prefork.xml revision e942c741056732f50da2074b36fe59805d370650
efa4f29a7761c2123557276566f45c9084e734c6patrikj<!DOCTYPE modulesynopsis SYSTEM "/style/modulesynopsis.dtd">
e942c741056732f50da2074b36fe59805d370650slive<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<modulesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<description>Implements a non-threaded, pre-forking web server</description>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>This Multi-Processing Module (MPM) implements a
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive non-threaded, pre-forking web server which handles request in a
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive manner very similar to the default behavior of Apache 1.3 on
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>A single control process is responsible for launching child
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive processes which listen for connections and serve them when they
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive arrive. Apache always tries to maintain several <em>spare</em>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive or idle server processes, which stand ready to serve incoming
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive requests. In this way, clients do not need to wait for a new
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive child processes to be forked before their requests can be
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive served.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>The <directive module="mpm_common">StartServers</directive>,
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <directive module="prefork">MinSpareServers</directive>,
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <directive module="prefork">MaxSpareServers</directive>, and
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <directive module="mpm_common">MaxClients</directive> regulate how
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive the parent process creates children to serve requests. In general,
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive Apache is very self-regulating, so most sites do not need to
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive adjust these directives from their default values. Sites which
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive need to serve more than 256 simultaneous requests may need to
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive increase <directive module="mpm_common">MaxClients</directive>,
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive while sites with limited memory may need to decrease <directive
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive module="mpm_common">MaxClients</directive> to keep the server from
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive thrashing (swapping memory to disk and back). More information
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive about tuning process creation is provided in the <a
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive documentation.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>While the parent process is usually started as root under Unix
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive in order to bind to port 80, the child processes are launched by
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive Apache as a less-privileged user. The <directive
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive module="mpm_common">Group</directive> directives are used to set
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive the privileges of the Apache child processes. The child processes
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive must be able to read all the content that will be served, but
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive should have as few privileges beyond that as possible. In
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive addition, unless <a href="/suexec.html">suexec</a> is used,
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive these directives also set the privileges which will be inherited
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive by CGI scripts.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p><directive module="mpm_common">MaxRequestsPerChild</directive>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive controls how frequently the server recycles processes by killing
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive old ones and launching new ones.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<seealso><a href="/bind.html">Setting which addresses and
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<description>Method that Apache uses to serialize multiple children
fc88db23cb4b205f1efea5f5d5ae916589db5a61sliveaccepting requests on network sockets</description>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<contextlist><context>server config</context></contextlist>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>The <directive>AcceptMutex</directive> directives sets the
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive method that Apache uses to serialize multiple children accepting
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive requests on network sockets. Prior to Apache 2.0, the method was
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive selectable only at compile time. The optimal method to use is
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive highly architecture and platform dependent. For further details,
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive see the <a href="/misc/perf-tuning.html">performance tuning</a>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive documentation.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>If this directive is set to <code>default</code>, then the
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive compile-time selected default will be used. Other possible
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive methods are listed below. Note that not all methods are
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive available on all platforms. If a method is specified which is
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive not available, a message will be written to the error log
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive listing the available methods.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <dd>uses the <code>flock(2)</code> system call to lock the
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <dd>uses the <code>fnctl(2)</code> system call to lock the
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <dd>uses SySV-style semaphores to implement the mutex.</dd>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <dd>uses POSIX mutexes as implemented by the POSIX Threads
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive (PThreads) specification.</dd>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<description>Maximum number of idle child server processes</description>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<contextlist><context>server config</context></contextlist>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>The <directive>MaxSpareServers</directive> directive sets the
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive desired maximum number of <em>idle</em> child server processes. An
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive idle process is one which is not handling a request. If there are
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive more than MaxSpareServers idle, then the parent process will kill
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive off the excess processes.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>Tuning of this parameter should only be necessary on very
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive busy sites. Setting this parameter to a large number is almost
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive always a bad idea.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<seealso><directive module="prefork">MinSpareServers</directive></seealso>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<seealso><directive module="mpm_common">StartServers</directive></seealso>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<description>Minimum number of idle child server processes</description>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<contextlist><context>server config</context></contextlist>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>The <directive>MinSpareServers</directive> directive sets the
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive desired minimum number of <em>idle</em> child server processes. An
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive idle process is one which is not handling a request. If there are
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive fewer than MinSpareServers idle, then the parent process creates
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive new children at a maximum rate of 1 per second.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>Tuning of this parameter should only be necessary on very
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive busy sites. Setting this parameter to a large number is almost
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive always a bad idea.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive <p>This directive has no effect on Microsoft Windows.</p>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<seealso><directive module="prefork">MaxSpareServers</directive></seealso>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive<seealso><directive module="mpm_common">StartServers</directive></seealso>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</directivesynopsis>
fc88db23cb4b205f1efea5f5d5ae916589db5a61slive</modulesynopsis>