| ------------------- |
| HAProxy |
| Reference Manual |
| ------------------- |
| version 1.3.2 |
| willy tarreau |
| 2006/09/03 |
| |
| ============ |
| | 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 <configuration file> |
| -n <high limit for the total number of simultaneous connections> |
| = 'maxconn' in 'global' section |
| -N <high limit for the per-listener number of simultaneous connections> |
| = 'maxconn' in 'listen' or 'default' sections |
| -d starts in foregreound with debugging mode enabled |
| -D starts in 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 <pidfile> 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() |
| -ds disables use of speculative epoll() |
| -de disables use of epoll() |
| -dp disables use of poll() |
| -db disables background mode (stays in foreground, useful for debugging) |
| -m <megs> enforces a memory usage limit to a maximum of <megs> 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 <address> <facility> [max_level] |
| - maxconn <number> |
| - uid <user id> |
| - gid <group id> |
| - user <user name> |
| - group <group name> |
| - chroot <directory> |
| - nbproc <number> |
| - daemon |
| - debug |
| - nokqueue |
| - nosepoll |
| - noepoll |
| - nopoll |
| - quiet |
| - pidfile <file> |
| - ulimit-n <number> |
| - stats |
| - tune.maxpollevents <number> |
| |
| |
| 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 <ip_address> <facility> [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 <max_level> 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 $(</var/run/haproxy-private.pid) |
| |
| # to reload a new configuration with minimal service impact and without |
| # breaking existing sessions : |
| # haproxy -f haproxy.cfg -p /var/run/haproxy-private.pid -sf $(</var/run/haproxy-private.pid) |
| |
| 1.7) Polling mechanisms |
| ----------------------- |
| Starting from version 1.2.5, haproxy supports the poll() and epoll() polling |
| mechanisms. On systems where select() is limited by FD_SETSIZE (like Solaris), |
| poll() can be an interesting alternative. Performance tests show that Solaris' |
| poll() performance does not decay as fast as the numbers of sockets increase, |
| making it a safe solution for high loads. However, Solaris already uses poll() |
| to emulate select(), so as long as the number of sockets has no reason to go |
| higher than FD_SETSIZE, poll() should not provide any better performance. On |
| Linux systems with the epoll() patch (or any 2.6 version), haproxy will use |
| epoll() which is extremely fast and non dependant on the number of sockets. |
| Tests have shown constant performance from 1 to 20000 simultaneous sessions. |
| Version 1.3.9 introduced kqueue() for FreeBSD/OpenBSD, and speculative epoll() |
| which consists in trying to perform I/O before queuing the events via syscalls. |
| |
| In order to optimize latency, it is now possible to limit the number of events |
| returned by a single call to poll. The limit is fixed to 200 by default. If a |
| smaller latency is seeked, it may be useful to reduce this value by using the |
| 'tune.maxpollevents' parameter in the 'global' section. Increasing it will |
| slightly save CPU cycles in presence of large number of connections. |
| |
| Haproxy will use kqueue() or speculative epoll() when available, then epoll(), |
| and will fall back to poll(), then to select(). However, if for any reason you |
| need to disable epoll() or poll() (eg. because of a bug or just to compare |
| performance), new global options have been created for this matter : 'nosepoll', |
| 'nokqueue', 'noepoll' and 'nopoll'. |
| |
| Example : |
| --------- |
| |
| global |
| # use only select() |
| noepoll |
| nopoll |
| tune.maxpollevents 100 |
| |
| Note : |
| ------ |
| For the sake of configuration file portability, these options are accepted but |
| ignored if the poll() or epoll() mechanisms have not been enabled at compile |
| time. |
| |
| To make debugging easier, the '-de' runtime argument disables epoll support, |
| the '-dp' argument disables poll support, '-dk' disables kqueue and '-ds' |
| disables speculative epoll(). They are respectively equivalent to 'noepoll', |
| 'nopoll', 'nokqueue' and 'nosepoll'. |
| |
| |
| 2) Declaration of a listening service |
| ===================================== |
| |
| Service sections start with the 'listen' keyword : |
| |
| listen <instance_name> [ <IP_address>:<port_range>[,...] ] |
| |
| - <instance_name> 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. |
| |
| - <IP_address> 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. |
| |
