From c0edfc281e210fbe7e5c3517ae43779be6d0a68f Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Tue, 13 Oct 2015 16:34:46 +0200 Subject: [PATCH] DOC: remove haproxy-{en,fr}.txt This long-awaited moment finally came! --- doc/haproxy-en.txt | 2827 ------------------------------------------- doc/haproxy-fr.txt | 2891 -------------------------------------------- 2 files changed, 5718 deletions(-) delete mode 100644 doc/haproxy-en.txt delete mode 100644 doc/haproxy-fr.txt diff --git a/doc/haproxy-en.txt b/doc/haproxy-en.txt deleted file mode 100644 index 4c673d351..000000000 --- a/doc/haproxy-en.txt +++ /dev/null @@ -1,2827 +0,0 @@ - ------------------- - HAProxy - Reference Manual - ------------------- - version 1.3.15 - willy tarreau - 2008/04/19 - - - !!!! NOTE: THIS DOCUMENT IS OUTDATED !!!! - - Please use "configuration.txt" from the same directory, or download - an up-to-date version from the following location : - - http://haproxy.1wt.eu/download/1.4/doc/configuration.txt - - -============ -| Abstract | -============ - -HAProxy is a TCP/HTTP reverse proxy which is particularly suited for high -availability environments. Indeed, it can : - - route HTTP requests depending on statically assigned cookies ; - - spread the load among several servers while assuring server persistence - through the use of HTTP cookies ; - - switch to backup servers in the event a main one fails ; - - accept connections to special ports dedicated to service monitoring ; - - stop accepting connections without breaking existing ones ; - - add/modify/delete HTTP headers both ways ; - - block requests matching a particular pattern ; - - hold clients to the right application server depending on application - cookies - - report detailed status as HTML pages to authenticated users from an URI - intercepted from the application. - -It needs very little resource. Its event-driven architecture allows it to easily -handle thousands of simultaneous connections on hundreds of instances without -risking the system's stability. - -==================== -| Start parameters | -==================== - -There are only a few command line options : - - -f - -n - = 'maxconn' in 'global' section - -N - = 'maxconn' in 'listen' or 'default' sections - -d starts in foregreound with debugging mode enabled - -D starts in daemon mode - -Ds starts in systemd daemon mode - -q disable messages on output - -V displays messages on output even when -q or 'quiet' are specified. - -c only checks config file and exits with code 0 if no error was found, or - exits with code 1 if a syntax error was found. - -p asks the process to write down each of its children's - pids to this file in daemon mode. - -sf specifies a list of pids to send a FINISH signal to after startup. - -st specifies a list of pids to send a TERMINATE signal to after startup. - -s shows statistics (only if compiled in) - -l shows even more statistics (implies '-s') - -dk disables use of kqueue() - -de disables use of epoll() - -dp disables use of poll() - -db disables background mode (stays in foreground, useful for debugging) - -m enforces a memory usage limit to a maximum of megabytes. - -The maximal number of connections per proxy instance is used as the default -parameter for each instance for which the 'maxconn' paramter is not set in the -'listen' section. - -The maximal number of total connections limits the number of connections used by -the whole process if the 'maxconn' parameter is not set in the 'global' section. - -The debugging mode has the same effect as the 'debug' option in the 'global' -section. When the proxy runs in this mode, it dumps every connections, -disconnections, timestamps, and HTTP headers to stdout. This should NEVER -be used in an init script since it will prevent the system from starting up. - -For debugging, the '-db' option is very useful as it temporarily disables -daemon mode and multi-process mode. The service can then be stopped by simply -pressing Ctrl-C, without having to edit the config nor run full debug. - -Statistics are only available if compiled in with the 'STATTIME' option. It's -only used during code optimization phases, and will soon disappear. - -The '-st' and '-sf' options are used for hot reconfiguration (see below). - -====================== -| Configuration file | -====================== - -Structure -========= - -The configuration file parser ignores empty lines, spaces, tabs. Anything -between a sharp ('#') not following a backslash ('\'), and the end of a line -constitutes a comment and is ignored too. - -The configuration file is segmented in sections. A section begins whenever -one of these 3 keywords are encountered : - - - 'global' - - 'listen' - - 'defaults' - -Every parameter refer to the section beginning at the last one of these 3 -keywords. - - -1) Global parameters -==================== - -Global parameters affect the whole process behaviour. They are all set in the -'global' section. There may be several 'global' sections if needed, but their -parameters will only be merged. Allowed parameters in 'global' section include -the following ones : - - - log
[max_level] - - maxconn - - uid - - gid - - user - - group - - chroot - - nbproc - - daemon - - debug - - nokqueue - - noepoll - - nopoll - - quiet - - pidfile - - ulimit-n - - stats - - tune.maxpollevents - - -1.1) Event logging ------------------- -Most events are logged : start, stop, servers going up and down, connections and -errors. Each event generates a syslog message which can be sent to up to 2 -servers. The syntax is : - - log [max_level] - -Connections are logged at level "info". Services initialization and servers -going up are logged at level "notice", termination signals are logged at -"warning", and definitive service termination, as well as loss of servers are -logged at level "alert". The optional parameter specifies above -what level messages should be sent. Level can take one of these 8 values : - - emerg, alert, crit, err, warning, notice, info, debug - -For backwards compatibility with versions 1.1.16 and earlier, the default level -value is "debug" if not specified. - -Permitted facilities are : - kern, user, mail, daemon, auth, syslog, lpr, news, - uucp, cron, auth2, ftp, ntp, audit, alert, cron2, - local0, local1, local2, local3, local4, local5, local6, local7 - -According to RFC3164, messages are truncated to 1024 bytes before being emitted. - -Example : ---------- - global - log 192.168.2.200 local3 - log 127.0.0.1 local4 notice - - -1.2) limiting the number of connections ---------------------------------------- -It is possible and recommended to limit the global number of per-process -connections using the 'maxconn' global keyword. Since one connection includes -both a client and a server, it means that the max number of TCP sessions will -be about the double of this number. It's important to understand this when -trying to find best values for 'ulimit -n' before starting the proxy. To -anticipate the number of sockets needed, all these parameters must be counted : - - - 1 socket per incoming connection - - 1 socket per outgoing connection - - 1 socket per address/port/proxy tuple. - - 1 socket per server being health-checked - - 1 socket for all logs - -In simple configurations where each proxy only listens one one address/port, -set the limit of file descriptors (ulimit -n) to -(2 * maxconn + nbproxies + nbservers + 1). Starting with versions 1.1.32/1.2.6, -it is now possible to set the limit in the configuration using the 'ulimit-n' -global keyword, provided the proxy is started as root. This puts an end to the -recurrent problem of ensuring that the system limits are adapted to the proxy -values. Note that these limits are per-process. - -Example : ---------- - global - maxconn 32000 - ulimit-n 65536 - - -1.3) Drop of priviledges ------------------------- -In order to reduce the risk and consequences of attacks, in the event where a -yet non-identified vulnerability would be successfully exploited, it's possible -to lower the process priviledges and even isolate it in a riskless directory. - -In the 'global' section, the 'uid' parameter sets a numerical user identifier -which the process will switch to after binding its listening sockets. The value -'0', which normally represents the super-user, here indicates that the UID must -not change during startup. It's the default behaviour. The 'gid' parameter does -the same for the group identifier. If setting an uid is not possible because of -deployment constraints, it is possible to set a user name with the 'user' -keyword followed by a valid user name. The same is true for the gid. It is -possible to specify a group name after the 'group' keyword. - -It is particularly advised against use of generic accounts such as 'nobody' -because it has the same consequences as using 'root' if other services use -them. - -The 'chroot' parameter makes the process isolate itself in an empty directory -just before switching its UID. This type of isolation (chroot) can sometimes -be worked around on certain OS (Linux, Solaris), provided that the attacker -has gained 'root' priviledges and has the ability to use or create a directory. -For this reason, it's capital to use a dedicated directory and not to share one -between several services of different nature. To make isolation more resistant, -it's recommended to use an empty directory without any right, and to change the -UID of the process so that it cannot do anything there. - -Note: in the event where such a vulnerability would be exploited, it's most -likely that first attempts would kill the process due to 'Segmentation Fault', -'Bus Error' or 'Illegal Instruction' signals. Eventhough it's true that -isolating the server reduces the risks of intrusion, it's sometimes useful to -find why a process dies, via the analysis of a 'core' file, although very rare -(the last bug of this sort was fixed in 1.1.9). For security reasons, most -systems disable the generation of core file when a process changes its UID. So -the two workarounds are either to start the process from a restricted user -account, which will not be able to chroot itself, or start it as root and not -change the UID. In both cases the core will be either in the start or the chroot -directories. Do not forget to allow core dumps prior to start the process : - -# ulimit -c unlimited - -Example : ---------- - - # with uid/gid - global - uid 30000 - gid 30000 - chroot /var/chroot/haproxy - - # with user/group - global - user haproxy - group public - chroot /var/chroot/haproxy - - -1.4) Startup modes ------------------- -The service can start in several different modes : - - foreground / background - - quiet / normal / debug - -The default mode is normal, foreground, which means that the program doesn't -return once started. NEVER EVER use this mode in a system startup script, or -the system won't boot. It needs to be started in background, so that it -returns immediately after forking. That's accomplished by the 'daemon' option -in the 'global' section, which is the equivalent of the '-D' command line -argument. - -The '-db' command line argument overrides the 'daemon' and 'nbproc' global -options to make the process run in normal, foreground mode. - -Moreover, certain alert messages are still sent to the standard output even -in 'daemon' mode. To make them disappear, simply add the 'quiet' option in the -'global' section. This option has no command-line equivalent. - -Last, the 'debug' mode, enabled with the 'debug' option in the 'global' section, -and which is equivalent