the persistence cookies, so they will not affect stickiness if a cookie has already been used to select a server. That way, it becomes very easy to insert cookies and match on IP addresses in order to maintain stickiness between HTTP and HTTPS. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours. Example : # forward SMTP users to the same server they just used for POP in the # last 30 minutes backend pop mode tcp balance roundrobin stick store-request src stick-table type ip size 200k expire 30m server s1 192.168.1.1:110 server s2 192.168.1.1:110 backend smtp mode tcp balance roundrobin stick match src table pop server s1 192.168.1.1:25 server s2 192.168.1.1:25 See also : "stick-table", "stick on", "nbproc", "bind-process" and section 7 about ACLs and samples fetching. stick on <pattern> [table <table>] [{if | unless} <condition>] Define a request pattern to associate a user to a server May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Note : This form is exactly equivalent to "stick match" followed by "stick store-request", all with the same arguments. Please refer to both keywords for details. It is only provided as a convenience for writing more maintainable configurations. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours. Examples : # The following form ... stick on src table pop if !localhost # ...is strictly equivalent to this one : stick match src table pop if !localhost stick store-request src table pop if !localhost # Use cookie persistence for HTTP, and stick on source address for HTTPS as # well as HTTP without cookie. Share the same table between both accesses. backend http mode http balance roundrobin stick on src table https cookie SRV insert indirect nocache server s1 192.168.1.1:80 cookie s1 server s2 192.168.1.1:80 cookie s2 backend https mode tcp balance roundrobin stick-table type ip size 200k expire 30m stick on src server s1 192.168.1.1:443 server s2 192.168.1.1:443 See also : "stick match", "stick store-request", "nbproc" and "bind-process". stick store-request <pattern> [table <table>] [{if | unless} <condition>] Define a request pattern used to create an entry in a stickiness table May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <pattern> is a sample expression rule as described in section 7.3. It describes what elements of the incoming request or connection will be analysed, extracted and stored in the table once a server is selected. <table> is an optional stickiness table name. If unspecified, the same backend's table is used. A stickiness table is declared using the "stick-table" statement. <cond> is an optional storage condition. It makes it possible to store certain criteria only when some conditions are met (or not met). For instance, it could be used to store the source IP address except when the request passes through a known proxy, in which case we'd store a converted form of a header containing that IP address. Some protocols or applications require complex stickiness rules and cannot always simply rely on cookies nor hashing. The "stick store-request" statement describes a rule to decide what to extract from the request and when to do it, in order to store it into a stickiness table for further requests to match it using the "stick match" statement. Obviously the extracted part must make sense and have a chance to be matched in a further request. Storing a client's IP address for instance often makes sense. Storing an ID found in a URL parameter also makes sense. Storing a source port will almost never make any sense because it will be randomly matched. See section 7 for a complete list of possible patterns and transformation rules. The table has to be declared using the "stick-table" statement. It must be of a type compatible with the pattern. By default it is the one which is present in the same backend. It is possible to share a table with other backends by referencing it using the "table" keyword. If another table is referenced, the server's ID inside the backends are used. By default, all server IDs start at 1 in each backend, so the server ordering is enough. But in case of doubt, it is highly recommended to force server IDs using their "id" setting. It is possible to restrict the conditions where a "stick store-request" statement will apply, using "if" or "unless" followed by a condition. This condition will be evaluated while parsing the request, so any criteria can be used. See section 7 for ACL based conditions. There is no limit on the number of "stick store-request" statements, but there is a limit of 8 simultaneous stores per request or response. This makes it possible to store up to 8 criteria, all extracted from either the request or the response, regardless of the number of rules. Only the 8 first ones which match will be kept. Using this, it is possible to feed multiple tables at once in the hope to increase the chance to recognize a user on another protocol or access method. Using multiple store-request rules with the same table is possible and may be used to find the best criterion to rely on, by arranging the rules by decreasing preference order. Only the first extracted criterion for a given table will be stored. All subsequent store- request rules referencing the same table will be skipped and their ACLs will not be evaluated. The "store-request" rules are evaluated once the server connection has been established, so that the table will contain the real server that processed the request. Note : Consider not using this feature in multi-process mode (nbproc > 1) unless you know what you do : memory is not shared between the processes, which can result in random behaviours. Example : # forward SMTP users to the same server they just used for POP in the # last 30 minutes backend pop mode tcp balance roundrobin stick store-request src stick-table type ip size 200k expire 30m server s1 192.168.1.1:110 server s2 192.168.1.1:110 backend smtp mode tcp balance roundrobin stick match src table pop server s1 192.168.1.1:25 server s2 192.168.1.1:25 See also : "stick-table", "stick on", "nbproc", "bind-process" and section 7 about ACLs and sample fetching. stick-table type {ip | integer | string [len <length>] | binary [len <length>]} size <size> [expire <expire>] [nopurge] [peers <peersect>] [store <data_type>]* Configure the stickiness table for the current section May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : ip a table declared with "type ip" will only store IPv4 addresses. This form is very compact (about 50 bytes per entry) and allows very fast entry lookup and stores with almost no overhead. This is mainly used to store client source IP addresses. ipv6 a table declared with "type ipv6" will only store IPv6 addresses. This form is very compact (about 60 bytes per entry) and allows very fast entry lookup and stores with almost no overhead. This is mainly used to store client source IP addresses. integer a table declared with "type integer" will store 32bit integers which can represent a client identifier found in a request for instance. string a table declared with "type string" will store substrings of up to <len> characters. If the string provided by the pattern extractor is larger than <len>, it will be truncated before being stored. During matching, at most <len> characters will be compared between the string in the table and the extracted pattern. When not specified, the string is automatically limited to 32 characters. binary a table declared with "type binary" will store binary blocks of <len> bytes. If the block provided by the pattern extractor is larger than <len>, it will be truncated before being stored. If the block provided by the sample expression is shorter than <len>, it will be padded by 0. When not specified, the block is automatically limited to 32 bytes. <length> is the maximum number of characters that will be stored in a "string" type table (See type "string" above). Or the number of bytes of the block in "binary" type table. Be careful when changing this parameter as memory usage will proportionally increase. <size> is the maximum number of entries that can fit in the table. This value directly impacts memory usage. Count approximately 50 bytes per entry, plus the size of a string if any. The size supports suffixes "k", "m", "g" for 2^10, 2^20 and 2^30 factors. [nopurge] indicates that we refuse to purge older entries when the table is full. When not specified and the table is full when haproxy wants to store an entry in it, it will flush a few of the oldest entries in order to release some space for the new ones. This is most often the desired behaviour. In some specific cases, it be desirable to refuse new entries instead of purging the