| - <port_range> 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 <addr:port> |
| couple consumes one socket (=a file descriptor), so it's easy to eat lots of |
| descriptors with a simple range. The <addr:port> 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 independant of the 'uid' parameter. |
| |
| - the <IP_address>:<port_range> 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 [ <IP_address>:<port_range>[,...] ] |
| |
| 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 independant 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. |
| |
| |
| 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 <address>:<port>. 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 <address>[:<port>]', where <address> is a valid |
| local address (or '0.0.0.0' or '*' or empty to let the system choose), and |
| <port> 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 <identifier> <address>:<port> cookie <value> |
| |
| - <identifier> is any name which can be used to identify the server in the logs. |
| - <address>:<port> specifies where the server is bound. |
| - <value> 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 <session_cookie> len <match_length> timeout <holdtime> |
| |
| - <session_cookie> is the cookie, the server uses for it's session-handling |
| - <match_length> how many bytes/characters should be used for matching equal |
| sessions |
| - <holdtime> after this inactivaty time, in ms, the cookie will be deleted |
| from the sessionstore |
| |
| 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 10800000 |
| 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 <port> 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. |
| |
| 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 <URI> HTTP/1.0 |
| - option httpchk METH URI -> <METH> <URI> HTTP/1.0 |
| - option httpchk METH URI VER -> <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 <stderr> 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 <minconn> 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 <minconn> is specified, it has the same effect as <maxconn> |
| |
| - 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 <address_1> <facility_1> [max_level_1] |
| log <address_2> <facility_2> [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 - - ---- 2/3/3 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-- 137/202/205 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 srv_conn '/' listener_conn '/' process_conn 137/202/205 |
| 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 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 mean 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 - - ---- 1/1/3 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 <Tt> 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 |
| <termination_state> 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 <cookie_prefix> len <capture_length> |
| |
| 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 <cookie_prefix> will be captured, and |
| logged as 'NAME=value', without exceeding <capture_length> 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 <name> len <max length> |
| capture response header <name> len <max length> |
| |
| 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 <NOSRV> -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 <NOSRV> -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 <string> to add a header to the request |
| reqrep <search> <replace> to modify the request |
| reqirep <search> <replace> same, but ignoring the case |
| reqdel <search> to delete a header in the request |
| reqidel <search> same, but ignoring the case |
| reqallow <search> definitely allow a request if a header matches <search> |
| reqiallow <search> same, but ignoring the case |
| reqdeny <search> denies a request if a header matches <search> |
| reqideny <search> same, but ignoring the case |
| reqpass <search> ignore a header matching <search> |
| reqipass <search> same, but ignoring the case |
| reqtarpit <search> tarpit a request matching <search> |
| reqitarpit <search> same, but ignoring the case |
| |
| rspadd <string> to add a header to the response |
| rsprep <search> <replace> to modify the response |
| rspirep <search> <replace> same, but ignoring the case |
| rspdel <search> to delete the response |
| rspidel <search> same, but ignoring the case |
| rspdeny <search> replaces a response with a HTTP 502 if a header matches <search> |
| rspideny <search> same, but ignoring the case |
| |
| |
| <search> 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 |
| |
| |
| <replace> 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. |
| |