of the '-d' option, allows deep TCP/HTTP analysis, with -timestamped display of each connection, disconnection, and HTTP headers for both -ways. This mode is incompatible with 'daemon' and 'quiet' modes for obvious -reasons. - - -1.5) Increasing the overall processing power --------------------------------------------- -On multi-processor systems, it may seem to be a shame to use only one processor, -eventhough the load needed to saturate a recent processor is far above common -usage. Anyway, for very specific needs, the proxy can start several processes -between which the operating system will spread the incoming connections. The -number of processes is controlled by the 'nbproc' parameter in the 'global' -section. It defaults to 1, and obviously works only in 'daemon' mode. One -typical usage of this parameter has been to workaround the default per-process -file-descriptor limit that Solaris imposes to user processes. - -Example : ---------- - - global - daemon - quiet - nbproc 2 - - -1.6) Helping process management -------------------------------- -Haproxy now supports the notion of pidfile. If the '-p' command line argument, -or the 'pidfile' global option is followed with a file name, this file will be -removed, then filled with all children's pids, one per line (only in daemon -mode). This file is NOT within the chroot, which allows to work with a readonly - chroot. It will be owned by the user starting the process, and will have -permissions 0644. - -Example : ---------- - - global - daemon - quiet - nbproc 2 - pidfile /var/run/haproxy-private.pid - - # to stop only those processes among others : - # kill $( [ :[,...] ] - -- is the name of the instance. This name will be reported in - logs, so it is good to have it reflect the proxied service. No unicity test - is done on this name, and it's not mandatory for it to be unique, but highly - recommended. - -- is the IP address the proxy binds to. Empty address, '*' and - '0.0.0.0' all mean that the proxy listens to all valid addresses on the - system. - -- is either a unique port, or a port range for which the proxy will - accept connections for the IP address specified above. This range can 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 - couple consumes one socket (=a file descriptor), so it's easy to eat lots of - descriptors with a simple range. The couple must be used only once - among all instances running on a same system. Please note that attaching to - ports lower than 1024 need particular priviledges to start the program, which - are independent of the 'uid' parameter. - -- the : couple may be repeated indefinitely to require - the proxy to listen to other addresses and/or ports. To achieve this, simply - separate them with a coma. - -Examples : ---------- - listen http_proxy :80 - listen x11_proxy 127.0.0.1:6000-6009 - listen smtp_proxy 127.0.0.1:25,127.0.0.1:587 - listen ldap_proxy :389,:663 - -In the event that all addresses do not fit line width, it's preferable to -detach secondary addresses on other lines with the 'bind' keyword. If this -keyword is used, it's not even necessary to specify the first address on the -'listen' line, which sometimes makes multiple configuration handling easier : - - bind [ :[,...] ] - -Examples : ----------- - listen http_proxy - bind :80,:443 - bind 10.0.0.1:10080,10.0.0.1:10443 - - -2.1) Inhibiting a service -------------------------- -A service may be disabled for maintenance reasons, without needing to comment -out the whole section, simply by specifying the 'disabled' keyword in the -section to be disabled : - - listen smtp_proxy 0.0.0.0:25 - disabled - -Note: the 'enabled' keyword allows to enable a service which has been disabled - previously by a default configuration. - - -2.2) Modes of operation ------------------------ -A service can work in 3 different distinct modes : - - TCP - - HTTP - - health - -TCP mode --------- -In this mode, the service relays TCP connections as soon as they're established, -towards one or several servers. No processing is done on the stream. It's only -an association of source(addr:port) -> destination(addr:port). To use this mode, -you must specify 'mode tcp' in the 'listen' section. This is the default mode. - -Example : ---------- - listen smtp_proxy 0.0.0.0:25 - mode tcp - -HTTP mode ---------- -In this mode, the service relays TCP connections towards one or several servers, -when it has enough informations to decide, which normally means that all HTTP -headers have been read. Some of them may be scanned for a cookie or a pattern -matching a regex. To use this mode, specify 'mode http' in the 'listen' section. - -Example : ---------- - listen http_proxy 0.0.0.0:80 - mode http - -Health-checking mode --------------------- -This mode provides a way for external components to check the proxy's health. -It is meant to be used with intelligent load-balancers which can use send/expect -scripts to check for all of their servers' availability. This one simply accepts -the connection, returns the word 'OK' and closes it. If the 'option httpchk' is -set, then the reply will be 'HTTP/1.0 200 OK' with no data, so that it can be -tested from a tool which supports HTTP health-checks. To enable it, simply -specify 'health' as the working mode : - -Example : ---------- - # simple response : 'OK' - listen health_check 0.0.0.0:60000 - mode health - - # HTTP response : 'HTTP/1.0 200 OK' - listen http_health_check 0.0.0.0:60001 - mode health - option httpchk - -2.2.1 Monitoring ----------------- -Versions 1.1.32 and 1.2.6 provide a new solution to check the proxy's -availability without perturbating the service. The 'monitor-net' keyword was -created to specify a network of equipments which CANNOT use the service for -anything but health-checks. This is particularly suited to TCP proxies, because -it prevents the proxy from relaying the monitor's connection to the remote -server. - -When used with TCP, the connection is accepted then closed and nothing is -logged. This is enough for a front-end load-balancer to detect the service as -available. - -When used with HTTP, the connection is accepted, nothing is logged, the -following response is sent, then the session is closed : "HTTP/1.0 200 OK". -This is normally enough for any front-end HTTP load-balancer to detect the -service as available too, both with TCP and HTTP checks. - -Proxies using the "monitor-net" keyword can remove the "option dontlognull", as -it will make them log empty connections from hosts outside the monitoring -network. - -Example : ---------- - - listen tse-proxy - bind :3389,:1494,:5900 # TSE, ICA and VNC at once. - mode tcp - balance roundrobin - server tse-farm 192.168.1.10 - monitor-net 192.168.1.252/31 # L4 load-balancers on .252 and .253 - - -When the system executing the checks is located behind a proxy, the monitor-net -keyword cannot be used because haproxy will always see the proxy's address. To -overcome this limitation, version 1.2.15 brought the 'monitor-uri' keyword. It -defines an URI which will not be forwarded nor logged, but for which haproxy -will immediately send an "HTTP/1.0 200 OK" response. This makes it possible to -check the validity of the reverse-proxy->haproxy chain with one request. It can -be used in HTTPS checks in front of an stunnel -> haproxy combination for -instance. Obviously, this keyword is only valid in HTTP mode, otherwise there -is no notion of URI. Note that the method and HTTP versions are simply ignored. - -Example : ---------- - - listen stunnel_backend :8080 - mode http - balance roundrobin - server web1 192.168.1.10:80 check - server web2 192.168.1.11:80 check - monitor-uri /haproxy_test - - -2.3) Limiting the number of simultaneous connections ----------------------------------------------------- -The 'maxconn' parameter allows a proxy to refuse connections above a certain -amount of simultaneous ones. When the limit is reached, it simply stops -listening, but the system may still be accepting them because of the back log -queue. These connections will be processed later when other ones have freed -some slots. This provides a serialization effect which helps very fragile -servers resist to high loads. See further for system limitations. - -Example : ---------- - listen tiny_server 0.0.0.0:80 - maxconn 10 - - -2.4) Soft stop --------------- -It is possible to stop services without breaking existing connections by the -sending of the SIGUSR1 signal to the process. All services are then put into -soft-stop state, which means that they will refuse to accept new connections, -except for those which have a non-zero value in the 'grace' parameter, in which -case they will still accept connections for the specified amount of time, in -milliseconds. This makes it possible to tell a load-balancer that the service -is failing, while still doing the job during the time it needs to detect it. - -Note: active connections are never killed. In the worst case, the user will have -to wait for all of them to close or to time-out, or simply kill the process -normally (SIGTERM). The default 'grace' value is '0'. - -Example : ---------- - # enter soft stop after 'killall -USR1 haproxy' - # the service will still run 10 seconds after the signal - listen http_proxy 0.0.0.0:80 - mode http - grace 10000 - - # this port is dedicated to a load-balancer, and must fail immediately - listen health_check 0.0.0.0:60000 - mode health - grace 0 - - -As of version 1.2.8, a new soft-reconfiguration mechanism has been introduced. -It is now possible to "pause" all the proxies by sending a SIGTTOU signal to -the processes. This will disable the listening socket without breaking existing -connections. After that, sending a SIGTTIN signal to those processes enables -the listening sockets again. This is very useful to try to load a new -configuration or even a new version of haproxy without breaking existing -connections. If the load succeeds, then simply send a SIGUSR1 which will make -the previous proxies exit immediately once their sessions are closed ; and if -the load fails, then simply send a SIGTTIN to restore the service immediately. -Please note that the 'grace' parameter is ignored for SIGTTOU, as well as for -SIGUSR1 when the process was in the pause mode. Please also note that it would -be useful to save the pidfile before starting a new instance. - -This mechanism fully exploited since 1.2.11 with the '-st' and '-sf' options -(see below). - -2.4.1) Hot reconfiguration --------------------------- -The '-st' and '-sf' command line options are used to inform previously running -processes that a configuration is being reloaded. They will receive the SIGTTOU -signal to ask them to temporarily stop listening to the ports so that the new -process can grab them. If anything wrong happens, the new process will send -them a SIGTTIN to tell them to re-listen to the ports and continue their normal -work. Otherwise, it will either ask them to finish (-sf) their work then softly -exit, or immediately terminate (-st), breaking existing sessions. A typical use -of this allows a configuration reload without service interruption : - - # haproxy -p /var/run/haproxy.pid -sf $(cat /var/run/haproxy.pid) - - -2.5) Connections expiration time --------------------------------- -It is possible (and recommended) to configure several time-outs on TCP -connections. Three independent timers are adjustable with values specified -in milliseconds. A session will be terminated if either one of these timers -expire. - - - the time we accept to wait for data from the client, or for the client