older ones. That may be the case when the amount of data to store is far above the hardware limits and we prefer not to offer access to new clients than to reject the ones already connected. When using this parameter, be sure to properly set the "expire" parameter (see below). <peersect> is the name of the peers section to use for replication. Entries which associate keys to server IDs are kept synchronized with the remote peers declared in this section. All entries are also automatically learned from the local peer (old process) during a soft restart. NOTE : each peers section may be referenced only by tables belonging to the same unique process. <expire> defines the maximum duration of an entry in the table since it was last created, refreshed or matched. The expiration delay is defined using the standard time format, similarly as the various timeouts. The maximum duration is slightly above 24 days. See section 2.2 for more information. If this delay is not specified, the session won't automatically expire, but older entries will be removed once full. Be sure not to use the "nopurge" parameter if not expiration delay is specified. <data_type> is used to store additional information in the stick-table. This may be used by ACLs in order to control various criteria related to the activity of the client matching the stick-table. For each item specified here, the size of each entry will be inflated so that the additional data can fit. Several data types may be stored with an entry. Multiple data types may be specified after the "store" keyword, as a comma-separated list. Alternatively, it is possible to repeat the "store" keyword followed by one or several data types. Except for the "server_id" type which is automatically detected and enabled, all data types must be explicitly declared to be stored. If an ACL references a data type which is not stored, the ACL will simply not match. Some data types require an argument which must be passed just after the type between parenthesis. See below for the supported data types and their arguments. The data types that can be stored with an entry are the following : - server_id : this is an integer which holds the numeric ID of the server a request was assigned to. It is used by the "stick match", "stick store", and "stick on" rules. It is automatically enabled when referenced. - gpc0 : first General Purpose Counter. It is a positive 32-bit integer integer which may be used for anything. Most of the time it will be used to put a special tag on some entries, for instance to note that a specific behaviour was detected and must be known for future matches. - gpc0_rate(<period>) : increment rate of the first General Purpose Counter over a period. It is a positive 32-bit integer integer which may be used for anything. Just like <gpc0>, it counts events, but instead of keeping a cumulative count, it maintains the rate at which the counter is incremented. Most of the time it will be used to measure the frequency of occurrence of certain events (eg: requests to a specific URL). - conn_cnt : Connection Count. It is a positive 32-bit integer which counts the absolute number of connections received from clients which matched this entry. It does not mean the connections were accepted, just that they were received. - conn_cur : Current Connections. It is a positive 32-bit integer which stores the concurrent connection counts for the entry. It is incremented once an incoming connection matches the entry, and decremented once the connection leaves. That way it is possible to know at any time the exact number of concurrent connections for an entry. - conn_rate(<period>) : frequency counter (takes 12 bytes). It takes an integer parameter <period> which indicates in milliseconds the length of the period over which the average is measured. It reports the average incoming connection rate over that period, in connections per period. The result is an integer which can be matched using ACLs. - sess_cnt : Session Count. It is a positive 32-bit integer which counts the absolute number of sessions received from clients which matched this entry. A session is a connection that was accepted by the layer 4 rules. - sess_rate(<period>) : frequency counter (takes 12 bytes). It takes an integer parameter <period> which indicates in milliseconds the length of the period over which the average is measured. It reports the average incoming session rate over that period, in sessions per period. The result is an integer which can be matched using ACLs. - http_req_cnt : HTTP request Count. It is a positive 32-bit integer which counts the absolute number of HTTP requests received from clients which matched this entry. It does not matter whether they are valid requests or not. Note that this is different from sessions when keep-alive is used on the client side. - http_req_rate(<period>) : frequency counter (takes 12 bytes). It takes an integer parameter <period> which indicates in milliseconds the length of the period over which the average is measured. It reports the average HTTP request rate over that period, in requests per period. The result is an integer which can be matched using ACLs. It does not matter whether they are valid requests or not. Note that this is different from sessions when keep-alive is used on the client side. - http_err_cnt : HTTP Error Count. It is a positive 32-bit integer which counts the absolute number of HTTP requests errors induced by clients which matched this entry. Errors are counted on invalid and truncated requests, as well as on denied or tarpitted requests, and on failed authentications. If the server responds with 4xx, then the request is also counted as an error since it's an error triggered by the client (eg: vulnerability scan). - http_err_rate(<period>) : frequency counter (takes 12 bytes). It takes an integer parameter <period> which indicates in milliseconds the length of the period over which the average is measured. It reports the average HTTP request error rate over that period, in requests per period (see http_err_cnt above for what is accounted as an error). The result is an integer which can be matched using ACLs. - bytes_in_cnt : client to server byte count. It is a positive 64-bit integer which counts the cumulated amount of bytes received from clients which matched this entry. Headers are included in the count. This may be used to limit abuse of upload features on photo or video servers. - bytes_in_rate(<period>) : frequency counter (takes 12 bytes). It takes an integer parameter <period> which indicates in milliseconds the length of the period over which the average is measured. It reports the average incoming bytes rate over that period, in bytes per period. It may be used to detect users which upload too much and too fast. Warning: with large uploads, it is possible that the amount of uploaded data will be counted once upon termination, thus causing spikes in the average transfer speed instead of having a smooth one. This may partially be smoothed with "option contstats" though this is not perfect yet. Use of byte_in_cnt is recommended for better fairness. - bytes_out_cnt : server to client byte count. It is a positive 64-bit integer which counts the cumulated amount of bytes sent to clients which matched this entry. Headers are included in the count. This may be used to limit abuse of bots sucking the whole site. - bytes_out_rate(<period>) : frequency counter (takes 12 bytes). It takes an integer parameter <period> which indicates in milliseconds the length of the period over which the average is measured. It reports the average outgoing bytes rate over that period, in bytes per period. It may be used to detect users which download too much and too fast. Warning: with large transfers, it is possible that the amount of transferred data will be counted once upon termination, thus causing spikes in the average transfer speed instead of having a smooth one. This may partially be smoothed with "option contstats" though this is not perfect yet. Use of byte_out_cnt is recommended for better fairness. There is only one stick-table per proxy. At the moment of writing this doc, it does not seem useful to have multiple tables per proxy. If this happens to be required, simply create a dummy backend with a stick-table in it and reference it. It is important to understand that stickiness based on learning information has some limitations, including the fact that all learned associations are lost upon restart. In general it can be good as a complement but not always as an exclusive stickiness. Last, memory requirements may be important when storing many data types. Indeed, storing all indicators above at once in