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. 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 - 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 id - X X X ignore-persist - X X X log X 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-pretend-keepalive (*) X X X X option http-server-close (*) 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 independant-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 nolinger (*) X X X X option originalto X X X X option persist (*) X - X X option redispatch (*) 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-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-table - - X X tcp-request content accept - X X - tcp-request content reject - X X - tcp-request inspect-delay - X X - timeout check X - X X timeout client 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 srvtimeout (deprecated) X - X X timeout tarpit X X X X transparent (deprecated) X - X X use_backend - 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. Example : appsession JSESSIONID len 52 timeout 3h See also : "cookie", "capture cookie", "balance", "stick", "stick-table" and "ignore-persist" 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 [<max_wait>]] 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 4128 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. 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 The left part of the URI (before the question mark) is hashed and divided by the total weight of the running servers. The result designates which server will receive the request. This ensures that a 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 support 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 the question mark indicating a query string ('?') is not present in the URL. Optionally, specify a number of octets to wait for before attempting to search the message body. If the entity can not be searched, then round robin is used for each request. For instance, if your clients always send the LB parameter in the first 128 bytes, then specify that. The default is 48. The entity data will not be scanned until the required number of octets have arrived at the gateway, this is the minimum of: (default/max_wait, Content-Length or first chunk length). If Content-Length is missing or zero, it does not need to wait for more data than the client promised to send. When Content-Length is present and larger than <max_wait>, then waiting is limited to <max_wait> and it is assumed that this will be enough data to search for the presence of the parameter. In the unlikely event that Transfer-Encoding: chunked is used, only the first chunk is scanned. Parameter values separated by a chunk boundary, may be randomly balanced if at all. 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". <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. balance uri [len <len>] [depth <depth>] balance url_param <param> [check_post [<max_wait>]] 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> [, ...] bind [<address>]:<port_range> [, ...] interface <interface> bind [<address>]:<port_range> [, ...] mss <maxseg> bind [<address>]:<port_range> [, ...] transparent bind [<address>]:<port_range> [, ...] id <id> bind [<address>]:<port_range> [, ...] name <name> bind [<address>]:<port_range> [, ...] defer-accept 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". <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. 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 independant of the 'uid' parameter. <interface> is an optional physical interface name. This is currently only supported on Linux. The interface must be a physical interface, not an aliased interface. When specified, all addresses on the same line will only be accepted if the incoming packet physically come through the designated interface. It is also possible to bind multiple frontends to the same address if they are bound to different interfaces. Note that binding to a physical interface requires root privileges. <maxseg> is an optional TCP Maximum Segment Size (MSS) value to be advertised on incoming connections. This can be used to force a lower MSS for certain specific ports, for instance for connections passing through a VPN. Note that this relies on a kernel feature which is theorically supported under Linux but was buggy in all versions prior to 2.6.28. It may or may not work on other operating systems. The commonly advertised value on Ethernet networks is 1460 = 1500(MTU) - 40(IP+TCP). <id> is a persistent value for socket ID. Must be positive and unique in the proxy. An unused value will automatically be assigned if unset. Can only be used when defining only a single socket. <name> is an optional name provided for stats transparent is an optional keyword which is supported only on certain Linux kernels. It indicates that the addresses will be bound even if they do not belong to the local machine. Any packet targeting any of these addresses will be caught just as if the address was locally configured. This normally requires that IP forwarding is enabled. Caution! do not use this with the default address '*', as it would redirect any traffic for the specified port. This keyword is available only when HAProxy is built with USE_LINUX_TPROXY=1. defer-accept is an optional keyword which is supported only on certain Linux kernels. It states that a connection will only be accepted once some data arrive on it, or at worst after the first retransmit. This should be used only on protocols for which the client talks first (eg: HTTP). It can slightly improve performance by ensuring that most of the request is already available when the connection is accepted. On the other hand, it will not be able to detect connections which don't talk. It is important to note that this option is broken in all kernels up to 2.6.31, as the connection is never accepted until the client talks. This can cause issues with front firewalls which would see an established connection while the proxy will only see it in SYN_RECV. 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 See also : "source". bind-process [ all | odd | even | <number 1-32> ] ... 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,...31. This option may be combined with other numbers. even This instance will be enabled on processes 2,4,6,...32. 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, between 1 and 32. You must be careful not to reference a process number greater than the configured global.nbproc, otherwise some instances might be missing from all processes. 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 processes using this keyword, but this should be more than enough for most setups. Please note that 'all' really means all processes and is not limited to the first 32. 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 See also : "nbproc" in global section. 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 sensible 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 configured in the sources by default to 64 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 first 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>. Only the first 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, but each capture is limited to 64 characters. 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 first 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>. Only the first 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, but each capture is limited to 64 characters. 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". 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 ] [ 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". 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. 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. 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" 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 : none <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 "disabled" 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 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. 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 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 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. 