| <string> 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 ^[^:\ ]*\ .*<script |
| reqideny ^[^:\ ]*\ .*/(root\.exe\?|cmd\.exe\?|default\.ida\?) |
| |
| # tarpit attacks on the login page. |
| reqtarpit ^[^:\ ]*\ .*\.php?login=[^0-9] |
| |
| # allow other syntactically valid requests, and block any other method |
| reqipass ^(GET|POST|HEAD|OPTIONS)\ /.*\ HTTP/1\.[01]$ |
| reqipass ^OPTIONS\ \\*\ HTTP/1\.[01]$ |
| reqideny ^[^:\ ]*\ |
| |
| # force connection:close, thus disabling HTTP keep-alive |
| option httpclose |
| |
| # change the server name |
| rspidel ^Server:\ |
| rspadd Server:\ Formilux/0.1.8 |
| |
| |
| Also, the 'forwardfor' option creates an HTTP 'X-Forwarded-For' header which |
| contains the client's IP address. This is useful to let the final web server |
| know what the client address was (eg for statistics on domains). Starting with |
| version 1.3.8, it is possible to specify the "except" keyword followed by a |
| source IP address or network for which no header will be added. This is very |
| useful when another reverse-proxy which already adds the header runs on the |
| same machine or in a known DMZ, the most common case being the local use of |
| stunnel on the same system. |
| |
| Last, the 'httpclose' option removes any 'Connection' header both ways, and |
| adds a 'Connection: close' header in each direction. This makes it easier to |
| disable HTTP keep-alive than the previous 4-rules block. |
| |
| Example : |
| --------- |
| listen http_proxy 0.0.0.0:80 |
| mode http |
| log global |
| option httplog |
| option dontlognull |
| option forwardfor except 127.0.0.1/8 |
| option httpclose |
| |
| Note that some HTTP servers do not necessarily close the connections when they |
| receive the 'Connection: close', and if the client does not close either, then |
| the connection will be maintained up to the time-out. This translates into high |
| number of simultaneous sessions and high global session times in the logs. To |
| workaround this, a new option 'forceclose' appeared in version 1.2.9 to enforce |
| the closing of the outgoing server channel as soon as the server begins to |
| reply and only if the request buffer is empty. Note that this should NOT be |
| used if CONNECT requests are expected between the client and the server. The |
| 'forceclose' option implies the 'httpclose' option. |
| |
| Example : |
| --------- |
| listen http_proxy 0.0.0.0:80 |
| mode http |
| log global |
| option httplog |
| option dontlognull |
| option forwardfor |
| option forceclose |
| |
| |
| 4.4) Load balancing with persistence |
| ------------------------------------ |
| Combining cookie insertion with internal load balancing allows to transparently |
| bring persistence to applications. The principle is quite simple : |
| - assign a cookie value to each server |
| - enable the load balancing between servers |
| - insert a cookie into responses resulting from the balancing algorithm |
| (indirect accesses), end ensure that no upstream proxy will cache it. |
| - remove the cookie in the request headers so that the application never sees |
| it. |
| |
| Example : |
| --------- |
| listen application 0.0.0.0:80 |
| mode http |
| cookie SERVERID insert nocache indirect |
| balance roundrobin |
| server srv1 192.168.1.1:80 cookie server01 check |
| server srv2 192.168.1.2:80 cookie server02 check |
| |
| The other solution brought by versions 1.1.30 and 1.2.3 is to reuse a cookie |
| from the server, and prefix the server's name to it. In this case, don't forget |
| to force "httpclose" mode so that you can be assured that every subsequent |
| request will have its cookie fixed. |
| |
| listen application 0.0.0.0:80 |
| mode http |
| cookie JSESSIONID prefix |
| balance roundrobin |
| server srv1 192.168.1.1:80 cookie srv1 check |
| server srv2 192.168.1.2:80 cookie srv2 check |
| option httpclose |
| |
| |
| 4.5) Protection against information leak from the servers |
| --------------------------------------------------------- |
| In versions 1.1.28/1.2.1, a new option 'checkcache' was created. It carefully |
| checks 'Cache-control', 'Pragma' and 'Set-cookie' headers in server response |
| to check if there's a risk of caching a cookie on a client-side proxy. When this |
| option is enabled, the only responses which can be delivered to the client are : |
| - all those without 'Set-Cookie' header ; |
| - all those with a return code other than 200, 203, 206, 300, 301, 410, |
| provided that the server has not set a 'Cache-control: public' header ; |
| - all those that come from a POST request, provided that the server has not |