each entry requires 116 bytes per entry, or 116 MB for a 1-million entries table. This is definitely not something that can be ignored. Example: # Keep track of counters of up to 1 million IP addresses over 5 minutes # and store a general purpose counter and the average connection rate # computed over a sliding window of 30 seconds. stick-table type ip size 1m expire 5m store gpc0,conn_rate(30s) See also : "stick match", "stick on", "stick store-request", section 2.2 about time format and section 7 about ACLs. stick store-response <pattern> [table <table>] [{if | unless} <condition>] Define a request pattern used to create an entry in a stickiness table May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <pattern> is a sample expression rule as described in section 7.3. It describes what elements of the response or connection will be analysed, extracted and stored in the table once a server is selected. <table> is an optional stickiness table name. If unspecified, the same backend's table is used. A stickiness table is declared using the "stick-table" statement. <cond> is an optional storage condition. It makes it possible to store certain criteria only when some conditions are met (or not met). For instance, it could be used to store the SSL session ID only when the response is a SSL server hello. Some protocols or applications require complex stickiness rules and cannot always simply rely on cookies nor hashing. The "stick store-response" statement describes a rule to decide what to extract from the response and when to do it, in order to store it into a stickiness table for further requests to match it using the "stick match" statement. Obviously the extracted part must make sense and have a chance to be matched in a further request. Storing an ID found in a header of a response makes sense. See section 7 for a complete list of possible patterns and transformation rules. The table has to be declared using the "stick-table" statement. It must be of a type compatible with the pattern. By default it is the one which is present in the same backend. It is possible to share a table with other backends by referencing it using the "table" keyword. If another table is referenced, the server's ID inside the backends are used. By default, all server IDs start at 1 in each backend, so the server ordering is enough. But in case of doubt, it is highly recommended to force server IDs using their "id" setting. It is possible to restrict the conditions where a "stick store-response" statement will apply, using "if" or "unless" followed by a condition. This condition will be evaluated while parsing the response, so any criteria can be used. See section 7 for ACL based conditions. There is no limit on the number of "stick store-response" statements, but there is a limit of 8 simultaneous stores per request or response. This makes it possible to store up to 8 criteria, all extracted from either the request or the response, regardless of the number of rules. Only the 8 first ones which match will be kept. Using this, it is possible to feed multiple tables at once in the hope to increase the chance to recognize a user on another protocol or access method. Using multiple store-response rules with the same table is possible and may be used to find the best criterion to rely on, by arranging the rules by decreasing preference order. Only the first extracted criterion for a given table will be stored. All subsequent store- response rules referencing the same table will be skipped and their ACLs will not be evaluated. However, even if a store-request rule references a table, a store-response rule may also use the same table. This means that each table may learn exactly one element from the request and one element from the response at once. The table will contain the real server that processed the request. Example : # Learn SSL session ID from both request and response and create affinity. backend https mode tcp balance roundrobin # maximum SSL session ID length is 32 bytes. stick-table type binary len 32 size 30k expire 30m acl clienthello req_ssl_hello_type 1 acl serverhello rep_ssl_hello_type 2 # use tcp content accepts to detects ssl client and server hello. tcp-request inspect-delay 5s tcp-request content accept if clienthello # no timeout on response inspect delay by default. tcp-response content accept if serverhello # SSL session ID (SSLID) may be present on a client or server hello. # Its length is coded on 1 byte at offset 43 and its value starts # at offset 44. # Match and learn on request if client hello. stick on payload_lv(43,1) if clienthello # Learn on response if server hello. stick store-response payload_lv(43,1) if serverhello server s1 192.168.1.1:443 server s2 192.168.1.1:443 See also : "stick-table", "stick on", and section 7 about ACLs and pattern extraction. tcp-check connect [params*] Opens a new connection May be used in sections: defaults | frontend | listen | backend no | no | yes | yes When an application lies on more than a single TCP port or when HAProxy load-balance many services in a single backend, it makes sense to probe all the services individually before considering a server as operational. When there are no TCP port configured on the server line neither server port directive, then the 'tcp-check connect port <port>' must be the first step of the sequence. In a tcp-check ruleset a 'connect' is required, it is also mandatory to start the ruleset with a 'connect' rule. Purpose is to ensure admin know what they do. Parameters : They are optional and can be used to describe how HAProxy should open and use the TCP connection. port if not set, check port or server port is used. It tells HAProxy where to open the connection to. <port> must be a valid TCP port source integer, from 1 to 65535. send-proxy send a PROXY protocol string ssl opens a ciphered connection Examples: # check HTTP and HTTPs services on a server. # first open port 80 thanks to server line port directive, then # tcp-check opens port 443, ciphered and run a request on it: option tcp-check tcp-check connect tcp-check send GET\ /\ HTTP/1.0\r\n tcp-check send Host:\ haproxy.1wt.eu\r\n tcp-check send \r\n tcp-check expect rstring (2..|3..) tcp-check connect port 443 ssl tcp-check send GET\ /\ HTTP/1.0\r\n tcp-check send Host:\ haproxy.1wt.eu\r\n tcp-check send \r\n tcp-check expect rstring (2..|3..) server www 10.0.0.1 check port 80 # check both POP and IMAP from a single server: option tcp-check tcp-check connect port 110 tcp-check expect string +OK\ POP3\ ready tcp-check connect port 143 tcp-check expect string *\ OK\ IMAP4\ ready server mail 10.0.0.1 check See also : "option tcp-check", "tcp-check send", "tcp-check expect" tcp-check expect [!] <match> <pattern> Specify data to be collected and analysed during a generic health check May be used in sections: defaults | frontend | listen | backend no | no | yes | yes Arguments : <match> is a keyword indicating how to look for a specific pattern in the response. The keyword may be one of "string", "rstring" or binary. The keyword may be preceded by an exclamation mark ("!") to negate the match. Spaces are allowed between the exclamation mark and the keyword. See below for more details on the supported keywords. <pattern> is the pattern to look for. It may be a string or a regular expression. If the pattern contains spaces, they must be escaped with the usual backslash ('\'). If the match is set to binary, then the pattern must be passed as a serie of hexadecimal digits in an even number. Each sequence of two digits will represent a byte. The hexadecimal digits may be used upper or lower case. The available matches are intentionally similar to their http-check cousins : string <string> : test the exact string matches in the response buffer. A health check response will be considered valid if the response's buffer contains this exact string. If the "string" keyword is prefixed with "!", then the response will be considered invalid if the body contains this string. This can be used to look for a mandatory pattern in a protocol response, or to detect a failure when a specific error appears in a protocol banner. rstring <regex> : test a regular expression on the response buffer. A health check response will be considered valid if the response's buffer matches this expression. If the "rstring" keyword is prefixed with "!", then the response will be considered invalid if the body matches the expression. binary <hexstring> : test the exact string in its hexadecimal form matches in the response buffer. A health check response will be considered valid if the response's buffer contains this exact hexadecimal string. Purpose is to match