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. 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. 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> Specify a method to use for mapping hashes to servers May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : 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 algorithm for caches. However, due to its principle, the algorithm 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 same IDs. The default hash type is "map-based" and is recommended for most usages. 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 reponse contents or specific status codes 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 "status", "rstatus", "string", or "rstring". The keyword may be preceeded 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 respose 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 respose 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 respose 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 respose 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. 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-request expect status 200 # consider SQL errors as errors http-request expect ! string SQL\ Error # consider status 5xx only as errors http-request expect ! rstatus ^5 # check that we have a correct hexadecimal tag before /html http-request 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 | auth [realm <realm>] } [ { if | unless } <condition> ] Access control for Layer 7 requests May be used in sections: defaults | frontend | listen | backend no | yes | yes | yes These set of options allow to fine control access to a frontend/listen/backend. 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. 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 See also : "stats http-request", section 3.4 about userlists and section 7 about ACL usage. 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 oftenly 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> <facility> [<level> [<minlevel>]] Enable per-instance logging of events and traffic. May be used in sections : defaults | frontend | listen | backend yes | yes | yes | yes 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). - 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). <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 Note that up to two "log" entries may be specified per instance. However, if "log global" is used and if the "global" section already contains 2 log entries, then additional log entries will be ignored. Also, 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 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. 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. Nothing will be logged. 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. 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" 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. 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. Right now, it is not possible to set failure conditions on requests caught 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 RFC2616 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 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. 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 RFC2616 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 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 requests 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 sensible 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. 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", "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. This option implicitly enables the "httpclose" option. Note that this option also enables the parsing of the full request and response, which means we can close the connection to the server very quickly, releasing some resources earlier than with 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. 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> ] 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. 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. It is important to note that as long as HAProxy does not support keep-alive connections, only the first request of a connection will receive the header. For this reason, it is important to ensure that "option httpclose" is set when using this option. 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-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 compbined 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" and "option http-server-close" 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, when a client communicates with a server, HAProxy will only analyze, log, and process the first request of each connection. 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 is worth noting that "option forceclose" has precedence over "option http-server-close" and that combining "http-server-close" with "httpclose" basically achieve the same result as "forceclose". 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" 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", "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, when a client communicates with a server, HAProxy will only analyze, log, and process the first request of each connection. If "option httpclose" is set, it will 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. It seldom happens that some servers incorrectly ignore this header and do not close the connection eventhough 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. If "option forceclose" is specified too, it has precedence over "httpclose". If "option http-server-close" is enabled at the same time as "httpclose", it basically achieves the same result as "option forceclose". 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. 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. 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 http_close" 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 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 oftenly 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 : "option force-persist", "cookie", and section 7 about ACL usage. option independant-streams no option independant-streams Enable or disable independant 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. See also : "timeout client" and "timeout server" 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 May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : none Enable health checks logging so it possible to check for example what was happening before a server crash. Failed health check are logged if server is UP and succeeded health checks if server is DOWN, so the amount of additional information is limited. If health check logging is enabled no health check status is printed when servers is set up UP/DOWN/ENABLED/DISABLED. See also: "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> ] Use MySQL health checks for server testing May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes Arguments : user <username> This is the username which will be used when connecting to MySQL server. 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 >=4.0, 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. It is important to note that as long as HAProxy does not support keep-alive connections, only the first request of a connection will receive the header. For this reason, it is important to ensure that "option httpclose" is set when using this option. 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 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 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 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 user 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 user 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. See also: "option httpchk" 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 "usersrc" 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" and the "req_rdp_cookie" ACL. 