to - accept data : 'clitimeout' : - - # client time-out set to 2mn30. - clitimeout 150000 - - - the time we accept to wait for data from the server, or for the server to - accept data : 'srvtimeout' : - - # server time-out set to 30s. - srvtimeout 30000 - - - the time we accept to wait for a connection to establish on a server : - 'contimeout' : - - # we give up if the connection does not complete within 4 seconds - contimeout 4000 - -Notes : -------- - - 'contimeout' and 'srvtimeout' have no sense on 'health' mode servers ; - - under high loads, or with a saturated or defective network, it's possible - that some packets get lost. Since the first TCP retransmit only happens - after 3 seconds, a time-out equal to, or lower than 3 seconds cannot - compensate for a packet loss. A 4 seconds time-out seems a reasonable - minimum which will considerably reduce connection failures. - - starting with version 1.3.14, it is possible to specify timeouts in - arbitrary time units among { us, ms, s, m, h, d }. For this, the integer - value just has to be suffixed with the unit. - -2.6) Attempts to reconnect --------------------------- -After a connection failure to a server, it is possible to retry, potentially -on another server. This is useful if health-checks are too rare and you don't -want the clients to see the failures. The number of attempts to reconnect is -set by the 'retries' paramter. - -Example : ---------- - # we can retry 3 times max after a failure - retries 3 - -Please note that the reconnection attempt may lead to getting the connection -sent to a new server if the original one died between connection attempts. - - -2.7) Address of the dispatch server (deprecated) ------------------------------------------------- -The server which will be sent all new connections is defined by the 'dispatch' -parameter, in the form
:. It generally is dedicated to unknown -connections and will assign them a cookie, in case of HTTP persistence mode, -or simply is a single server in case of generic TCP proxy. This old mode is only -provided for backwards compatibility, but doesn't allow to check remote servers -state, and has a rather limited usage. All new setups should switch to 'balance' -mode. The principle of the dispatcher is to be able to perform the load -balancing itself, but work only on new clients so that the server doesn't need -to be a big machine. - -Example : ---------- - # all new connections go there - dispatch 192.168.1.2:80 - -Note : ------- -This parameter has no sense for 'health' servers, and is incompatible with -'balance' mode. - - -2.8) Outgoing source address ----------------------------- -It is often necessary to bind to a particular address when connecting to some -remote hosts. This is done via the 'source' parameter which is a per-proxy -parameter. A newer version may allow to fix different sources to reach different -servers. The syntax is 'source
[:]', where
is a valid -local address (or '0.0.0.0' or '*' or empty to let the system choose), and - is an optional parameter allowing the user to force the source port for -very specific needs. If the port is not specified or is '0', the system will -choose a free port. Note that as of version 1.1.18, the servers health checks -are also performed from the same source. - -Examples : ----------- - listen http_proxy *:80 - # all connections take 192.168.1.200 as source address - source 192.168.1.200:0 - - listen rlogin_proxy *:513 - # use address 192.168.1.200 and the reserved port 900 (needs to be root) - source 192.168.1.200:900 - - -2.9) Setting the cookie name ----------------------------- -In HTTP mode, it is possible to look for a particular cookie which will contain -a server identifier which should handle the connection. The cookie name is set -via the 'cookie' parameter. - -Example : ---------- - listen http_proxy :80 - mode http - cookie SERVERID - -It is possible to change the cookie behaviour to get a smarter persistence, -depending on applications. It is notably possible to delete or modify a cookie -emitted by a server, insert a cookie identifying the server in an HTTP response -and even add a header to tell upstream caches not to cache this response. - -Examples : ----------- - -To remove the cookie for direct accesses (ie when the server matches the one -which was specified in the client cookie) : - - cookie SERVERID indirect - -To replace the cookie value with the one assigned to the server if any (no -cookie will be created if the server does not provide one, nor if the -configuration does not provide one). This lets the application put the cookie -exactly on certain pages (eg: successful authentication) : - - cookie SERVERID rewrite - -To create a new cookie and assign the server identifier to it (in this case, all -servers should be associated with a valid cookie, since no cookie will simply -delete the cookie from the client's browser) : - - cookie SERVERID insert - -To reuse an existing application cookie and prefix it with the server's -identifier, and remove it in the request, use the 'prefix' option. This allows -to insert a haproxy in front of an application without risking to break clients -which does not support more than one cookie : - - cookie JSESSIONID prefix - -To insert a cookie and ensure that no upstream cache will store it, add the -'nocache' option : - - cookie SERVERID insert nocache - -To insert a cookie only after a POST request, add 'postonly' after 'insert'. -This has the advantage that there's no risk of caching, and that all pages -seen before the POST one can still be cached : - - cookie SERVERID insert postonly - -Notes : ------------ -- it is possible to combine 'insert' with 'indirect' or 'rewrite' to adapt to - applications which already generate the cookie with an invalid content. - -- in the case where 'insert' and 'indirect' are both specified, the cookie is - never transmitted to the server, since it wouldn't understand it. This is the - most application-transparent mode. - -- it is particularly recommended to use 'nocache' in 'insert' mode if any - upstream HTTP/1.0 cache is susceptible to cache the result, because this may - lead to many clients going to the same server, or even worse, some clients - having their server changed while retrieving a page from the cache. - -- the 'prefix' mode normally does not need 'indirect', 'nocache', nor - 'postonly', because just as in the 'rewrite' mode, it relies on the - application to know when a cookie can be emitted. However, since it has to - fix the cookie name in every subsequent requests, you must ensure that the - proxy will be used without any "HTTP keep-alive". Use option "httpclose" if - unsure. - -- when the application is well known and controlled, the best method is to - only add the persistence cookie on a POST form because it's up to the - application to select which page it wants the upstream servers to cache. In - this case, you would use 'insert postonly indirect'. - - -2.10) Associating a cookie value with a server ----------------------------------------------- -In HTTP mode, it's possible to associate a cookie value to each server. This -was initially used in combination with 'dispatch' mode to handle direct accesses -but it is now the standard way of doing the load balancing. The syntax is : - - server
: cookie - -- is any name which can be used to identify the server in the logs. --
: specifies where the server is bound. -- is the value to put in or to read from the cookie. - -Example : the 'SERVERID' cookie can be either 'server01' or 'server02' ---------- - listen http_proxy :80 - mode http - cookie SERVERID - dispatch 192.168.1.100:80 - server web1 192.168.1.1:80 cookie server01 - server web2 192.168.1.2:80 cookie server02 - -Warning : the syntax has changed since version 1.0 ! ---------- - - -2.11) Application Cookies -------------------------- -Since 1.2.4 it is possible to catch the cookie that comes from an -application server in order to apply "application session stickyness". -The server's response is searched for 'appsession' cookie, the first -'len' bytes are used for matching and it is stored for a period of -'timeout'. -The syntax is: - - appsession len timeout - -- is the cookie, the server uses for it's session-handling -- how many bytes/characters should be used for matching equal - sessions -- after this inactivaty time, in ms, the cookie will be deleted - from the sessionstore -- starting with version 1.3.14, it is possible to specify timeouts in - arbitrary time units among { us, ms, s, m, h, d }. For this, the integer - value just has to be prefixed with the unit. - -The appsession is only per 'listen' section possible. - -Example : ---------- - listen http_lb1 192.168.3.4:80 - mode http - capture request header Cookie len 200 - # Havind a ServerID cookie on the client allows him to reach - # the right server even after expiration of the appsession. - cookie ServerID insert nocache indirect - # Will memorize 52 bytes of the cookie 'JSESSIONID' and keep them - # for 3 hours. It will match it in the cookie and the URL field. - appsession JSESSIONID len 52 timeout 3h - server first1 10.3.9.2:10805 check inter 3000 cookie first - server secon1 10.3.9.3:10805 check inter 3000 cookie secon - server first1 10.3.9.4:10805 check inter 3000 cookie first - server secon2 10.3.9.5:10805 check inter 3000 cookie secon - option httpchk GET /test.jsp - - -3) Autonomous load balancer -=========================== - -The proxy can perform the load-balancing itself, both in TCP and in HTTP modes. -This is the most interesting mode which obsoletes the old 'dispatch' mode -described above. It has advantages such as server health monitoring, multiple -port binding and port mapping. To use this mode, the 'balance' keyword is used, -followed by the selected algorithm. Up to version 1.2.11, only 'roundrobin' was -available, which is also the default value if unspecified. Starting with -version 1.2.12, a new 'source' keyword appeared. A new 'uri' keyword was added -in version 1.3.10. In this mode, there will be no dispatch address, but the -proxy needs at least one server. - -Example : same as the last one, with internal load balancer ---------- - - listen http_proxy :80 - mode http - cookie SERVERID - balance roundrobin - server web1 192.168.1.1:80 cookie server01 - server web2 192.168.1.2:80 cookie server02 - - -Since version 1.1.22, it is possible to automatically determine on which port -the server will get the connection, depending on the port the client connected -to. Indeed, there now are 4 possible combinations for the server's field: - - - unspecified or '0' : - the connection will be sent to the same port as the one on which the proxy - received the client connection itself. - - - numerical value (the only one supported in versions earlier than 1.1.22) : - the connection will always be sent to the specified port. - - - '+' followed by a numerical value : - the connection will be sent to the same port as the one on which the proxy - received the connection, plus this value. - - - '-' followed by a numerical value : - the connection will be sent to the same port as the one on which the proxy - received the connection, minus this value. - -Examples : ----------- - -# same as previous example - - listen http_proxy :80 - mode http - cookie SERVERID - balance roundrobin - server web1 192.168.1.1 cookie server01 - server web2 192.168.1.2 cookie server02 - -# simultaneous relaying of ports 80, 81 and 8080-8089 - - listen http_proxy :80,:81,:8080-8089 - mode http - cookie SERVERID - balance roundrobin - server web1 192.168.1.1 cookie server01 - server web2 192.168.1.2 cookie server02 - -# relaying of TCP ports 25, 389 and 663 to ports 1025, 1389 and 1663 - - listen http_proxy :25,:389,:663 - mode tcp - balance roundrobin - server srv1 192.168.1.1:+1000 - server srv2 192.168.1.2:+1000 - -As previously stated, version 1.2.12 brought the 'source' keyword. When this -keyword is used, the client's IP address is hashed and evenly distributed among -the available servers so that a same source IP will always go to the same -server as long as there are no change in the number of available servers. This -can be used for instance to bind HTTP and HTTPS to the same server. It can also -be used to improve stickyness when one part of the client population does not -accept cookies. In this case, only those ones will be perturbated should a -server fail. - -NOTE: It is important to consider the fact that many clients surf the net - through proxy farms which assign different IP addresses for each - request. Others use dialup connections with a different IP at each - connection. Thus, the 'source' parameter should be used with extreme - care. - -Examples : ----------- - -# make a same IP go to the same server whatever the service - - listen http_proxy - bind :80,:443 - mode http - balance source - server web1 192.168.1.1 - server web2 192.168.1.2 - -# try to improve client-server binding by using both source IP and cookie : - - listen http_proxy :80 - mode http - cookie SERVERID - balance source - server web1 192.168.1.1 cookie server01 - server web2 192.168.1.2 cookie server02 - -As indicated above, the 'uri' keyword was introduced in version 1.3.10. It is -useful when load-balancing between reverse proxy-caches, because it will hash -the URI and use the hash result to select a server, thus optimizing the hit -rate on the caches, because the same URI will always reach the same cache. This -keyword is only allowed in HTTP mode. - -Example : ---------- - -# Always send a given URI to the same server - - listen http_proxy - bind :3128 - mode http - balance uri - server squid1 192.168.1.1 - server squid2 192.168.1.2 - -Version 1.3.14 introduced the "balance url_param" method. It consists in -relying on a parameter passed in the URL to perform a hash. This is mostly -useful for applications which do not have strict persistence requirements, -but for which it still provides a performance boost due to local caching. -Some of these applications may not be able to use a cookie for whatever reason, -but may be able to look for a parameter passed in the URL. If the parameter is -missing from the URL, then the 'round robin' method applies. - -A modifier may be added to specify that parameters in POST requests may be -found in the messsage body if the URL lacks a '?' separator character. -A wait limit may also be applied, if no limit is requested then -the default value is 48 octets, the minimum is 3. HAProxy may wait, until 48 -octets are received. If Content-Length is missing, or zero it need not -wait for more data then the client promissed to send. When Content-Length is -present, and more than ; then waiting is limited and it is assumed this -will be enough data to search for the presence of a parameter. If -Transfer-Encoding: chunked is used (unlikely), then the length of the first chunk -is the maximum number of bytes to wait for. - -balance url_param [check_post []] - -Caveats for using the check_post extension: - - - all POST requests are eligable 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) - -Limitations on inspecting the entity body of a POST: - - - 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. Scaning 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. - - -Example : ---------- - -# Hash the "basket_id" argument from the URL to determine the server - - listen http_proxy - bind :3128 - mode http - balance url_param basket_id - server ebiz1 192.168.1.1 - server ebiz2 192.168.1.2 - - -3.1) Server monitoring ----------------------- -It is possible to check the servers status by trying to establish TCP -connections or even sending HTTP requests to them. A server which fails to -reply to health checks as expected will not be used by the load balancing -algorithms. To enable monitoring, add the 'check' keyword on a server line. -It is possible to specify the interval between tests (in milliseconds) with -the 'inter' parameter, the number of failures supported before declaring that -the server has fallen down with the 'fall' parameter, and the number of valid -checks needed for the server to fully get up with the 'rise' parameter. Since -version 1.1.22, it is also possible to send checks to a different port -(mandatory when none is specified) with the 'port' parameter. The default -values are the following ones : - - - inter : 2000 - - rise : 2 - - fall : 3 - - port : default server port - - addr : specific address for the test (default = address server) - -The default mode consists in establishing TCP connections only. But in certain -types of application failures, it is often that the server continues to accept -connections because the system does it itself while the application is running -an endless loop, or is completely stuck. So in version 1.1.16 were introduced -HTTP health checks which only performed simple lightweight requests and analysed -the response. Now, as of version 1.1.23, it is possible to change the HTTP -method, the URI, and the HTTP version string (which even allows to send headers -with a dirty trick). To enable HTTP health-checks, use 'option httpchk'. - -By default, requests use the 'OPTIONS' method because it's very light and easy -to filter from logs, and does it on '/'. Only HTTP responses 2xx and 3xx are -considered valid ones, and only if they come before the time to send a new -request is reached ('inter' parameter). If some servers block this type of -request, 3 other forms help to forge a request : - - - option httpchk -> OPTIONS / HTTP/1.0 - - option httpchk URI -> OPTIONS HTTP/1.0 - - option httpchk METH URI -> HTTP/1.0 - - option httpchk METH URI VER -> - -Some people are using HAProxy to relay various TCP-based protocols such as -HTTPS, SMTP or LDAP, with the most common one being HTTPS. One problem commonly -encountered in data centers is the need to forward the traffic to far remote -servers while providing server fail-over. Often, TCP-only checks are not enough -because intermediate firewalls, load balancers or proxies might acknowledge the -connection before it reaches the real server. The only solution to this problem -is to send application-level health checks. Since the demand for HTTPS checks -is high, it has been implemented in 1.2.15 based on SSLv3 Client Hello packets. -To enable it, use 'option ssl-hello-chk'. It will send SSL CLIENT HELLO packets -to the servers, announcing support for most common cipher suites. If the server -responds what looks like a SERVER HELLO or an ALERT (refuses the ciphers) then -the response is considered as valid. Note that Apache does not generate a log -when it receives only an HELLO message, which makes this type of message -perfectly suit this need. - -Version 1.3.10 introduced the SMTP health check. By default, it sends -"HELO localhost" to the servers, and waits for the 250 message. Note that it -can also send a specific request : - - - option smtpchk -> sends "HELO localhost" - - option smtpchk EHLO mail.mydomain.com -> sends this ESMTP greeting - -See examples below. - -Since version 1.1.17, it is possible to specify backup servers. These servers -are only sollicited when no other server is available. This may only be useful -to serve a maintenance page, or define one active and one backup server (seldom -used in TCP mode). To make a server a backup one, simply add the 'backup' option -on its line. These servers also support cookies, so if a cookie is specified for -a backup server, clients assigned to this server will stick to it even when the -other ones come back. Conversely, if no cookie is assigned to such a server, -the clients will get their cookies removed (empty cookie = removal), and will -be balanced against other servers once they come back. Please note that there -is no load-balancing among backup servers by default. If there are several -backup servers, the second one will only be used when the first one dies, and -so on. To force load-balancing between backup servers, specify the 'allbackups' -option. - -Since version 1.1.22, it is possible to send health checks to a different port -than the service. It is mainly needed in setups where the server does not have -any predefined port, for instance when the port is deduced from the listening -port. For this, use the 'port' parameter followed by the port number which must -respond to health checks. It is also possible to send health checks to a -different address than the service. It makes it easier to use a dedicated check -daemon on the servers, for instance, check return contents and stop several -farms at once in the event of an error anywhere. - -Since version 1.1.17, it is also possible to visually check the status of all -servers at once. For this, you just have to send a SIGHUP signal to the proxy. -The servers status will be dumped into the logs at the 'notice' level, as well -as on if not closed. For this reason, it's always a good idea to have -one local log server at the 'notice' level. - -Since version 1.1.28 and 1.2.1, if an instance loses all its servers, an -emergency message will be sent in the logs to inform the administator that an -immediate action must be taken. - -Since version 1.1.30 and 1.2.3, several servers can share the same cookie -value. This is particularly useful in backup mode, to select alternate paths -for a given server for example, to provide soft-stop, or to direct the clients -to a temporary page during an application restart. The principle is that when -a server is dead, the proxy will first look for another server which shares the -same cookie value for every client which presents the cookie. If there is no -standard server for this cookie, it will then look for a backup server which -shares the same name. Please consult the architecture guide for more information. - -Examples : ----------- -# same setup as in paragraph 3) with TCP monitoring - listen http_proxy 0.0.0.0:80 - mode http - cookie SERVERID - balance roundrobin - server web1 192.168.1.1:80 cookie server01 check - server web2 192.168.1.2:80 cookie server02 check inter 500 rise 1 fall 2 - -# same with HTTP monitoring via 'OPTIONS / HTTP/1.0' - listen http_proxy 0.0.0.0:80 - mode http - cookie SERVERID - balance roundrobin - option httpchk - server web1 192.168.1.1:80 cookie server01 check - server web2 192.168.1.2:80 cookie server02 check inter 500 rise 1 fall 2 - -# same with HTTP monitoring via 'OPTIONS /index.html HTTP/1.0' - listen http_proxy 0.0.0.0:80 - mode http - cookie SERVERID - balance roundrobin - option httpchk /index.html - server web1 192.168.1.1:80 cookie server01 check - server web2 192.168.1.2:80 cookie server02 check inter 500 rise 1 fall 2 - -# same with HTTP monitoring via 'HEAD /index.jsp? HTTP/1.1\r\nHost: www' - listen http_proxy 0.0.0.0:80 - mode http - cookie SERVERID - balance roundrobin - option httpchk HEAD /index.jsp? HTTP/1.1\r\nHost:\ www - server web1 192.168.1.1:80 cookie server01 check - server web2 192.168.1.2:80 cookie server02 check inter 500 rise 1 fall 2 - -# Load-balancing with 'prefixed cookie' persistence, and soft-stop using an -# alternate port 81 on the server for health-checks. - listen