data on binary protocols. It is important to note that the responses will be limited to a certain size defined by the global "tune.chksize" option, which defaults to 16384 bytes. Thus, too large responses may not contain the mandatory pattern when using "string", "rstring" or binary. If a large response is absolutely required, it is possible to change the default max size by setting the global variable. However, it is worth keeping in mind that parsing very large responses can waste some CPU cycles, especially when regular expressions are used, and that it is always better to focus the checks on smaller resources. Also, in its current state, the check will not find any string nor regex past a null character in the response. Similarly it is not possible to request matching the null character. Examples : # perform a POP check option tcp-check tcp-check expect string +OK\ POP3\ ready # perform an IMAP check option tcp-check tcp-check expect string *\ OK\ IMAP4\ ready # look for the redis master server option tcp-check tcp-check send PING\r\n tcp-check expect +PONG tcp-check send info\ replication\r\n tcp-check expect string role:master tcp-check send QUIT\r\n tcp-check expect string +OK See also : "option tcp-check", "tcp-check connect", "tcp-check send", "tcp-check send-binary", "http-check expect", tune.chksize tcp-check send <data> Specify a string to be sent as a question during a generic health check May be used in sections: defaults | frontend | listen | backend no | no | yes | yes <data> : the data to be sent as a question during a generic health check session. For now, <data> must be a string. Examples : # look for the redis master server option tcp-check tcp-check send info\ replication\r\n tcp-check expect string role:master See also : "option tcp-check", "tcp-check connect", "tcp-check expect", "tcp-check send-binary", tune.chksize tcp-check send-binary <hexastring> Specify an hexa digits string to be sent as a binary question during a raw tcp health check May be used in sections: defaults | frontend | listen | backend no | no | yes | yes <data> : the data to be sent as a question during a generic health check session. For now, <data> must be a string. <hexastring> : test the exact string in its hexadecimal form matches in the response buffer. A health check response will be considered valid if the response's buffer contains this exact hexadecimal string. Purpose is to send binary data to ask on binary protocols. Examples : # redis check in binary option tcp-check tcp-check send-binary 50494e470d0a # PING\r\n tcp-check expect binary 2b504F4e47 # +PONG See also : "option tcp-check", "tcp-check connect", "tcp-check expect", "tcp-check send", tune.chksize tcp-request connection <action> [{if | unless} <condition>] Perform an action on an incoming connection depending on a layer 4 condition May be used in sections : defaults | frontend | listen | backend no | yes | yes | no Arguments : <action> defines the action to perform if the condition applies. Valid actions include : "accept", "reject", "track-sc0", "track-sc1", "track-sc2", and "expect-proxy". See below for more details. <condition> is a standard layer4-only ACL-based condition (see section 7). Immediately after acceptance of a new incoming connection, it is possible to evaluate some conditions to decide whether this connection must be accepted or dropped or have its counters tracked. Those conditions cannot make use of any data contents because the connection has not been read from yet, and the buffers are not yet allocated. This is used to selectively and very quickly accept or drop connections from various sources with a very low overhead. If some contents need to be inspected in order to take the decision, the "tcp-request content" statements must be used instead. The "tcp-request connection" rules are evaluated in their exact declaration order. If no rule matches or if there is no rule, the default action is to accept the incoming connection. There is no specific limit to the number of rules which may be inserted. Five types of actions are supported : - accept : accepts the connection if the condition is true (when used with "if") or false (when used with "unless"). The first such rule executed ends the rules evaluation. - reject : rejects the connection if the condition is true (when used with "if") or false (when used with "unless"). The first such rule executed ends the rules evaluation. Rejected connections do not even become a session, which is why they are accounted separately for in the stats, as "denied connections". They are not considered for the session rate-limit and are not logged either. The reason is that these rules should only be used to filter extremely high connection rates such as the ones encountered during a massive DDoS attack. Under these extreme conditions, the simple action of logging each event would make the system collapse and would considerably lower the filtering capacity. If logging is absolutely desired, then "tcp-request content" rules should be used instead. - expect-proxy layer4 : configures the client-facing connection to receive a PROXY protocol header before any byte is read from the socket. This is equivalent to having the "accept-proxy" keyword on the "bind" line, except that using the TCP rule allows the PROXY protocol to be accepted only for certain IP address ranges using an ACL. This is convenient when multiple layers of load balancers are passed through by traffic coming from public hosts. - capture <sample> len <length> : This only applies to "tcp-request content" rules. It captures sample expression <sample> from the request buffer, and converts it to a string of at most <len> characters. The resulting string is stored into the next request "capture" slot, so it will possibly appear next to some captured HTTP headers. It will then automatically appear in the logs, and it will be possible to extract it using sample fetch rules to feed it into headers or anything. The length should be limited given that this size will be allocated for each capture during the whole session life. Since it applies to Please check section 7.3 (Fetching samples) and "capture request header" for more information. - { track-sc0 | track-sc1 | track-sc2 } <key> [table <table>] : enables tracking of sticky counters from current connection. These rules do not stop evaluation and do not change default action. Two sets of counters may be simultaneously tracked by the same connection. The first "track-sc0" rule executed enables tracking of the counters of the specified table as the first set. The first "track-sc1" rule executed enables tracking of the counters of the specified table as the second set. The first "track-sc2" rule executed enables tracking of the counters of the specified table as the third set. It is a recommended practice to use the first set of counters for the per-frontend counters and the second set for the per-backend ones. But this is just a guideline, all may be used everywhere. These actions take one or two arguments : <key> is mandatory, and is a sample expression rule as described in section 7.3. It describes what elements of the incoming request or connection will be analysed, extracted, combined, and used to select which table entry to update the counters. Note that "tcp-request connection" cannot use content-based fetches. <table> is an optional table to be used instead of the default one, which is the stick-table declared in the current proxy. All the counters for the matches and updates for the key will then be performed in that table until the session ends. Once a "track-sc*" rule is executed, the key is looked up in the table and if it is not found, an entry is allocated for it. Then a pointer to that entry is kept during all the session's life, and this entry's counters are updated as often as possible, every time the session's counters are updated, and also systematically when the session ends. Counters are only updated for events that happen after the tracking has been started. For example, connection counters will not be updated when tracking layer 7 information, since the connection event happens before layer7 information is extracted. If the entry tracks concurrent connection counters, one connection is counted for as long as the entry is tracked, and the entry will not expire during that time. Tracking counters also provides a performance advantage over just checking the keys, because only one table lookup is performed for all ACL checks that make use of it. Note that the "if/unless" condition is optional. If no condition is set on the action, it is simply performed unconditionally. That can be useful for "track-sc*" actions as