| set a 'Cache-Control: public' header ; |
| - those with a 'Pragma: no-cache' header |
| - those with a 'Cache-control: private' header |
| - those with a 'Cache-control: no-store' header |
| - those with a 'Cache-control: max-age=0' header |
| - those with a 'Cache-control: s-maxage=0' header |
| - those with a 'Cache-control: no-cache' header |
| - those with a 'Cache-control: no-cache="set-cookie"' header |
| - those with a 'Cache-control: no-cache="set-cookie,' header |
| (allowing other fields after set-cookie) |
| |
| If a response doesn't respect these requirements, then it will be blocked just |
| as if it was from an 'rspdeny' filter, with an "HTTP 502 bad gateway". The |
| session state shows "PH--" meaning that the proxy blocked the response during |
| headers processing. Additionnaly, an alert will be sent in the logs so that |
| admins are told that there's something to be done. |
| |
| |
| 4.6) Customizing errors |
| ----------------------- |
| Some situations can make haproxy return an HTTP error code to the client : |
| - invalid or too long request => HTTP 400 |
| - request not completely sent in time => HTTP 408 |
| - forbidden request (matches a deny filter) => HTTP 403 |
| - internal error in haproxy => HTTP 500 |
| - the server returned an invalid or incomplete response => HTTP 502 |
| - no server was available to handle the request => HTTP 503 |
| - the server failed to reply in time => HTTP 504 |
| |
| A succint error message taken from the RFC accompanies these return codes. |
| But depending on the clients knowledge, it may be better to return custom, user |
| friendly, error pages. This is made possible in two ways, one involving a |
| redirection to a known server, and another one consisting in returning a local |
| file. |
| |
| 4.6.1) Relocation |
| ----------------- |
| An error relocation is achieved using the 'errorloc' command : |
| |
| errorloc <HTTP_code> <location> |
| |
| Instead of generating an HTTP error <HTTP_code> among those above, the proxy |
| will return a temporary redirection code (HTTP 302) towards the address |
| specified in <location>. This address may be either relative to the site or |
| absolute. Since this request will be handled by the client's browser, it's |
| mandatory that the returned address be reachable from the outside. |
| |
| Example : |
| --------- |
| listen application 0.0.0.0:80 |
| errorloc 400 /badrequest.html |
| errorloc 403 /forbidden.html |
| errorloc 408 /toolong.html |
| errorloc 500 http://haproxy.domain.net/bugreport.html |
| errorloc 502 http://192.168.114.58/error50x.html |
| errorloc 503 http://192.168.114.58/error50x.html |
| errorloc 504 http://192.168.114.58/error50x.html |
| |
| Note: RFC2616 says that a client must reuse the same method to fetch the |
| Location returned by a 302, which causes problems with the POST method. |
| The return code 303 was designed explicitly to force the client to fetch the |
| Location URL with the GET method, but there are some browsers pre-dating |
| HTTP/1.1 which don't support it. Anyway, most browsers still behave with 302 as |
| if it was a 303. In order to allow the user to chose, versions 1.1.31 and 1.2.5 |
| bring two new keywords to replace 'errorloc' : 'errorloc302' and 'errorloc303'. |
| |
| They are preffered over errorloc (which still does 302). Consider using |
| errorloc303 everytime you know that your clients support HTTP 303 responses.. |
| |
| 4.6.2) Local files |
| ------------------ |
| Sometimes, it is desirable to change the returned error without resorting to |
| redirections. The second method consists in loading local files during startup |
| and send them as pure HTTP content upon error. This is what the 'errorfile' |
| keyword does. |
| |
| Warning, there are traps to consider : |
| - The files are loaded while parsing configuration, before doing a chroot(). |
| Thus, they are relative to the real filesystem. For this reason, it is |
| recommended to pass an absolute path to those files. |
| |
| - The contents of those files is not HTML, but real HTTP protocol with |
| possible HTML body. So the first line and headers are mandatory. Ideally, |
| every line in the HTTP part should end with CR-LF for maximum compatibility. |
| |
| - The response is limited to the buffer size (BUSIZE), generally 8 or 16 kB. |
| |
| - The response should not include references to the local server, in order to |
| avoid infinite loops on the browser in case of local failure. |
| |
| Example : |
| --------- |
| errorfile 400 /etc/haproxy/errorfiles/400badreq.http |
| errorfile 403 /etc/haproxy/errorfiles/403forbid.http |