http_proxy 0.0.0.0:80 - mode http - cookie JSESSIONID prefix - balance roundrobin - option httpchk HEAD /index.jsp? HTTP/1.1\r\nHost:\ www - server web1-norm 192.168.1.1:80 cookie s1 check port 81 - server web2-norm 192.168.1.2:80 cookie s2 check port 81 - server web1-stop 192.168.1.1:80 cookie s1 check port 80 backup - server web2-stop 192.168.1.2:80 cookie s2 check port 80 backup - -# automatic insertion of a cookie in the server's response, and automatic -# deletion of the cookie in the client request, while asking upstream caches -# not to cache replies. - listen web_appl 0.0.0.0:80 - mode http - cookie SERVERID insert nocache indirect - balance roundrobin - server web1 192.168.1.1:80 cookie server01 check - server web2 192.168.1.2:80 cookie server02 check - -# same with off-site application backup and local error pages server - listen web_appl 0.0.0.0:80 - mode http - cookie SERVERID insert nocache indirect - balance roundrobin - server web1 192.168.1.1:80 cookie server01 check - server web2 192.168.1.2:80 cookie server02 check - server web-backup 192.168.2.1:80 cookie server03 check backup - server web-excuse 192.168.3.1:80 check backup - -# SMTP+TLS relaying with health-checks and backup servers - - listen http_proxy :25,:587 - mode tcp - balance roundrobin - server srv1 192.168.1.1 check port 25 inter 30000 rise 1 fall 2 - server srv2 192.168.1.2 backup - -# HTTPS relaying with health-checks and backup servers - - listen http_proxy :443 - mode tcp - option ssl-hello-chk - balance roundrobin - server srv1 192.168.1.1 check inter 30000 rise 1 fall 2 - server srv2 192.168.1.2 backup - -# Load-balancing using a backup pool (requires haproxy 1.2.9) - listen http_proxy 0.0.0.0:80 - mode http - balance roundrobin - option httpchk - server inst1 192.168.1.1:80 cookie s1 check - server inst2 192.168.1.2:80 cookie s2 check - server inst3 192.168.1.3:80 cookie s3 check - server back1 192.168.1.10:80 check backup - server back2 192.168.1.11:80 check backup - option allbackups # all backups will be used - - -3.2) Redistribute connections in case of failure ------------------------------------------------- -In HTTP mode, if a server designated by a cookie does not respond, the 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 working servers. - -Example : ---------- - listen http_proxy 0.0.0.0:80 - mode http - cookie SERVERID - dispatch 192.168.1.100:80 - server web1 192.168.1.1:80 cookie server01 - server web2 192.168.1.2:80 cookie server02 - redispatch # send back to dispatch in case of connection failure - -Up to, and including version 1.1.16, this parameter only applied to connection -failures. Since version 1.1.17, it also applies to servers which have been -detected as failed by the health check mechanism. Indeed, a server may be broken -but still accepting connections, which would not solve every case. But it is -possible to conserve the old behaviour, that is, make a client insist on trying -to connect to a server even if it is said to be down, by setting the 'persist' -option : - - listen http_proxy 0.0.0.0:80 - mode http - option persist - cookie SERVERID - dispatch 192.168.1.100:80 - server web1 192.168.1.1:80 cookie server01 - server web2 192.168.1.2:80 cookie server02 - redispatch # send back to dispatch in case of connection failure - - -3.3) Assigning different weights to servers -------------------------------------------- -Sometimes you will need to bring new servers to increase your server farm's -capacity, but the new server will be either smaller (emergency use of anything -that fits) or bigger (when investing in new hardware). For this reason, it -might be wise to be able to send more clients to biggest servers. Till version -1.2.11, it was necessary to replicate the same server multiple times in the -configuration. Starting with 1.2.12, the 'weight' option is available. HAProxy -then computes the most homogenous possible map of servers based on their -weights so that the load gets distributed as smoothly as possible among them. -The weight, between 1 and 256, should reflect one server's capacity relative to -others. Weight 1 represents the lowest frequency and 256 the highest. This way, -if a server fails, the remaining capacities are still respected. - -Example : ---------- -# fair distribution among two opterons and one old pentium3 - - listen web_appl 0.0.0.0:80 - mode http - cookie SERVERID insert nocache indirect - balance roundrobin - server pentium3-800 192.168.1.1:80 cookie server01 weight 8 check - server opteron-2.0G 192.168.1.2:80 cookie server02 weight 20 check - server opteron-2.4G 192.168.1.3:80 cookie server03 weight 24 check - server web-backup1 192.168.2.1:80 cookie server04 check backup - server web-excuse 192.168.3.1:80 check backup - -Notes : -------- - - if unspecified, the default weight is 1 - - - the weight does not impact health checks, so it is cleaner to use weights - than replicating the same server several times - - - weights also work on backup servers if the 'allbackups' option is used - - - the weights also apply to the source address load balancing - ('balance source'). - - - whatever the weights, the first server will always be assigned first. This - is helpful for troubleshooting. - - - for the purists, the map calculation algorithm gives precedence to first - server, so the map is the most uniform when servers are declared in - ascending order relative to their weights. - -The load distribution will follow exactly this sequence : - - Request| 1 1 1 1 - number | 1 2 3 4 5 6 7 8 9 0 1 2 3 - --------+--------------------------- - p3-800 | X . . . . . . X . . . . . - opt-20 | . X . X . X . . . X . X . - opt-24 | . . X . X . X . X . X . X - - -3.4) Limiting the number of concurrent sessions on each server --------------------------------------------------------------- -Some pre-forked servers such as Apache suffer from too many concurrent -sessions, because it's very expensive to run hundreds or thousands of -processes on one system. One solution is to increase the number of servers -and load-balance between them, but it is a problem when the only goal is -to resist to short surges. - -To solve this problem, a new feature was implemented in HAProxy 1.2.13. -It's a per-server 'maxconn', associated with a per-server and a per-proxy -queue. This transforms haproxy into a request buffer between the thousands of -clients and the few servers. On many circumstances, lowering the maxconn value -will increase the server's performance and decrease the overall response times -because the servers will be less congested. - -When a request tries to reach any server, the first non-saturated server is -used, respective to the load balancing algorithm. If all servers are saturated, -then the request gets queued into the instance's global queue. It will be -dequeued once a server will have freed a session and all previously queued -requests have been processed. - -If a request references a particular server (eg: source hashing, or persistence -cookie), and if this server is full, then the request will be queued into the -server's dedicated queue. This queue has higher priority than the global queue, -so it's easier for already registered users to enter the site than for new -users. - -For this, the logs have been enhanced to show the number of sessions per -server, the request's position in the queue and the time spent in the queue. -This helps doing capacity planning. See the 'logs' section below for more info. - -Example : ---------- - # be nice with P3 which only has 256 MB of RAM. - listen web_appl 0.0.0.0:80 - maxconn 10000 - mode http - cookie SERVERID insert nocache indirect - balance roundrobin - server pentium3-800 192.168.1.1:80 cookie s1 weight 8 maxconn 100 check - server opteron-2.0G 192.168.1.2:80 cookie s2 weight 20 maxconn 300 check - server opteron-2.4G 192.168.1.3:80 cookie s3 weight 24 maxconn 300 check - server web-backup1 192.168.2.1:80 cookie s4 check maxconn 200 backup - server web-excuse 192.168.3.1:80 check backup - - -This was so much efficient at reducing the server's response time that some -users wanted to use low values to improve their server's performance. However, -they were not able anymore to handle very large loads because it was not -possible anymore to saturate the servers. For this reason, version 1.2.14 has -brought dynamic limitation with the addition of the parameter 'minconn'. When -this parameter is set along with maxconn, it will enable dynamic limitation -based on the instance's load. The maximum number of concurrent sessions on a -server will be proportionnal to the number of sessions on the instance relative -to its maxconn. A minimum of will be allowed whatever the load. This -will ensure that servers will perform at their best level under normal loads, -while still handling surges when needed. The dynamic limit is computed like -this : - - srv.dyn_limit = max(srv.minconn, srv.maxconn * inst.sess / inst.maxconn) - -Example : ---------- - # be nice with P3 which only has 256 MB of RAM. - listen web_appl 0.0.0.0:80 - maxconn 10000 - mode http - cookie SERVERID insert nocache indirect - balance roundrobin - server pentium3-800 192.168.1.1:80 cookie s1 weight 8 minconn 10 maxconn 100 check - server opteron-2.0G 192.168.1.2:80 cookie s2 weight 20 minconn 30 maxconn 300 check - server opteron-2.4G 192.168.1.3:80 cookie s3 weight 24 minconn 30 maxconn 300 check - server web-backup1 192.168.2.1:80 cookie s4 check maxconn 200 backup - server web-excuse 192.168.3.1:80 check backup - -In the example above, the server 'pentium3-800' will receive at most 100 -simultaneous sessions when the proxy instance will reach 10000 sessions, and -will receive only 10 simultaneous sessions when the proxy will be under 1000 -sessions. - -It is possible to limit server queue length in order to rebalance excess -sessions between less busy application servers IF session affinity isn't -hard functional requirement (for example it just gives huge performance boost -by keeping server-local caches hot and compact). 'maxqueue' option sets a -queue limit on a server, as in example below: - -... (just the same as in example above) - server pentium3-800 192.168.1.1:80 cookie s1 weight 8 minconn 10 maxconn 100 check maxqueue 50 - server opteron-2.0G 192.168.1.2:80 cookie s2 weight 20 minconn 30 maxconn 300 check maxqueue 200 - server opteron-2.4G 192.168.1.3:80 cookie s3 weight 24 minconn 30 maxconn 300 check - -Absence of 'maxqueue' option means unlimited queue. When queue gets filled -up to 'maxqueue' client session is moved from server-local queue to a global -one. - -Notes : -------- - - The requests will not stay indefinitely in the queue, they follow the - 'contimeout' parameter, and if a request cannot be dequeued within this - timeout because the server is saturated or because the queue is filled, - the session will expire with a 503 error. - - - if only is specified, it has the same effect as - - - setting too low values for maxconn might improve performance but might also - allow slow users to block access to the server for other users. - - -3.5) Dropping aborted requests ------------------------------- -In presence of very high loads, the servers will take some time to respond. The -per-proxy's 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. - -As there is no way to distinguish between a full STOP and a simple -shutdown(SHUT_WR) 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 (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 it is very -tempting to be able to abort the session early without polluting the servers. - -For this reason, a new option "abortonclose" was introduced in version 1.2.14. -By default (without the option) the behaviour is HTTP-compliant. But when the -option is specified, a session with an incoming channel closed will be aborted -if it's still possible, which means that it's either waiting for a connect() to -establish or it is queued waiting for a connection slot. 