well as for changing the default action to a reject. Example: accept all connections from white-listed hosts, reject too fast connection without counting them, and track accepted connections. This results in connection rate being capped from abusive sources. tcp-request connection accept if { src -f /etc/haproxy/whitelist.lst } tcp-request connection reject if { src_conn_rate gt 10 } tcp-request connection track-sc0 src Example: accept all connections from white-listed hosts, count all other connections and reject too fast ones. This results in abusive ones being blocked as long as they don't slow down. tcp-request connection accept if { src -f /etc/haproxy/whitelist.lst } tcp-request connection track-sc0 src tcp-request connection reject if { sc0_conn_rate gt 10 } Example: enable the PROXY protocol for traffic coming from all known proxies. tcp-request connection expect-proxy layer4 if { src -f proxies.lst } See section 7 about ACL usage. See also : "tcp-request content", "stick-table" tcp-request content <action> [{if | unless} <condition>] Perform an action on a new session depending on a layer 4-7 condition May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <action> defines the action to perform if the condition applies. Valid actions include : "accept", "reject", "track-sc0", "track-sc1", "track-sc2" and "capture". See "tcp-request connection" above for their signification. <condition> is a standard layer 4-7 ACL-based condition (see section 7). A request's contents can be analysed at an early stage of request processing called "TCP content inspection". During this stage, ACL-based rules are evaluated every time the request contents are updated, until either an "accept" or a "reject" rule matches, or the TCP request inspection delay expires with no matching rule. The first difference between these rules and "tcp-request connection" rules is that "tcp-request content" rules can make use of contents to take a decision. Most often, these decisions will consider a protocol recognition or validity. The second difference is that content-based rules can be used in both frontends and backends. In case of HTTP keep-alive with the client, all tcp-request content rules are evaluated again, so haproxy keeps a record of what sticky counters were assigned by a "tcp-request connection" versus a "tcp-request content" rule, and flushes all the content-related ones after processing an HTTP request, so that they may be evaluated again by the rules being evaluated again for the next request. This is of particular importance when the rule tracks some L7 information or when it is conditioned by an L7-based ACL, since tracking may change between requests. Content-based rules are evaluated in their exact declaration order. If no rule matches or if there is no rule, the default action is to accept the contents. There is no specific limit to the number of rules which may be inserted. Four types of actions are supported : - accept : the request is accepted - reject : the request is rejected and the connection is closed - capture : the specified sample expression is captured - { track-sc0 | track-sc1 | track-sc2 } <key> [table <table>] They have the same meaning as their counter-parts in "tcp-request connection" so please refer to that section for a complete description. While there is nothing mandatory about it, it is recommended to use the track-sc0 in "tcp-request connection" rules, track-sc1 for "tcp-request content" rules in the frontend, and track-sc2 for "tcp-request content" rules in the backend, because that makes the configuration more readable and easier to troubleshoot, but this is just a guideline and all counters may be used everywhere. Note that the "if/unless" condition is optional. If no condition is set on the action, it is simply performed unconditionally. That can be useful for "track-sc*" actions as well as for changing the default action to a reject. It is perfectly possible to match layer 7 contents with "tcp-request content" rules, since HTTP-specific ACL matches are able to preliminarily parse the contents of a buffer before extracting the required data. If the buffered contents do not parse as a valid HTTP message, then the ACL does not match. The parser which is involved there is exactly the same as for all other HTTP processing, so there is no risk of parsing something differently. In an HTTP backend connected to from an HTTP frontend, it is guaranteed that HTTP contents will always be immediately present when the rule is evaluated first. Tracking layer7 information is also possible provided that the information are present when the rule is processed. The rule processing engine is able to wait until the inspect delay expires when the data to be tracked is not yet available. Example: # Accept HTTP requests containing a Host header saying "example.com" # and reject everything else. acl is_host_com hdr(Host) -i example.com tcp-request inspect-delay 30s tcp-request content accept if is_host_com tcp-request content reject Example: # reject SMTP connection if client speaks first tcp-request inspect-delay 30s acl content_present req_len gt 0 tcp-request content reject if content_present # Forward HTTPS connection only if client speaks tcp-request inspect-delay 30s acl content_present req_len gt 0 tcp-request content accept if content_present tcp-request content reject Example: # Track the last IP from X-Forwarded-For tcp-request inspect-delay 10s tcp-request content track-sc0 hdr(x-forwarded-for,-1) Example: # track request counts per "base" (concatenation of Host+URL) tcp-request inspect-delay 10s tcp-request content track-sc0 base table req-rate Example: track per-frontend and per-backend counters, block abusers at the frontend when the backend detects abuse. frontend http # Use General Purpose Couter 0 in SC0 as a global abuse counter # protecting all our sites stick-table type ip size 1m expire 5m store gpc0 tcp-request connection track-sc0 src tcp-request connection reject if { sc0_get_gpc0 gt 0 } ... use_backend http_dynamic if { path_end .php } backend http_dynamic # if a source makes too fast requests to this dynamic site (tracked # by SC1), block it globally in the frontend. stick-table type ip size 1m expire 5m store http_req_rate(10s) acl click_too_fast sc1_http_req_rate gt 10 acl mark_as_abuser sc0_inc_gpc0 gt 0 tcp-request content track-sc1 src tcp-request content reject if click_too_fast mark_as_abuser See section 7 about ACL usage. See also : "tcp-request connection", "tcp-request inspect-delay" tcp-request inspect-delay <timeout> Set the maximum allowed time to wait for data during content inspection May be used in sections : defaults | frontend | listen | backend no | yes | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. People using haproxy primarily as a TCP relay are often worried about the risk of passing any type of protocol to a server without any analysis. In order to be able to analyze the request contents, we must first withhold the data then analyze them. This statement simply enables withholding of data for at most the specified amount of time. TCP content inspection applies very early when a connection reaches a frontend, then very early when the connection is forwarded to a backend. This means that a connection may experience a first delay in the frontend and a second delay in the backend if both have tcp-request rules. Note that when performing content inspection, haproxy will evaluate the whole rules for every new chunk which gets in, taking into account the fact that those data are partial. If no rule matches before the aforementioned delay, a last check is performed upon expiration, this time considering that the contents are definitive. If no delay is set, haproxy will not wait at all and will immediately apply a verdict based on the available information. Obviously this is unlikely to be very useful and might even be racy, so such setups are not recommended. As soon as a rule matches, the request is released and continues as usual. If the timeout is reached and no rule matches, the default policy will be to let it pass through unaffected. For most protocols, it is enough to set it to a few seconds, as most clients send the full request immediately upon connection. Add 3 or more seconds to cover TCP retransmits but that's all. For some protocols, it may make sense to use large values, for instance to ensure that the client never talks before the server (eg: SMTP), or to wait for a client to talk before passing data to the server (eg: SSL). Note that the client timeout must cover at least the inspection delay, otherwise it will expire first. If the client closes the connection or if the buffer is full, the