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 appears as "FULL" in the statistics, exactly as when it is saturated. See also : the "backlog" keyword and the "fe_sess_rate" ACL criterion. redirect location <to> [code <code>] <option> [{if | unless} <condition>] redirect prefix <to> [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 : <to> With "redirect location", the exact value in <to> is placed into the HTTP "Location" header. In case of "redirect prefix", the "Location" header is built from the concatenation of <to> and the complete URI, including the query string, unless the "drop-query" option is specified (see below). As a special case, if <to> equals exactly "/" in prefix mode, then nothing is inserted before the original URI. It allows one to redirect to the same URL. <code> The code is optional. It indicates which type of HTTP redirection is desired. Only codes 301, 302 and 303 are supported, and 302 is used 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. <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 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", 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 sensible 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 reqidel ^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. <address> is the IPv4 address of the server. Alternatively, a resolvable hostname is supported, but this name will be resolved during start-up. If no address is specified in front of the port, or if address "0.0.0.0" is specified, then the address used will be the same as the one used by the incoming connection. This makes it possible to relay connections for many IPs on a different port or to perform transparent forwarding with connection limitation. <ports> 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 See also: "default-server" 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. <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 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 specificy 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 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 | no | 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. Currently, there are 2 known limitations : - The POST data are limited to one packet, 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. - Expect: 100-continue is not supported. 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", 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 | no | 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 sensible 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 | no | 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 | no | 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 | no | 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 | no | 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 | no | 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 [ <description> ] Enable reporting of a description on the statistics page. May be used in sections : defaults | frontend | listen | backend yes | no | yes | yes <name> 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. 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 informations 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. 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 | no | 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. 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 | no | 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 pattern extraction rule as described in section 7.8. 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. 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", and section 7 about ACLs and pattern extraction. 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. 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" and "stick store-request" 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 pattern extraction rule as described in section 7.8. 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. 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. 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", and section 7 about ACLs and pattern extraction. stick-table type {ip | integer | string [len <length>] } size <size> [expire <expire>] [nopurge] Configure the stickiness table for the current backend May be used in sections : defaults | frontend | listen | backend no | no | 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. 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 31 characters. <length> is the maximum number of characters that will be stored in a "string" type table. See type "string" above. 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). <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. The is only one stick-table per backend. At the moment of writing this doc, it does not seem useful to have multiple tables per backend. 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. See also : "stick match", "stick on", "stick store-request", and section 2.2 about time format. tcp-request content accept [{if | unless} <condition>] Accept a connection if/unless a content inspection condition is matched May be used in sections : defaults | frontend | listen | backend no | yes | yes | no During TCP content inspection, the connection is immediately validated if the condition is true (when used with "if") or false (when used with "unless"). Most of the time during content inspection, a condition will be in an uncertain state which is neither true nor false. The evaluation immediately stops when such a condition is encountered. It is important to understand that "accept" and "reject" rules are evaluated in their exact declaration order, so that it is possible to build complex rules from them. There is no specific limit to the number of rules which may be inserted. Note that the "if/unless" condition is optional. If no condition is set on the action, it is simply performed unconditionally. If no "tcp-request content" rules are matched, the default action already is "accept". Thus, this statement alone does not bring anything without another "reject" statement. See section 7 about ACL usage. See also : "tcp-request content reject", "tcp-request inspect-delay" tcp-request content reject [{if | unless} <condition>] Reject a connection if/unless a content inspection condition is matched May be used in sections : defaults | frontend | listen | backend no | yes | yes | no During TCP content inspection, the connection is immediately rejected if the condition is true (when used with "if") or false (when used with "unless"). Most of the time during content inspection, a condition will be in an uncertain state which is neither true nor false. The evaluation immediately stops when such a condition is encountered. It is important to understand that "accept" and "reject" rules are evaluated in their exact declaration order, so that it is possible to build complex rules from them. There is no specific limit to the number of rules which may be inserted. Note that the "if/unless" condition is optional. If no condition is set on the action, it is simply performed unconditionally. If no "tcp-request content" rules are matched, the default action is set to "accept". Example: # reject SMTP connection if client speaks first tcp-request inspect-delay 30s acl content_present req_len gt 0 tcp-request 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 accept if content_present tcp-request reject See section 7 about ACL usage. See also : "tcp-request content accept", "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 | 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. 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. 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". 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). 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 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. 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 : "timeout http-keep-alive", "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). 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". 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". 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" use_backend <backend> if <condition> use_backend <backend> 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. <condition> is a condition composed of ACLs, as described in section 7. 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. See also: "default_backend", "tcp-request", and section 7 about ACLs.