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. - -Example : ---------- - listen web_appl 0.0.0.0:80 - maxconn 10000 - mode http - cookie SERVERID insert nocache indirect - balance roundrobin - server web1 192.168.1.1:80 cookie s1 weight 10 maxconn 100 check - server web2 192.168.1.2:80 cookie s2 weight 10 maxconn 100 check - server web3 192.168.1.3:80 cookie s3 weight 10 maxconn 100 check - server bck1 192.168.2.1:80 cookie s4 check maxconn 200 backup - option abortonclose - - -4) Additionnal features -======================= - -Other features are available. They are transparent mode, event logging, header -rewriting/filtering, and the status as an HTML page. - - -4.1) Network features ---------------------- -4.1.1) Transparent mode ------------------------ -In HTTP mode, the 'transparent' keyword allows to intercept sessions which are -routed through the system hosting the proxy. This mode was implemented as a -replacement for the 'dispatch' mode, since connections without cookie will be -sent to the original address while known cookies will be sent to the servers. -This mode implies that the system can redirect sessions to a local port. - -Example : ---------- - listen http_proxy 0.0.0.0:65000 - mode http - transparent - cookie SERVERID - server server01 192.168.1.1:80 - server server02 192.168.1.2:80 - - # iptables -t nat -A PREROUTING -i eth0 -p tcp -d 192.168.1.100 \ - --dport 80 -j REDIRECT --to-ports 65000 - -Note : ------- -If the port is left unspecified on the server, the port the client connected to -will be used. This allows to relay a full port range without using transparent -mode nor thousands of file descriptors, provided that the system can redirect -sessions to local ports. - -Example : ---------- - # redirect all ports to local port 65000, then forward to the server on the - # original port. - listen http_proxy 0.0.0.0:65000 - mode tcp - server server01 192.168.1.1 check port 60000 - server server02 192.168.1.2 check port 60000 - - # iptables -t nat -A PREROUTING -i eth0 -p tcp -d 192.168.1.100 \ - -j REDIRECT --to-ports 65000 - -4.1.2) Per-server source address binding ----------------------------------------- -As of versions 1.1.30 and 1.2.3, it is possible to specify a particular source -to reach each server. This is useful when reaching backup servers from a -different LAN, or to use an alternate path to reach the same server. It is also -usable to provide source load-balancing for outgoing connections. Obviously, -the same source address is used to send health-checks. - -Example : ---------- - # use a particular source to reach both servers - listen http_proxy 0.0.0.0:65000 - mode http - balance roundrobin - server server01 192.168.1.1:80 source 192.168.2.13 - server server02 192.168.1.2:80 source 192.168.2.13 - -Example : ---------- - # use a particular source to reach each servers - listen http_proxy 0.0.0.0:65000 - mode http - balance roundrobin - server server01 192.168.1.1:80 source 192.168.1.1 - server server02 192.168.2.1:80 source 192.168.2.1 - -Example : ---------- - # provide source load-balancing to reach the same proxy through 2 WAN links - listen http_proxy 0.0.0.0:65000 - mode http - balance roundrobin - server remote-proxy-way1 192.168.1.1:3128 source 192.168.2.1 - server remote-proxy-way2 192.168.1.1:3128 source 192.168.3.1 - -Example : ---------- - # force a TCP connection to bind to a specific port - listen http_proxy 0.0.0.0:2000 - mode tcp - balance roundrobin - server srv1 192.168.1.1:80 source 192.168.2.1:20 - server srv2 192.168.1.2:80 source 192.168.2.1:20 - -4.1.3) TCP keep-alive ---------------------- -With version 1.2.7, it becomes possible to enable TCP keep-alives on both the -client and server sides. This makes it possible to prevent long sessions from -expiring on external layer 4 components such as firewalls and load-balancers. -It also allows the system to terminate dead sessions when no timeout has been -set (not recommanded). The proxy cannot set the keep-alive probes intervals nor -maximal count, consult your operating system manual for this. There are 3 -options to enable TCP keep-alive : - - option tcpka # enables keep-alive both on client and server side - option clitcpka # enables keep-alive only on client side - option srvtcpka # enables keep-alive only on server side - -4.1.4) TCP lingering --------------------- -It is possible to disable the system's lingering of data unacked by the client -at the end of a session. This is sometimes required when haproxy is used as a -front-end with lots of unreliable clients, and you observe thousands of sockets -in the FIN_WAIT state on the machine. This may be used in a frontend to affect -the client-side connection, as well as in a backend for the server-side -connection : - - option nolinger # disables data lingering - - -4.2) Event logging ------------------- - -HAProxy's strength certainly lies in its precise logs. It probably provides the -finest level of information available for such a product, which is very -important for troubleshooting complex environments. Standard log information -include client ports, TCP/HTTP state timers, precise session state at -termination and precise termination cause, information about decisions to -direct trafic to a server, and of course the ability to capture arbitrary -headers. - -In order to improve administrators reactivity, it offers a great transparency -about encountered problems, both internal and external, and it is possible to -send logs to different sources at the same time with different level filters : - - - global process-level logs (system errors, start/stop, etc..) - - per-listener system and internal errors (lack of resource, bugs, ...) - - per-listener external troubles (servers up/down, max connections) - - per-listener activity (client connections), either at the establishment or - at the termination. - -The ability to distribute different levels of logs to different log servers -allow several production teams to interact and to fix their problems as soon -as possible. For example, the system team might monitor system-wide errors, -while the application team might be monitoring the up/down for their servers in -real time, and the security team might analyze the activity logs with one hour -delay. - -4.2.1) Log levels ------------------ -TCP and HTTP connections can be logged with informations such as date, time, -source IP address, destination address, connection duration, response times, -HTTP request, the HTTP return code, number of bytes transmitted, the conditions -in which the session ended, and even exchanged cookies values, to track a -particular user's problems for example. All messages are sent to up to two -syslog servers. Consult section 1.1 for more info about log facilities. The -syntax follows : - - log [max_level_1] - log [max_level_2] -or - log global - -Note : ------- -The particular syntax 'log global' means that the same log configuration as the -'global' section will be used. - -Example : ---------- - listen http_proxy 0.0.0.0:80 - mode http - log 192.168.2.200 local3 - log 192.168.2.201 local4 - -4.2.2) Log format ------------------ -By default, connections are logged at the TCP level, as soon as the session -establishes between the client and the proxy. By enabling the 'tcplog' option, -the proxy will wait until the session ends to generate an enhanced log -containing more information such as session duration and its state during the -disconnection. The number of remaining session after disconnection is also -indicated (for the server, the listener, and the process). - -Example of TCP logging : ------------------------- - listen relais-tcp 0.0.0.0:8000 - mode tcp - option tcplog - log 192.168.2.200 local3 - ->>> haproxy[18989]: 127.0.0.1:34550 [15/Oct/2003:15:24:28] relais-tcp Srv1 0/0/5007 0 -- 1/1/1 0/0 - - Field Format Example - - 1 process_name '[' pid ']:' haproxy[18989]: - 2 client_ip ':' client_port 127.0.0.1:34550 - 3 '[' date ']' [15/Oct/2003:15:24:28] - 4 listener_name relais-tcp - 5 server_name Srv1 - 6 queue_time '/' connect_time '/' total_time 0/0/5007 - 7 bytes_read 0 - 8 termination_state -- - 9 srv_conn '/' listener_conn '/' process_conn 1/1/1 - 10 position in srv_queue / listener_queue 0/0 - - -Another option, 'httplog', provides more detailed information about HTTP -contents, such as the request and some cookies. In the event where an external -component would establish frequent connections to check the service, logs may be -full of useless lines. So it is possible not to log any session which didn't -transfer any data, by the setting of the 'dontlognull' option. This only has -effect on sessions which are established then closed. - -Example of HTTP logging : -------------------------- - listen http_proxy 0.0.0.0:80 - mode http - option httplog - option dontlognull - log 192.168.2.200 local3 - ->>> haproxy[674]: 127.0.0.1:33319 [15/Oct/2003:08:31:57] relais-http Srv1 9/0/7/147/723 200 243 - - ---- 34/34/15/8/3 0/0 "HEAD / HTTP/1.0" - -More complete example - haproxy[18989]: 10.0.0.1:34552 [15/Oct/2003:15:26:31] relais-http Srv1 3183/-1/-1/-1/11215 503 0 - - SC-- 205/202/150/137/+4 0/0 {w.ods.org|Mozilla} {} "HEAD / HTTP/1.0" - - Field Format Example - - 1 process_name '[' pid ']:' haproxy[18989]: - 2 client_ip ':' client_port 10.0.0.1:34552 - 3 '[' date ']' [15/Oct/2003:15:26:31] - 4 listener_name relais-http - 5 server_name Srv1 - 6 Tq '/' Tw '/' Tc '/' Tr '/' Tt 3183/-1/-1/-1/11215 - 7 HTTP_return_code 503 - 8 bytes_read 0 - 9 captured_request_cookie - - 10 captured_response_cookie - - 11 termination_state SC-- - 12 actconn '/' feconn '/' beconn '/' srv_conn '/' retries 205/202/150/137/+4 - 13 position in srv_queue / listener_queue 0/0 - 14 '{' captured_request_headers '}' {w.ods.org|Mozilla} - 15 '{' captured_response_headers '}' {} - 16 '"' HTTP_request '"' "HEAD / HTTP/1.0" - -Note for log parsers: the URI is ALWAYS the end of the line starting with the - first double quote '"'. - -The retries count may have additional '+' sign means that the connection had been -redispatched from one server to another shortly before retries limit (retries 4 -in above example) was depleted. - -The problem when logging at end of connection is that you have no clue about -what is happening during very long sessions. To workaround this problem, a -new option 'logasap' has been introduced in 1.1.28/1.2.1. When specified, the -proxy will log as soon as possible, just before data transfer begins. This means -that in case of TCP, it will still log the connection status to the server, and -in case of HTTP, it will log just after processing the server headers. In this -case, the number of bytes reported is the number of header bytes sent to the -client. - -In order to avoid confusion with normal logs, the total time field and the -number of bytes are prefixed with a '+' sign which means that real numbers are -certainly bigger. - -Example : ---------- - - listen http_proxy 0.0.0.0:80 - mode http - option httplog - option dontlognull - option logasap - log 192.168.2.200 local3 - ->>> haproxy[674]: 127.0.0.1:33320 [15/Oct/2003:08:32:17] relais-http Srv1 9/10/7/14/+30 200 +243 - - ---- 3/1/1/1/0 