delay immediately expires since the contents will not be able to change anymore. See also : "tcp-request content accept", "tcp-request content reject", "timeout client". tcp-response content <action> [{if | unless} <condition>] Perform an action on a session response depending on a layer 4-7 condition May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <action> defines the action to perform if the condition applies. Valid actions include : "accept", "close", "reject". <condition> is a standard layer 4-7 ACL-based condition (see section 7). Response contents can be analysed at an early stage of response processing called "TCP content inspection". During this stage, ACL-based rules are evaluated every time the response contents are updated, until either an "accept", "close" or a "reject" rule matches, or a TCP response inspection delay is set and expires with no matching rule. Most often, these decisions will consider a protocol recognition or validity. Content-based rules are evaluated in their exact declaration order. If no rule matches or if there is no rule, the default action is to accept the contents. There is no specific limit to the number of rules which may be inserted. Two types of actions are supported : - accept : accepts the response if the condition is true (when used with "if") or false (when used with "unless"). The first such rule executed ends the rules evaluation. - close : immediately closes the connection with the server if the condition is true (when used with "if"), or false (when used with "unless"). The first such rule executed ends the rules evaluation. The main purpose of this action is to force a connection to be finished between a client and a server after an exchange when the application protocol expects some long time outs to elapse first. The goal is to eliminate idle connections which take significant resources on servers with certain protocols. - reject : rejects the response if the condition is true (when used with "if") or false (when used with "unless"). The first such rule executed ends the rules evaluation. Rejected session are immediately closed. Note that the "if/unless" condition is optional. If no condition is set on the action, it is simply performed unconditionally. That can be useful for for changing the default action to a reject. It is perfectly possible to match layer 7 contents with "tcp-response content" rules, but then it is important to ensure that a full response has been buffered, otherwise no contents will match. In order to achieve this, the best solution involves detecting the HTTP protocol during the inspection period. See section 7 about ACL usage. See also : "tcp-request content", "tcp-response inspect-delay" tcp-response inspect-delay <timeout> Set the maximum allowed time to wait for a response during content inspection May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. See also : "tcp-response content", "tcp-request inspect-delay". timeout check <timeout> Set additional check timeout, but only after a connection has been already established. May be used in sections: defaults | frontend | listen | backend yes | no | yes | yes Arguments: <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. If set, haproxy uses min("timeout connect", "inter") as a connect timeout for check and "timeout check" as an additional read timeout. The "min" is used so that people running with *very* long "timeout connect" (eg. those who needed this due to the queue or tarpit) do not slow down their checks. (Please also note that there is no valid reason to have such long connect timeouts, because "timeout queue" and "timeout tarpit" can always be used to avoid that). If "timeout check" is not set haproxy uses "inter" for complete check timeout (connect + read) exactly like all <1.3.15 version. In most cases check request is much simpler and faster to handle than normal requests and people may want to kick out laggy servers so this timeout should be smaller than "timeout server". This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. See also: "timeout connect", "timeout queue", "timeout server", "timeout tarpit". timeout client <timeout> timeout clitimeout <timeout> (deprecated) Set the maximum inactivity time on the client side. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. The inactivity timeout applies when the client is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase, when the client sends the request, and during the response while it is reading data sent by the server. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. It is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). If some long-lived sessions are mixed with short-lived sessions (eg: WebSocket and HTTP), it's worth considering "timeout tunnel", which overrides "timeout client" and "timeout server" for tunnels, as well as "timeout client-fin" for half-closed connections. This parameter is specific to frontends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter replaces the old, deprecated "clitimeout". It is recommended to use it to write new configurations. The form "timeout clitimeout" is provided only by backwards compatibility but its use is strongly discouraged. See also : "clitimeout", "timeout server", "timeout tunnel". timeout client-fin <timeout> Set the inactivity timeout on the client side for half-closed connections. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. The inactivity timeout applies when the client is expected to acknowledge or send data while one direction is already shut down. This timeout is different from "timeout client" in that it only applies to connections which are closed in one direction. This is particularly useful to avoid keeping connections in FIN_WAIT state for too long when clients do not disconnect cleanly. This problem is particularly common long connections such as RDP or WebSocket. Note that this timeout can override "timeout tunnel" when a connection shuts down in one direction. This parameter is specific to frontends, but can be specified once for all in "defaults" sections. By default it is not set, so half-closed connections will use the other timeouts (timeout.client or timeout.tunnel). See also : "timeout client", "timeout server-fin", and "timeout tunnel". timeout connect <timeout> timeout contimeout <timeout> (deprecated) Set the maximum time to wait for a connection attempt to a server to succeed. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. If the server is located on the same LAN as haproxy, the connection should be immediate (less than a few milliseconds). Anyway, it is a good practice to cover one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds). By default, the connect timeout also presets both queue and tarpit timeouts to the same value if these have not been specified. This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of failed sessions in the system if the system's timeouts are not configured either. This parameter replaces the old, deprecated "contimeout". It is recommended to use it to write new configurations. The form "timeout contimeout" is provided only by backwards compatibility but its use is strongly discouraged. See also: "timeout check", "timeout queue", "timeout server", "contimeout", "timeout tarpit". timeout http-keep-alive <timeout> Set the maximum allowed time to wait for a new HTTP request to appear May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. By default, the time to wait for a new request in case of keep-alive is set by "timeout http-request". However this is not always convenient because some people want very short keep-alive timeouts in order to release connections faster, and others prefer to have larger ones but still have short timeouts once the request has started to present itself. The "http-keep-alive" timeout covers these needs. It will define how long to wait for a new HTTP request to start coming after a response was sent. Once the first byte of request has been seen, the "http-request" timeout is used to wait for the complete request to come. Note that empty lines prior to a new request do not refresh the timeout and are not counted as a new request. There is also another difference between the two timeouts : when a connection expires during timeout http-keep-alive, no error is returned, the connection just closes. If the connection expires in "http-request" while waiting for a connection to complete, a HTTP 408 error is returned. In general it is optimal to set this value to a few tens to hundreds of milliseconds, to allow users to fetch all objects of a page at once but without waiting for further clicks. Also, if set to a very small value (eg: 1 millisecond) it will probably