| errorfile 503 /etc/haproxy/errorfiles/503sorry.http |
| |
| |
| 4.7) Modifying default values |
| ----------------------------- |
| Version 1.1.22 introduced the notion of default values, which eliminates the |
| pain of often repeating common parameters between many instances, such as |
| logs, timeouts, modes, etc... |
| |
| Default values are set in a 'defaults' section. Each of these section clears |
| all previously set default parameters, so there may be as many default |
| parameters as needed. Only the last one before a 'listen' section will be |
| used for this section. The 'defaults' section uses the same syntax as the |
| 'listen' section, for the supported parameters. The 'defaults' keyword ignores |
| everything on its command line, so that fake instance names can be specified |
| there for better clarity. |
| |
| In version 1.1.28/1.2.1, only those parameters can be preset in the 'default' |
| section : |
| - log (the first and second one) |
| - mode { tcp, http, health } |
| - balance { roundrobin } |
| - disabled (to disable every further instances) |
| - enabled (to enable every further instances, this is the default) |
| - contimeout, clitimeout, srvtimeout, grace, retries, maxconn |
| - option { redispatch, transparent, keepalive, forwardfor, logasap, httpclose, |
| checkcache, httplog, tcplog, dontlognull, persist, httpchk } |
| - redispatch, redisp, transparent, source { addr:port } |
| - cookie, capture |
| - errorloc |
| |
| As of 1.1.24, it is not possible to put certain parameters in a 'defaults' |
| section, mainly regular expressions and server configurations : |
| - dispatch, server, |
| - req*, rsp* |
| |
| Last, there's no way yet to change a boolean option from its assigned default |
| value. So if an 'option' statement is set in a 'defaults' section, the only |
| way to flush it is to redefine a new 'defaults' section without this 'option'. |
| |
| Examples : |
| ---------- |
| defaults applications TCP |
| log global |
| mode tcp |
| balance roundrobin |
| clitimeout 180000 |
| srvtimeout 180000 |
| contimeout 4000 |
| retries 3 |
| redispatch |
| |
| listen app_tcp1 10.0.0.1:6000-6063 |
| server srv1 192.168.1.1 check port 6000 inter 10000 |
| server srv2 192.168.1.2 backup |
| |
| listen app_tcp2 10.0.0.2:6000-6063 |
| server srv1 192.168.2.1 check port 6000 inter 10000 |
| server srv2 192.168.2.2 backup |
| |
| defaults applications HTTP |
| log global |
| mode http |
| option httplog |
| option forwardfor |
| option dontlognull |
| balance roundrobin |
| clitimeout 20000 |
| srvtimeout 20000 |
| contimeout 4000 |
| retries 3 |
| |
| listen app_http1 10.0.0.1:80-81 |
| cookie SERVERID postonly insert indirect |
| capture cookie userid= len 10 |
| server srv1 192.168.1.1:+8000 cookie srv1 check port 8080 inter 1000 |
| server srv1 192.168.1.2:+8000 cookie srv2 check port 8080 inter 1000 |
| |
| defaults |
| # this empty section voids all default parameters |
| |
| |
| 4.8) Status report in HTML page |
| ------------------------------- |
| Starting with 1.2.14, it is possible for HAProxy to intercept requests for a |
| particular URI and return a full report of the proxy's activity and servers |
| statistics. This is available through the 'stats' keyword, associated to any |
| such options : |
| |
| - stats enable |
| - stats uri <uri prefix> |
| - stats realm <authentication realm> |
| - stats auth <user:password> |
| - stats scope <proxy_id> | '.' |
| |
| By default, the status report is disabled. Specifying any combination above |
| enables it for the proxy instance referencing it. The easiest solution is to |
| use "stats enable" which will enable the report with default parameters : |
| |
| - default URI : "/haproxy?stats" (CONFIG_STATS_DEFAULT_URI) |
| - default auth : unspecified (no authentication) |
| - default realm : "HAProxy Statistics" (CONFIG_STATS_DEFAULT_REALM) |
| - default scope : unspecified (access to all instances) |
| |
| The "stats uri <uri_prefix>" option allows one to intercept another URI prefix. |
| Note that any URI that BEGINS with this string will match. For instance, one |
| proxy instance might be dedicated to status page only and would reply to any |
| URI. |
| |
| Example : |
| --------- |
| # catches any URI and returns the status page. |
| listen stats :8080 |
| mode http |
| stats uri / |
| |
| The "stats auth <user:password>" option enables Basic authentication and adds a |
| valid user:password combination to the list of authorized accounts. The user |
| and password are passed in the configuration file as clear text, and since this |