1/0 "GET /image.iso HTTP/1.0" - -4.2.3) Timing events --------------------- -Timers provide a great help in trouble shooting network problems. All values -are reported in milliseconds (ms). In HTTP mode, four control points are -reported under the form 'Tq/Tw/Tc/Tr/Tt' : - - - Tq: total time to get the client request. - It's the time elapsed between the moment the client connection was accepted - and the moment the proxy received the last HTTP header. The value '-1' - indicates that the end of headers (empty line) has never been seen. - - - Tw: total time spent in the queues waiting for a connection slot. It - accounts for listener's queue as well as the server's queue, and depends - on the queue size, and the time needed for the server to complete previous - sessions. The value '-1' means that the request was killed before reaching - the queue. - - - Tc: total time to establish the TCP connection to the server. - It's the time elapsed between the moment the proxy sent the connection - request, and the moment it was acknowledged, or between the TCP SYN packet - and the matching SYN/ACK in return. The value '-1' means that the - connection never established. - - - Tr: server response time. It's the time elapsed between the moment the - TCP connection was established to the server and the moment it send its - complete response header. It purely shows its request processing time, - without the network overhead due to the data transmission. The value '-1' - means that the last the response header (empty line) was never seen. - - - Tt: total session duration time, between the moment the proxy accepted it - and the moment both ends were closed. The exception is when the 'logasap' - option is specified. In this case, it only equals (Tq+Tw+Tc+Tr), and is - prefixed with a '+' sign. From this field, we can deduce Td, the data - transmission time, by substracting other timers when valid : - - Td = Tt - (Tq + Tw + Tc + Tr) - - Timers with '-1' values have to be excluded from this equation. - -In TCP mode ('option tcplog'), only Tw, Tc and Tt are reported. - -These timers provide precious indications on trouble causes. Since the TCP -protocol defines retransmit delays of 3, 6, 12... seconds, we know for sure -that timers close to multiples of 3s are nearly always related to packets lost -due to network problems (wires or negociation). Moreover, if is close to -a timeout value specified in the configuration, it often means that a session -has been aborted on time-out. - -Most common cases : - - - If Tq is close to 3000, a packet has probably been lost between the client - and the proxy. - - If Tc is close to 3000, a packet has probably been lost between the server - and the proxy during the server connection phase. This one should always be - very low (less than a few tens). - - If Tr is nearly always lower than 3000 except some rare values which seem to - be the average majored by 3000, there are probably some packets lost between - the proxy and the server. - - If Tt is often slightly higher than a time-out, it's often because the - client and the server use HTTP keep-alive and the session is maintained - after the response ends. Se further for how to disable HTTP keep-alive. - -Other cases ('xx' means any value to be ignored) : - -1/xx/xx/xx/Tt: the client was not able to send its complete request in time, - or that it aborted it too early. - Tq/-1/xx/xx/Tt: it was not possible to process the request, maybe because - servers were out of order. - Tq/Tw/-1/xx/Tt: the connection could not establish on the server. Either it - refused it or it timed out after Tt-(Tq+Tw) ms. - Tq/Tw/Tc/-1/Tt: the server has accepted the connection but did not return a - complete response in time, or it closed its connexion - unexpectedly, after Tt-(Tq+Tw+Tc) ms. - -4.2.4) Session state at disconnection -------------------------------------- -TCP and HTTP logs provide a session completion indicator in the - field, just before the number of active -connections. It is 2-characters long in TCP, and 4-characters long in -HTTP, each of which has a special meaning : - - - On the first character, a code reporting the first event which caused the - session to terminate : - - C : the TCP session was unexpectedly aborted by the client. - - S : the TCP session was unexpectedly aborted by the server, or the - server explicitly refused it. - - P : the session was prematurely aborted by the proxy, because of a - connection limit enforcement, because a DENY filter was matched, - or because of a security check which detected and blocked a - dangerous error in server response which might have caused - information leak (eg: cacheable cookie). - - R : a resource on the proxy has been exhausted (memory, sockets, source - ports, ...). Usually, this appears during the connection phase, and - system logs should contain a copy of the precise error. - - I : an internal error was identified by the proxy during a self-check. - This should NEVER happen, and you are encouraged to report any log - containing this, because this is a bug. - - c : the client-side time-out expired first. - - s : the server-side time-out expired first. - - - : normal session completion. - - - on the second character, the TCP/HTTP session state when it was closed : - - R : waiting for complete REQUEST from the client (HTTP only). Nothing - was sent to any server. - - Q : waiting in the QUEUE for a connection slot. This can only happen on - servers which have a 'maxconn' parameter set. No connection attempt - was made to any server. - - C : waiting for CONNECTION to establish on the server. The server might - at most have noticed a connection attempt. - - H : waiting for, receiving and processing server HEADERS (HTTP only). - - D : the session was in the DATA phase. - - L : the proxy was still transmitting LAST data to the client while the - server had already finished. - - T : the request was tarpitted. It has been held open on with the client - during the whole contimeout duration or untill the client closed. - - - : normal session completion after end of data transfer. - - - the third character tells whether the persistence cookie was provided by - the client (only in HTTP mode) : - - N : the client provided NO cookie. This is usually the case on new - connections. - - I : the client provided an INVALID cookie matching no known - server. This might be caused by a recent configuration change, - mixed cookies between HTTP/HTTPS sites, or an attack. - - D : the client provided a cookie designating a server which was DOWN, - so either the 'persist' option was used and the client was sent to - this server, or it was not set and the client was redispatched to - another server. - - V : the client provided a valid cookie, and was sent to the associated - server. - - - : does not apply (no cookie set in configuration). - - - the last character reports what operations were performed on the persistence - cookie returned by the server (only in HTTP mode) : - - N : NO cookie was provided by the server, and none was inserted either. - - I : no cookie was provided by the server, and the proxy INSERTED one. - - P : a cookie was PROVIDED by the server and transmitted as-is. - - R : the cookie provided by the server was REWRITTEN by the proxy. - - D : the cookie provided by the server was DELETED by the proxy. - - - : does not apply (no cookie set in configuration). - -The combination of the two first flags give a lot of information about what was -happening when the session terminated. It can be helpful to detect server -saturation, network troubles, local system resource starvation, attacks, etc... - -The most common termination flags combinations are indicated here. - - Flags Reason - CR The client aborted before sending a full request. Most probably the - request was done by hand using a telnet client, and aborted early. - - cR The client timed out before sending a full request. This is sometimes - caused by too large TCP MSS values on the client side for PPPoE - networks which cannot transport full-sized packets, or by clients - sending requests by hand and not typing fast enough. - - SC The server explicitly refused the connection (the proxy received a - TCP RST or an ICMP in return). Under some circumstances, it can - also be the network stack telling the proxy that the server is - unreachable (eg: no route, or no ARP response on local network). - - sC The connection to the server did not complete during contimeout. - - PC The proxy refused to establish a connection to the server because the - maxconn limit has been reached. The listener's maxconn parameter may - be increased in the proxy configuration, as well as the global - maxconn parameter. - - RC A local resource has been exhausted (memory, sockets, source ports) - preventing the connection to the server from establishing. The error - logs will tell precisely what was missing. Anyway, this can only be - solved by system tuning. - - cH The client timed out during a POST request. This is sometimes caused - by too large TCP MSS values for PPPoE networks which cannot transport - full-sized packets. - - CH The client aborted while waiting for the server to start responding. - It might be the server taking too long to respond or the client - clicking the 'Stop' button too fast. - - CQ The client aborted while its session was queued, waiting for a server - with enough empty slots to accept it. It might be that either all the - servers were saturated or the assigned server taking too long to - respond. - - CT The client aborted while its session was tarpitted. - - sQ The session spent too much time in queue and has been expired. - - SH The server aborted before sending its full headers, or it crashed. - - sH The server failed to reply during the srvtimeout delay, which - indicates too long transactions, probably caused by back-end - saturation. The only solutions are to fix the problem on the - application or to increase the 'srvtimeout' parameter to support - longer delays (at the risk of the client giving up anyway). - - PR The proxy blocked the client's request, either because of an invalid - HTTP syntax, in which case it returned an HTTP 400 error to the - client, or because a deny filter matched, in which case it returned - an HTTP 403 error. - - PH The proxy blocked the server's response, because it was invalid, - incomplete, dangerous (cache control), or matched a security filter. - In any case, an HTTP 502 error is sent to the client. - - PT The proxy blocked the client's request and has tarpitted its - connection before returning it a 500 server error. Nothing was sent - to the server. - - cD The client did not read any data for as long as the clitimeout delay. - This is often caused by network failures on the client side. - - CD The client unexpectedly aborted during data transfer. This is either - caused by a browser crash, or by a keep-alive session between the - server and the client terminated first by the client. - - sD The server did nothing during the srvtimeout delay. This is often - caused by too short timeouts on L4 equipements before the server - (firewalls, load-balancers, ...). - -4.2.5) Non-printable characters -------------------------------- -As of version 1.1.29, non-printable characters are not sent as-is into log -files, but are converted to their two-digits hexadecimal representation, -prefixed by the character '#'. The only characters that can now be logged -without being escaped are between 32 and 126 (inclusive). Obviously, the -escape character '#' is also encoded to avoid any ambiguity. It