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9.2 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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This file is generated from xml source: DO NOT EDIT
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--><title>worker - Apache HTTP Server</title><link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /><link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /><link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link href="../images/favicon.ico" rel="shortcut icon" /></head><body><div id="page-header"><p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p><p class="apache">Apache HTTP Server Version 2.0</p><img alt="" src="../images/feather.gif" /></div><div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div><div id="path"><a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a> > <a href="./">Modules</a></div><div id="page-content"><div id="preamble"><h1>Apache Module worker</h1><table class="module"><tr><th><a href="module-dict.html#Description">Description:
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</a></th><td>Multi-Processing Module implementing a hybrid
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multi-threaded multi-process web server</td></tr><tr><th><a href="module-dict.html#Status">Status:
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</a></th><td>MPM</td></tr><tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:
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</a></th><td>mpm_worker_module</td></tr><tr><th><a href="module-dict.html#SourceFile">Source File:
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</a></th><td>worker.c</td></tr></table><h3>Summary</h3>
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<p>This Multi-Processing Module (MPM) implements a hybrid
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multi-process multi-threaded server. By using threads to serve
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requests, it is able to serve a large number of requests with
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less system resources than a process-based server. Yet it
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retains much of the stability of a process-based server by
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keeping multiple processes available, each with many threads.</p>
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<p>The most important directives used to control this MPM are
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<code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code>, which
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controls the number of threads deployed by each child process and
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<code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>, which
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controls the maximum total number of threads that may be
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launched.</p>
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</div><div id="quickview"><h3 class="directives">Directives</h3><ul id="toc"><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#group">Group</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#lockfile">LockFile</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxsparethreads">MaxSpareThreads</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#minsparethreads">MinSpareThreads</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#threadlimit">ThreadLimit</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#threadsperchild">ThreadsPerChild</a></li>
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<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#user">User</a></li>
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</ul><h3>Topics</h3><ul id="topics"><li><img alt="" src="../images/down.gif" /> How it Works</li></ul><h3>See also</h3><ul class="seealso"><li><a href="../bind.html">Setting which addresses and
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ports Apache uses</a></li></ul></div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="section"><h2>How it Works</h2>
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<p>Each process has a fixed
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number of threads. The server adjusts to handle load by
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increasing or decreasing the number of processes.</p>
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<p>A single control process is responsible for launching child
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processes. Each child process creates a fixed number of threads as
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specified in the <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> directive. The
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individual threads then listen for connections and serve them when
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they arrive.</p>
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<p>Apache always tries to maintain a pool of <em>spare</em> or
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idle server threads, 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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threads or processes to be created before their requests can be
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served. The number of processes that will initially launched is
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set by the <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>
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directive. Then during operation, Apache assesses the total number
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of idle threads in all processes, and forks or kills processes to
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keep this number within the boundaries specified by <code class="directive"><a href="../mod/mpm_common.html#minsparethreads">MinSpareThreads</a></code> and <code class="directive"><a href="../mod/mpm_common.html#maxsparethreads">MaxSpareThreads</a></code>. Since this
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process is very self-regulating, it is rarely necessary to modify
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these directives from their default values. The maximum number of
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clients that may be served simultaneously (i.e., the maximum total
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number of threads in all processes) is determined by the
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<code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> directive,
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while the maximum number of processes that can be launched is set
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by the <code class="directive"><a href="../mod/mpm_common.html#serverlimit">ServerLimit</a></code>
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directive. <code class="directive"><a href="../mod/mpm_common.html#serverlimit">ServerLimit</a></code>
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multiplied by <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> must be greater
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than or equal to <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code></p>
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<p>A typical configuration of the process-thread controls in
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the <code class="module"><a href="../mod/worker.html">worker</a></code> MPM could look as follows:</p>
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<div class="example"><pre>StartServers 2
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MaxClients 150
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MinSpareThreads 25
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MaxSpareThreads 75
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ThreadsPerChild 25
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ServerLimit 16</pre></div>
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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 and threads are
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launched by Apache as a less-privileged user. The <code class="directive"><a href="../mod/mpm_common.html#user">User</a></code> and <code class="directive"><a href="../mod/mpm_common.html#group">Group</a></code> 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><code class="directive"><a href="../mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code>
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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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</div></div><div id="footer"><p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p><p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div></body></html> |