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d2edea1154
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93835 13f79535-47bb-0310-9956-ffa450edef68
210 lines
7.7 KiB
XML
210 lines
7.7 KiB
XML
<?xml version="1.0"?>
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<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
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<?xml-stylesheet type="text/xsl" href="../style/manual.xsl"?>
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<modulesynopsis>
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<name>prefork</name>
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<description>Implements a non-threaded, pre-forking web server</description>
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<status>MPM</status>
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<sourcefile>prefork.c</sourcefile>
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<identifier>mpm_prefork_module</identifier>
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<summary>
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<p>This Multi-Processing Module (MPM) implements a
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non-threaded, pre-forking web server which handles request in a
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manner very similar to the default behavior of Apache 1.3 on
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Unix.</p>
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<p>A single control process is responsible for launching child
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processes which listen for connections and serve them when they
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arrive. Apache always tries to maintain several <em>spare</em>
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or idle server processes, which stand ready to serve incoming
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requests. In this way, clients do not need to wait for a new
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child processes to be forked before their requests can be
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served.</p>
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<p>The <directive module="mpm_common">StartServers</directive>,
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<directive module="prefork">MinSpareServers</directive>,
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<directive module="prefork">MaxSpareServers</directive>, and
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<directive module="mpm_common">MaxClients</directive> regulate how
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the parent process creates children to serve requests. In general,
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Apache is very self-regulating, so most sites do not need to
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adjust these directives from their default values. Sites which
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need to serve more than 256 simultaneous requests may need to
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increase <directive module="mpm_common">MaxClients</directive>,
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while sites with limited memory may need to decrease <directive
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module="mpm_common">MaxClients</directive> to keep the server from
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thrashing (swapping memory to disk and back). More information
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about tuning process creation is provided in the <a
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href="../misc/perf-tuning.html">performance hints</a>
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documentation.</p>
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<p>While the parent process is usually started as root under Unix
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in order to bind to port 80, the child processes are launched by
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Apache as a less-privileged user. The <directive
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module="mpm_common">User</directive> and <directive
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module="mpm_common">Group</directive> directives are used to set
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the privileges of the Apache child processes. The child processes
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must be able to read all the content that will be served, but
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should have as few privileges beyond that as possible. In
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addition, unless <a href="../suexec.html">suexec</a> is used,
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these directives also set the privileges which will be inherited
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by CGI scripts.</p>
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<p><directive module="mpm_common">MaxRequestsPerChild</directive>
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controls how frequently the server recycles processes by killing
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old ones and launching new ones.</p>
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</summary>
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<seealso><a href="../bind.html">Setting which addresses and
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ports Apache uses</a></seealso>
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<directivesynopsis location="mpm_common">
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<name>CoreDumpDirectory</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>PidFile</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>Listen</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>ListenBacklog</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>LockFile</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>MaxRequestsPerChild</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>MaxSpareServers</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>MinSpareServers</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>ScoreBoardFile</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>SendBufferSize</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>ServerLimit</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>StartServers</name>
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</directivesynopsis>
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<directivesynopsis location="mpm_common">
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<name>User</name>
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</directivesynopsis>
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<directivesynopsis>
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<name>AcceptMutex</name>
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<description>Method that Apache uses to serialize multiple children
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accepting requests on network sockets</description>
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<syntax>AcceptMutex default|<em>method</em></syntax>
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<default>AcceptMutex default</default>
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<contextlist><context>server config</context></contextlist>
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<usage>
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<p>The <directive>AcceptMutex</directive> directives sets the
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method that Apache uses to serialize multiple children accepting
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requests on network sockets. Prior to Apache 2.0, the method was
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selectable only at compile time. The optimal method to use is
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highly architecture and platform dependent. For further details,
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see the <a href="../misc/perf-tuning.html">performance tuning</a>
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documentation.</p>
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<p>If this directive is set to <code>default</code>, then the
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compile-time selected default will be used. Other possible
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methods are listed below. Note that not all methods are
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available on all platforms. If a method is specified which is
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not available, a message will be written to the error log
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listing the available methods.</p>
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<dl>
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<dt><code>flock</code></dt>
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<dd>uses the <code>flock(2)</code> system call to lock the
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file defined by the <directive module="mpm_common"
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>LockFile</directive> directive.</dd>
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<dt><code>fcntl</code></dt>
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<dd>uses the <code>fnctl(2)</code> system call to lock the
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file defined by the <directive module="mpm_common"
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>LockFile</directive> directive.</dd>
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<dt><code>sysvsem</code></dt>
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<dd>uses SySV-style semaphores to implement the mutex.</dd>
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<dt><code>pthread</code></dt>
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<dd>uses POSIX mutexes as implemented by the POSIX Threads
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(PThreads) specification.</dd>
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</dl>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>MaxSpareServers</name>
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<description>Maximum number of idle child server processes</description>
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<syntax>MaxSpareServers <em>number</em><br /></syntax>
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<default>MaxSpareServers 10</default>
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<contextlist><context>server config</context></contextlist>
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<usage>
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<p>The <directive>MaxSpareServers</directive> directive sets the
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desired maximum number of <em>idle</em> child server processes. An
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idle process is one which is not handling a request. If there are
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more than MaxSpareServers idle, then the parent process will kill
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off the excess processes.</p>
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<p>Tuning of this parameter should only be necessary on very
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busy sites. Setting this parameter to a large number is almost
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always a bad idea.</p>
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</usage>
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<seealso><directive module="prefork">MinSpareServers</directive></seealso>
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<seealso><directive module="mpm_common">StartServers</directive></seealso>
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</directivesynopsis>
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<directivesynopsis>
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<name>MinSpareServers</name>
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<description>Minimum number of idle child server processes</description>
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<syntax>MinSpareServers <em>number</em></syntax>
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<default>MinSpareServers 5</default>
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<contextlist><context>server config</context></contextlist>
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<usage>
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<p>The <directive>MinSpareServers</directive> directive sets the
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desired minimum number of <em>idle</em> child server processes. An
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idle process is one which is not handling a request. If there are
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fewer than MinSpareServers idle, then the parent process creates
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new children at a maximum rate of 1 per second.</p>
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<p>Tuning of this parameter should only be necessary on very
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busy sites. Setting this parameter to a large number is almost
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always a bad idea.</p>
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<p>This directive has no effect on Microsoft Windows.</p>
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</usage>
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<seealso><directive module="prefork">MaxSpareServers</directive></seealso>
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<seealso><directive module="mpm_common">StartServers</directive></seealso>
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</directivesynopsis>
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</modulesynopsis>
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