is the same for -the character '"', as well as '{', '|' and '}' when logging headers. - -4.2.6) Capturing HTTP headers and cookies ------------------------------------------ -Version 1.1.23 brought cookie capture, and 1.1.29 the header capture. All this -is performed using the 'capture' keyword. - -Cookie capture makes it easy to track a complete user session. The syntax is : - - capture cookie len - -This will enable cookie capture from both requests and responses. This way, -it's easy to detect when a user switches to a new session for example, because -the server will reassign it a new cookie. - -The FIRST cookie whose name starts with will be captured, and -logged as 'NAME=value', without exceeding characters (64 max). -When the cookie name is fixed and known, it's preferable to suffix '=' to it to -ensure that no other cookie will be logged. - -Examples : ----------- - # capture the first cookie whose name starts with "ASPSESSION" - capture cookie ASPSESSION len 32 - - # capture the first cookie whose name is exactly "vgnvisitor" - capture cookie vgnvisitor= len 32 - -In the logs, the field preceeding the completion indicator contains the cookie -value as sent by the server, preceeded by the cookie value as sent by the -client. Each of these field is replaced with '-' when no cookie was seen or -when the option is disabled. - -Header captures have a different goal. They are useful to track unique request -identifiers set by a previous proxy, virtual host names, user-agents, POST -content-length, referrers, etc. In the response, one can search for information -about the response length, how the server asked the cache to behave, or an -object location during a redirection. As for cookie captures, it is both -possible to include request headers and response headers at the same time. The -syntax is : - - capture request header len - capture response header len - -Note: Header names are not case-sensitive. - -Examples: ---------- - # keep the name of the virtual server - capture request header Host len 20 - # keep the amount of data uploaded during a POST - capture request header Content-Length len 10 - - # note the expected cache behaviour on the response - capture response header Cache-Control len 8 - # note the URL location during a redirection - capture response header Location len 20 - -Non-existant headers are logged as empty strings, and if one header appears more -than once, only its last occurence will be kept. Request headers are grouped -within braces '{' and '}' in the same order as they were declared, and delimited -with a vertical bar '|' without any space. Response headers follow the same -representation, but are displayed after a space following the request headers -block. These blocks are displayed just before the HTTP request in the logs. - -Example : - - Config: - - capture request header Host len 20 - capture request header Content-Length len 10 - capture request header Referer len 20 - capture response header Server len 20 - capture response header Content-Length len 10 - capture response header Cache-Control len 8 - capture response header Via len 20 - capture response header Location len 20 - - Log : - - Aug 9 20:26:09 localhost haproxy[2022]: 127.0.0.1:34014 [09/Aug/2004:20:26:09] relais-http netcache 0/0/0/162/+162 200 +350 - - ---- 0/0/0 0/0 {fr.adserver.yahoo.co||http://fr.f416.mail.} {|864|private||} "GET http://fr.adserver.yahoo.com/" - Aug 9 20:30:46 localhost haproxy[2022]: 127.0.0.1:34020 [09/Aug/2004:20:30:46] relais-http netcache 0/0/0/182/+182 200 +279 - - ---- 0/0/0 0/0 {w.ods.org||} {Formilux/0.1.8|3495|||} "GET http://w.ods.org/sytadin.html HTTP/1.1" - Aug 9 20:30:46 localhost haproxy[2022]: 127.0.0.1:34028 [09/Aug/2004:20:30:46] relais-http netcache 0/0/2/126/+128 200 +223 - - ---- 0/0/0 0/0 {www.infotrafic.com||http://w.ods.org/syt} {Apache/2.0.40 (Red H|9068|||} "GET http://www.infotrafic.com/images/live/cartesidf/grandes/idf_ne.png HTTP/1.1" - - -4.2.7) Examples of logs ------------------------ -- haproxy[674]: 127.0.0.1:33319 [15/Oct/2003:08:31:57] relais-http Srv1 6559/0/7/147/6723 200 243 - - ---- 1/3/5 0/0 "HEAD / HTTP/1.0" - => long request (6.5s) entered by hand through 'telnet'. The server replied - in 147 ms, and the session ended normally ('----') - -- haproxy[674]: 127.0.0.1:33319 [15/Oct/2003:08:31:57] relais-http Srv1 6559/1230/7/147/6870 200 243 - - ---- 99/239/324 0/9 "HEAD / HTTP/1.0" - => Idem, but the request was queued in the global queue behind 9 other - requests, and waited there for 1230 ms. - -- haproxy[674]: 127.0.0.1:33320 [15/Oct/2003:08:32:17] relais-http Srv1 9/0/7/14/+30 200 +243 - - ---- 1/3/3 0/0 "GET /image.iso HTTP/1.0" - => request for a long data transfer. The 'logasap' option was specified, so - the log was produced just before transfering data. The server replied in - 14 ms, 243 bytes of headers were sent to the client, and total time from - accept to first data byte is 30 ms. - -- haproxy[674]: 127.0.0.1:33320 [15/Oct/2003:08:32:17] relais-http Srv1 9/0/7/14/30 502 243 - - PH-- 0/2/3 0/0 "GET /cgi-bin/bug.cgi? HTTP/1.0" - => the proxy blocked a server response either because of an 'rspdeny' or - 'rspideny' filter, or because it blocked sensible information which risked - being cached. In this case, the response is replaced with a '502 bad - gateway'. - -- haproxy[18113]: 127.0.0.1:34548 [15/Oct/2003:15:18:55] relais-http -1/-1/-1/-1/8490 -1 0 - - CR-- 0/2/2 0/0 "" - => the client never completed its request and aborted itself ('C---') after - 8.5s, while the proxy was waiting for the request headers ('-R--'). - Nothing was sent to the server. - -- haproxy[18113]: 127.0.0.1:34549 [15/Oct/2003:15:19:06] relais-http -1/-1/-1/-1/50001 408 0 - - cR-- 2/2 0/0 "" - => The client never completed its request, which was aborted by the time-out - ('c---') after 50s, while the proxy was waiting for the request headers ('-R--'). - Nothing was sent to the server, but the proxy could send a 408 return code - to the client. - -- haproxy[18989]: 127.0.0.1:34550 [15/Oct/2003:15:24:28] relais-tcp Srv1 0/0/5007 0 cD 0/0/0 0/0 - => This is a 'tcplog' entry. Client-side time-out ('c----') occured after 5s. - -- haproxy[18989]: 10.0.0.1:34552 [15/Oct/2003:15:26:31] relais-http Srv1 3183/-1/-1/-1/11215 503 0 - - SC-- 115/202/205 0/0 "HEAD / HTTP/1.0" - => The request took 3s to complete (probably a network problem), and the - connection to the server failed ('SC--') after 4 attemps of 2 seconds - (config says 'retries 3'), then a 503 error code was sent to the client. - There were 115 connections on this server, 202 connections on this proxy, - and 205 on the global process. It is possible that the server refused the - connection because of too many already established. - - -4.3) HTTP header manipulation ------------------------------ -In HTTP mode, it is possible to rewrite, add or delete some of the request and -response headers based on regular expressions. It is also possible to block a -request or a response if a particular header matches a regular expression, -which is enough to stops most elementary protocol attacks, and to protect -against information leak from the internal network. But there is a limitation -to this : since haproxy's HTTP engine knows nothing about keep-alive, only -headers passed during the first request of a TCP session will be seen. All -subsequent headers will be considered data only and not analyzed. Furthermore, -haproxy doesn't touch data contents, it stops at the end of headers. - -The syntax is : - reqadd to add a header to the request - reqrep to modify the request - reqirep same, but ignoring the case - reqdel to delete a header in the request - reqidel same, but ignoring the case - reqallow definitely allow a request if a header matches - reqiallow same, but ignoring the case - reqdeny denies a request if a header matches - reqideny same, but ignoring the case - reqpass ignore a header matching - reqipass same, but ignoring the case - reqtarpit tarpit a request matching - reqitarpit same, but ignoring the case - - rspadd to add a header to the response - rsprep to modify the response - rspirep same, but ignoring the case - rspdel to delete the response - rspidel same, but ignoring the case - rspdeny replaces a response with a HTTP 502 if a header matches - rspideny same, but ignoring the case - - - is a POSIX regular expression (regex) which supports grouping through -parenthesis (without the backslash). Spaces and other delimiters must be -prefixed with a backslash ('\') to avoid confusion with a field delimiter. -Other characters may be prefixed with a backslash to change their meaning : - - \t for a tab - \r for a carriage return (CR) - \n for a new line (LF) - \ to mark a space and differentiate it from a delimiter - \# to mark a sharp and differentiate it from a comment - \\ to use a backslash in a regex - \\\\ to use a backslash in the text (*2 for regex, *2 for haproxy) - \xXX to write the ASCII hex code XX as in the C language - - - contains the string to be used to replace the largest portion of text -matching the regex. It can make use of the special characters above, and can -reference a substring delimited by parenthesis in the regex, by the group -numerical order from 0 to 9 (0 being the entire line). In this case, you would -write a backslash ('\') immediately followed by one digit indicating the group -position. - - represents the string which will systematically be added after the last -header line. It can also use special characters above. - -Notes : -------- - - the first line is considered as a header, which makes it possible to rewrite - or filter HTTP requests URIs or response codes. - - 'reqrep' is the equivalent of 'cliexp' in version 1.0, and 'rsprep' is the - equivalent of 'srvexp' in 1.0. Those names are still supported but - deprecated. - - for performances reasons, the number of characters added to a request or to - a response is limited to 4096 since version 1.1.5 (it was 256 before). This - value is easy to modify in the code if needed (#define). If it is too short - on occasional uses, it is possible to gain some space by removing some - useless headers before adding new ones. - - a denied request will generate an "HTTP 403 forbidden" response, while a - denied response will generate an "HTTP 502 Bad gateway" response. - - a tarpitted request will be held open on the client side for a duration - defined in the contimeout parameter, or untill the client aborts. Nothing - will be sent to any server. When the timeout is reached, the proxy will - reply with a 500 server error response so that the attacker does not - suspect it has been tarpitted. The logs may report the 500, but the - termination flags will indicate 'PT' in this case. - - -Examples : ----------- - ###### a few examples ###### - - # rewrite 'online.fr' instead of 'free.fr' for GET and POST requests - reqrep ^(GET\ .*)(.free.fr)(.*) \1.online.fr\3 - reqrep ^(POST\ .*)(.free.fr)(.*) \1.online.fr\3 - - # force proxy connections to close - reqirep ^Proxy-Connection:.* Proxy-Connection:\ close - # rewrite locations - rspirep ^(Location:\ )([^:]*://[^/]*)(.*) \1\3 - - ###### A full configuration being used on production ###### - - # Every header should end with a colon followed by one space. - reqideny ^[^:\ ]*[\ ]*$ - - # block Apache chunk exploit - reqideny ^Transfer-Encoding:[\ ]*chunked - reqideny ^Host:\ apache- - - # block annoying worms that fill the logs... - reqideny ^[^:\ ]*\ .*(\.|%2e)(\.|%2e)(%2f|%5c|/|\\\\) - reqideny ^[^:\ ]*\ ([^\ ]*\ [^\ ]*\ |.*%00) - reqideny ^[^:\ ]*\ .*