only accept pipelined requests but not the non-pipelined ones. It may be a nice trade-off for very large sites running with tens to hundreds of thousands of clients. If this parameter is not set, the "http-request" timeout applies, and if both are not set, "timeout client" still applies at the lower level. It should be set in the frontend to take effect, unless the frontend is in TCP mode, in which case the HTTP backend's timeout will be used. See also : "timeout http-request", "timeout client". timeout http-request <timeout> Set the maximum allowed time to wait for a complete HTTP request May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. In order to offer DoS protection, it may be required to lower the maximum accepted time to receive a complete HTTP request without affecting the client timeout. This helps protecting against established connections on which nothing is sent. The client timeout cannot offer a good protection against this abuse because it is an inactivity timeout, which means that if the attacker sends one character every now and then, the timeout will not trigger. With the HTTP request timeout, no matter what speed the client types, the request will be aborted if it does not complete in time. When the timeout expires, an HTTP 408 response is sent to the client to inform it about the problem, and the connection is closed. The logs will report termination codes "cR". Some recent browsers are having problems with this standard, well-documented behaviour, so it might be needed to hide the 408 code using "option http-ignore-probes" or "errorfile 408 /dev/null". See more details in the explanations of the "cR" termination code in section 8.5. Note that this timeout only applies to the header part of the request, and not to any data. As soon as the empty line is received, this timeout is not used anymore. It is used again on keep-alive connections to wait for a second request if "timeout http-keep-alive" is not set. Generally it is enough to set it to a few seconds, as most clients send the full request immediately upon connection. Add 3 or more seconds to cover TCP retransmits but that's all. Setting it to very low values (eg: 50 ms) will generally work on local networks as long as there are no packet losses. This will prevent people from sending bare HTTP requests using telnet. If this parameter is not set, the client timeout still applies between each chunk of the incoming request. It should be set in the frontend to take effect, unless the frontend is in TCP mode, in which case the HTTP backend's timeout will be used. See also : "errorfile", "http-ignore-probes", "timeout http-keep-alive", and "timeout client". timeout queue <timeout> Set the maximum time to wait in the queue for a connection slot to be free May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. When a server's maxconn is reached, connections are left pending in a queue which may be server-specific or global to the backend. In order not to wait indefinitely, a timeout is applied to requests pending in the queue. If the timeout is reached, it is considered that the request will almost never be served, so it is dropped and a 503 error is returned to the client. The "timeout queue" statement allows to fix the maximum time for a request to be left pending in a queue. If unspecified, the same value as the backend's connection timeout ("timeout connect") is used, for backwards compatibility with older versions with no "timeout queue" parameter. See also : "timeout connect", "contimeout". timeout server <timeout> timeout srvtimeout <timeout> (deprecated) Set the maximum inactivity time on the server side. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. The inactivity timeout applies when the server is expected to acknowledge or send data. In HTTP mode, this timeout is particularly important to consider during the first phase of the server's response, when it has to send the headers, as it directly represents the server's processing time for the request. To find out what value to put there, it's often good to start with what would be considered as unacceptable response times, then check the logs to observe the response time distribution, and adjust the value accordingly. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly recommended that the client timeout remains equal to the server timeout in order to avoid complex situations to debug. Whatever the expected server response times, it is a good practice to cover at least one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds minimum). If some long-lived sessions are mixed with short-lived sessions (eg: WebSocket and HTTP), it's worth considering "timeout tunnel", which overrides "timeout client" and "timeout server" for tunnels. This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. An unspecified timeout results in an infinite timeout, which is not recommended. Such a usage is accepted and works but reports a warning during startup because it may results in accumulation of expired sessions in the system if the system's timeouts are not configured either. This parameter replaces the old, deprecated "srvtimeout". It is recommended to use it to write new configurations. The form "timeout srvtimeout" is provided only by backwards compatibility but its use is strongly discouraged. See also : "srvtimeout", "timeout client" and "timeout tunnel". timeout server-fin <timeout> Set the inactivity timeout on the server side for half-closed connections. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. The inactivity timeout applies when the server is expected to acknowledge or send data while one direction is already shut down. This timeout is different from "timeout server" in that it only applies to connections which are closed in one direction. This is particularly useful to avoid keeping connections in FIN_WAIT state for too long when a remote server does not disconnect cleanly. This problem is particularly common long connections such as RDP or WebSocket. Note that this timeout can override "timeout tunnel" when a connection shuts down in one direction. This setting was provided for completeness, but in most situations, it should not be needed. This parameter is specific to backends, but can be specified once for all in "defaults" sections. By default it is not set, so half-closed connections will use the other timeouts (timeout.server or timeout.tunnel). See also : "timeout client-fin", "timeout server", and "timeout tunnel". timeout tarpit <timeout> Set the duration for which tarpitted connections will be maintained May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes Arguments : <timeout> is the tarpit duration specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. When a connection is tarpitted using "reqtarpit", it is maintained open with no activity for a certain amount of time, then closed. "timeout tarpit" defines how long it will be maintained open. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. If unspecified, the same value as the backend's connection timeout ("timeout connect") is used, for backwards compatibility with older versions with no "timeout tarpit" parameter. See also : "timeout connect", "contimeout". timeout tunnel <timeout> Set the maximum inactivity time on the client and server side for tunnels. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : <timeout> is the timeout value specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as explained at the top of this document. The tunnel timeout applies when a bidirectional connection is established between a client and a server, and the connection remains inactive in both directions. This timeout supersedes both the client and server timeouts once the connection becomes a tunnel. In TCP, this timeout is used as soon as no analyser remains attached to either connection (eg: tcp content rules are accepted). In HTTP, this timeout is used when a connection is upgraded (eg: when switching to the WebSocket protocol, or forwarding a CONNECT request to a proxy), or after the first response when no keepalive/close option is specified. Since this timeout is usually used in conjunction with long-lived connections, it usually is a good idea to also set "timeout client-fin" to handle the situation where a client suddenly disappears from the net and does not acknowledge a close, or sends a shutdown and does not acknowledge pending data anymore. This can happen in lossy networks where firewalls are present, and is detected by the presence of large amounts of sessions in a FIN_WAIT state. The value is specified in milliseconds by default, but can be in any other unit if the number is suffixed by the unit, as specified at the