| is HTTP Basic authentication, you should be aware that it transits as clear |
| text on the network, so you must not use any sensible account. The list is |
| unlimited in order to provide easy accesses to developpers or customers. |
| |
| The "stats realm <realm>" option defines the "realm" name which is displayed |
| in the popup box when the browser asks for a password. It's important to ensure |
| that this one is not used by the application, otherwise the browser will try to |
| use a cached one from the application. Note that any space in the realm name |
| should be escaped with a backslash ('\'). |
| |
| The "stats scope <proxy_id>" option limits the scope of the status report. By |
| default, all proxy instances are listed. But under some circumstances, it would |
| be better to limit the listing to some proxies or only to the current one. This |
| is what this option does. The special proxy name "." (a single dot) references |
| the current proxy. The proxy name can be repeated multiple times, even for |
| proxies defined later in the configuration or some which do not exist. The name |
| is the one which appears after the 'listen' keyword. |
| |
| Example : |
| --------- |
| # simple application with authenticated embedded status report |
| listen app1 192.168.1.100:80 |
| mode http |
| option httpclose |
| balance roundrobin |
| cookie SERVERID postonly insert indirect |
| server srv1 192.168.1.1:8080 cookie srv1 check inter 1000 |
| server srv1 192.168.1.2:8080 cookie srv2 check inter 1000 |
| stats uri /my_stats |
| stats realm Statistics\ for\ MyApp1-2 |
| stats auth guest:guest |
| stats auth admin:AdMiN123 |
| stats scope . |
| stats scope app2 |
| |
| # simple application with anonymous embedded status report |
| listen app2 192.168.2.100:80 |
| mode http |
| option httpclose |
| balance roundrobin |
| cookie SERVERID postonly insert indirect |
| server srv1 192.168.2.1:8080 cookie srv1 check inter 1000 |
| server srv1 192.168.2.2:8080 cookie srv2 check inter 1000 |
| stats uri /my_stats |
| stats realm Statistics\ for\ MyApp2 |
| stats scope . |
| |
| listen admin_page :8080 |
| mode http |
| stats uri /my_stats |
| stats realm Global\ statistics |
| stats auth admin:AdMiN123 |
| |
| Notes : |
| ------- |
| - The 'stats' options can also be specified in the 'defaults' section, in |
| which case it will provide the exact same configuration to all further |
| instances (hence the usefulness of the scope "."). However, if an instance |
| redefines any 'stats' parameter, defaults will not be used for this |
| instance. |
| |
| - HTTP Basic authentication is very basic and unsecure from snooping. No |
| sensible password should be used, and be aware that there is no way to |
| remove it from the browser so it will be sent to the whole application |
| upon further accesses. |
| |
| - It is very important that the 'option httpclose' is specified, otherwise |
| the proxy will not be able to detect the URI within keep-alive sessions |
| maintained between the browser and the servers, so the stats URI will be |
| forwarded unmodified to the server as if the option was not set. |
| |
| |
| 5) Access lists |
| =============== |
| |
| With version 1.3.10, a new concept of access lists (acl) was born. As it was |
| not necesary to reinvent the wheel, and because even long thoughts lead to |
| unsatisfying proposals, it was finally decided that something close to what |
| Squid provides would be a good compromise between features and ease of use. |
| |
| The principle is very simple : acls are declared with a name, a test and a list |
| of valid values to check against during the test. Conditions are applied on |
| various actions, and those conditions apply a logical AND between acls. The |
| condition is then only met if all acls are true. |
| |
| It is possible to use the reserved keyword "OR" in conditions, and it is |
| possible for an acl to be specified multiple times, even with various tests, in |
| which case the first one which returns true validates the ACL. |
| |
| As of 1.3.12, only the following tests have been implemented : |
| |
| Layer 3/4 : |
| src <ipv4_address>[/mask] ... : match IPv4 source address |
| dst <ipv4_address>[/mask] ... : match IPv4 destination address |
| src_port <range> ... : match source port range |
| dst_port <range> ... : match destination port range |
| dst_conn <range> ... : match #connections on frontend |
| |
| Layer 7 : |
| method <HTTP method> ... : match HTTP method |
| req_ver <1.0|1.1> ... : match HTTP request version |
| resp_ver <1.0|1.1> ... : match HTTP response version |
| status <range> ... : match HTTP response status code in range |
| url <string> ... : exact string match on URI |
| url_reg <regex> ... : regex string match on URI |
| url_beg <string> ... : true if URI begins with <string> |
| url_end <string> ... : true if URI ends with <string> |
| url_sub <string> ... : true if URI contains <string> |
| url_dir <string> ... : true if URI contains <string> between slashes |
| url_dom <string> ... : true if URI contains <string> between slashes or dots |
| |
| A 'range' is one or two integers which may be prefixed by an operator. |
| The syntax is : |
| |
| [<op>] <low>[:<high>] |
| |
| Where <op> can be : |
| 'eq' : the tested value must be equal to <low> or within <low>..<high> |
| 'le' : the tested value must be lower than or equal to <low> |
| 'lt' : the tested value must be lower than <low> |
| 'ge' : the tested value must be greater than or equal to <low> |
| 'gt' : the tested value must be greater than <low> |
| |
| When no operator is defined, 'eq' is assumed. Note that when the operator is |
| specified, it applies to all subsequent ranges of values until the end of the |
| line is reached or another operator is specified. Example : |
| |
| acl status_error status 400:599 |
| acl saturated_frt dst_conn ge 1000 |
| acl invalid_ports src_port lt 512 ge 65535 |
| |
| Other ones are coming (headers, cookies, time, auth), it's just a matter of |
| time. It is also planned to be able to read the patterns from a file, as well |
| as to ignore the case for some of them. |
| |
| The only command supporting a condition right now is the "block" command, which |
| blocks a request and returns a 403 if its condition is true (with the "if" |
| keyword), or if it is false (with the "unless" keyword). |
| |
| Example : |
| --------- |
| |
| acl options_uris url * |
| acl meth_option method OPTIONS |
| acl http_1.1 req_ver 1.1 |
| acl allowed_meth method GET HEAD POST OPTIONS CONNECT |
| acl connect_meth method CONNECT |
| acl proxy_url url_beg http:// |
| |
| # block if reserved URI "*" used with a method other than "OPTIONS" |
| block if options_uris !meth_option |
| |
| # block if the OPTIONS method is used with HTTP 1.0 |
| block if meth_option !http_1.1 |
| |
| # allow non-proxy url with anything but the CONNECT method |
| block if !connect_meth !proxy_url |
| |
| # block all unknown methods |
| block unless allowed_meth |
| |
| Note: this documentation is very light but should permit one to start and above |
| all it should permit to work on the project without being slowed down too much |
| with the doc. |
| |
| |
| ========================= |
| | System-specific setup | |
| ========================= |
| |
| Linux 2.4 |
| ========= |
| |
| -- cut here -- |
| #!/bin/sh |
| # set this to about 256/4M (16384 for 256M machine) |
| MAXFILES=16384 |
| echo $MAXFILES > /proc/sys/fs/file-max |
| ulimit -n $MAXFILES |
| |
| if [ -e /proc/sys/net/ipv4/ip_conntrack_max ]; then |
| echo 65536 > /proc/sys/net/ipv4/ip_conntrack_max |
| fi |
| |
| if [ -e /proc/sys/net/ipv4/netfilter/ip_ct_tcp_timeout_fin_wait ]; then |
| # 30 seconds for fin, 15 for time wait |
| echo 3000 > /proc/sys/net/ipv4/netfilter/ip_ct_tcp_timeout_fin_wait |
| echo 1500 > /proc/sys/net/ipv4/netfilter/ip_ct_tcp_timeout_time_wait |
| echo 0 > /proc/sys/net/ipv4/netfilter/ip_ct_tcp_log_invalid_scale |
| echo 0 > /proc/sys/net/ipv4/netfilter/ip_ct_tcp_log_out_of_window |
| fi |
| |
| echo 1024 60999 > /proc/sys/net/ipv4/ip_local_port_range |
| echo 30 > /proc/sys/net/ipv4/tcp_fin_timeout |
| echo 4096 > /proc/sys/net/ipv4/tcp_max_syn_backlog |
| echo 262144 > /proc/sys/net/ipv4/tcp_max_tw_buckets |
| echo 262144 > /proc/sys/net/ipv4/tcp_max_orphans |
| echo 300 > /proc/sys/net/ipv4/tcp_keepalive_time |
| echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle |
| echo 0 > /proc/sys/net/ipv4/tcp_timestamps |
| echo 0 > /proc/sys/net/ipv4/tcp_ecn |
| echo 1 > /proc/sys/net/ipv4/tcp_sack |
| echo 0 > /proc/sys/net/ipv4/tcp_dsack |
| |
| # auto-tuned on 2.4 |
| #echo 262143 > /proc/sys/net/core/rmem_max |
| #echo 262143 > /proc/sys/net/core/rmem_default |
| |
| echo 16384 65536 524288 > /proc/sys/net/ipv4/tcp_rmem |
| echo 16384 349520 699040 > /proc/sys/net/ipv4/tcp_wmem |
| |
| -- cut here -- |
| |
| |
| FreeBSD |
| ======= |
| |
| A FreeBSD port of HA-Proxy is now available and maintained, thanks to |
| Clement Laforet <sheepkiller@cultdeadsheep.org>. |
| |
| For more information : |
| http://www.freebsd.org/cgi/url.cgi?ports/net/haproxy/pkg-descr |
| http://www.freebsd.org/cgi/cvsweb.cgi/ports/net/haproxy/ |
| http://www.freshports.org/net/haproxy |
| |
| |
| -- end -- |