top of this document. Whatever the expected normal idle time, it is a good practice to cover at least one or several TCP packet losses by specifying timeouts that are slightly above multiples of 3 seconds (eg: 4 or 5 seconds minimum). This parameter is specific to backends, but can be specified once for all in "defaults" sections. This is in fact one of the easiest solutions not to forget about it. Example : defaults http option http-server-close timeout connect 5s timeout client 30s timeout client-fin 30s timeout server 30s timeout tunnel 1h # timeout to use with WebSocket and CONNECT See also : "timeout client", "timeout client-fin", "timeout server". transparent (deprecated) Enable client-side transparent proxying May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none This keyword was introduced in order to provide layer 7 persistence to layer 3 load balancers. The idea is to use the OS's ability to redirect an incoming connection for a remote address to a local process (here HAProxy), and let this process know what address was initially requested. When this option is used, sessions without cookies will be forwarded to the original destination IP address of the incoming request (which should match that of another equipment), while requests with cookies will still be forwarded to the appropriate server. The "transparent" keyword is deprecated, use "option transparent" instead. Note that contrary to a common belief, this option does NOT make HAProxy present the client's IP to the server when establishing the connection. See also: "option transparent" unique-id-format <string> Generate a unique ID for each request. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <string> is a log-format string. This keyword creates a ID for each request using the custom log format. A unique ID is useful to trace a request passing through many components of a complex infrastructure. The newly created ID may also be logged using the %ID tag the log-format string. The format should be composed from elements that are guaranteed to be unique when combined together. For instance, if multiple haproxy instances are involved, it might be important to include the node name. It is often needed to log the incoming connection's source and destination addresses and ports. Note that since multiple requests may be performed over the same connection, including a request counter may help differentiate them. Similarly, a timestamp may protect against a rollover of the counter. Logging the process ID will avoid collisions after a service restart. It is recommended to use hexadecimal notation for many fields since it makes them more compact and saves space in logs. Example: unique-id-format %{+X}o\ %ci:%cp_%fi:%fp_%Ts_%rt:%pid will generate: 7F000001:8296_7F00001E:1F90_4F7B0A69_0003:790A See also: "unique-id-header" unique-id-header <name> Add a unique ID header in the HTTP request. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | no Arguments : <name> is the name of the header. Add a unique-id header in the HTTP request sent to the server, using the unique-id-format. It can't work if the unique-id-format doesn't exist. Example: unique-id-format %{+X}o\ %ci:%cp_%fi:%fp_%Ts_%rt:%pid unique-id-header X-Unique-ID will generate: X-Unique-ID: 7F000001:8296_7F00001E:1F90_4F7B0A69_0003:790A See also: "unique-id-format" use_backend <backend> [{if | unless} <condition>] Switch to a specific backend if/unless an ACL-based condition is matched. May be used in sections : defaults | frontend | listen | backend no | yes | yes | no Arguments : <backend> is the name of a valid backend or "listen" section, or a "log-format" string resolving to a backend name. <condition> is a condition composed of ACLs, as described in section 7. If it is omitted, the rule is unconditionally applied. When doing content-switching, connections arrive on a frontend and are then dispatched to various backends depending on a number of conditions. The relation between the conditions and the backends is described with the "use_backend" keyword. While it is normally used with HTTP processing, it can also be used in pure TCP, either without content using stateless ACLs (eg: source address validation) or combined with a "tcp-request" rule to wait for some payload. There may be as many "use_backend" rules as desired. All of these rules are evaluated in their declaration order, and the first one which matches will assign the backend. In the first form, the backend will be used if the condition is met. In the second form, the backend will be used if the condition is not met. If no condition is valid, the backend defined with "default_backend" will be used. If no default backend is defined, either the servers in the same section are used (in case of a "listen" section) or, in case of a frontend, no server is used and a 503 service unavailable response is returned. Note that it is possible to switch from a TCP frontend to an HTTP backend. In this case, either the frontend has already checked that the protocol is HTTP, and backend processing will immediately follow, or the backend will wait for a complete HTTP request to get in. This feature is useful when a frontend must decode several protocols on a unique port, one of them being HTTP. When <backend> is a simple name, it is resolved at configuration time, and an error is reported if the specified backend does not exist. If <backend> is a log-format string instead, no check may be done at configuration time, so the backend name is resolved dynamically at run time. If the resulting backend name does not correspond to any valid backend, no other rule is evaluated, and the default_backend directive is applied instead. Note that when using dynamic backend names, it is highly recommended to use a prefix that no other backend uses in order to ensure that an unauthorized backend cannot be forced from the request. It is worth mentioning that "use_backend" rules with an explicit name are used to detect the association between frontends and backends to compute the backend's "fullconn" setting. This cannot be done for dynamic names. See also: "default_backend", "tcp-request", "fullconn", "log-format", and section 7 about ACLs. use-server <server> if <condition> use-server <server> unless <condition> Only use a specific server if/unless an ACL-based condition is matched. May be used in sections : defaults | frontend | listen | backend no | no | yes | yes Arguments : <server> is the name of a valid server in the same backend section. <condition> is a condition composed of ACLs, as described in section 7. By default, connections which arrive to a backend are load-balanced across the available servers according to the configured algorithm, unless a persistence mechanism such as a cookie is used and found in the request. Sometimes it is desirable to forward a particular request to a specific server without having to declare a dedicated backend for this server. This can be achieved using the "use-server" rules. These rules are evaluated after the "redirect" rules and before evaluating cookies, and they have precedence on them. There may be as many "use-server" rules as desired. All of these rules are evaluated in their declaration order, and the first one which matches will assign the server. If a rule designates a server which is down, and "option persist" is not used and no force-persist rule was validated, it is ignored and evaluation goes on with the next rules until one matches. In the first form, the server will be used if the condition is met. In the second form, the server will be used if the condition is not met. If no condition is valid, the processing continues and the server will be assigned according to other persistence mechanisms. Note that even if a rule is matched, cookie processing is still performed but does not assign the server. This allows prefixed cookies to have their prefix stripped. The "use-server" statement works both in HTTP and TCP mode. This makes it suitable for use with content-based inspection. For instance, a server could be selected in a farm according to the TLS SNI field. And if these servers have their weight set to zero, they will not be used for other traffic. Example : # intercept incoming TLS requests based on the SNI field use-server www if { req_ssl_sni -i www.example.com } server www 192.168.0.1:443 weight 0 use-server mail if { req_ssl_sni -i mail.example.com } server mail 192.168.0.1:587 weight 0 use-server imap if { req_ssl_sni -i imap.example.com } server mail 192.168.0.1:993 weight 0 # all the rest is forwarded to this server server default 192.168.0.2:443 check See also: "use_backend", section 5 about server and section 7 about ACLs.