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bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<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>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<p class="apache">Apache HTTP Server Version 2.3</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div>
70953fb44a7140fe206c3a5f011e24209c8c5c6abnicholes<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <a href="./">Modules</a></div>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<p><span>Available Languages: </span><a href="/de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<a href="/en/mod/prefork.html" title="English"> en </a> |
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bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Implements a non-threaded, pre-forking web server</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>mpm_prefork_module</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>prefork.c</td></tr></table>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>This Multi-Processing Module (MPM) implements a non-threaded,
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes pre-forking web server that handles requests in a manner similar
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes to Apache 1.3. It is appropriate for sites that need to avoid
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes threading for compatibility with non-thread-safe libraries. It
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes is also the best MPM for isolating each request, so that a problem
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes with a single request will not affect any other.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>This MPM is very self-regulating, so it is rarely necessary to
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes adjust its configuration directives. Most important is that
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <code class="directive"><a href="/mod/mpm_common.html#maxclients">MaxClients</a></code> be big enough to
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes handle as many simultaneous requests as you expect to receive, but
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes small enough to assure that there is enough physical RAM for all
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes processes.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<div id="quickview"><h3 class="directives">Directives</h3>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mod_unixd.html#group">Group</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li>
ac7985784d08a3655291f24f711812b4d8b1cbcffuankg<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/down.gif" /> <a href="#maxspareservers">MaxSpareServers</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/down.gif" /> <a href="#minspareservers">MinSpareServers</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#receivebuffersize">ReceiveBufferSize</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/right.gif" /> <a href="mod_unixd.html#user">User</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><img alt="" src="/images/down.gif" /> <a href="#how-it-works">How it Works</a></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><a href="/bind.html">Setting which addresses and ports Apache
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<h2><a name="how-it-works" id="how-it-works">How it Works</a></h2>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>A single control process is responsible for launching child
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes processes which listen for connections and serve them when they
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes arrive. Apache always tries to maintain several <dfn>spare</dfn>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes or idle server processes, which stand ready to serve incoming
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes requests. In this way, clients do not need to wait for a new
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes child processes to be forked before their requests can be
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>The <code class="directive"><a href="/mod/mpm_common.html#startservers">StartServers</a></code>,
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>,
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code>, and
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <code class="directive"><a href="/mod/mpm_common.html#maxclients">MaxClients</a></code> regulate how
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes the parent process creates children to serve requests. In general,
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes Apache is very self-regulating, so most sites do not need to
ac7985784d08a3655291f24f711812b4d8b1cbcffuankg adjust these directives from their default values. Sites which
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes need to serve more than 256 simultaneous requests may need to
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes increase <code class="directive"><a href="/mod/mpm_common.html#maxclients">MaxClients</a></code>,
ac7985784d08a3655291f24f711812b4d8b1cbcffuankg while sites with limited memory may need to decrease <code class="directive"><a href="/mod/mpm_common.html#maxclients">MaxClients</a></code> to keep the server from
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes thrashing (swapping memory to disk and back). More information
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes about tuning process creation is provided in the <a href="/misc/perf-tuning.html">performance hints</a>
0a39e7683f6611d66c55712f50bb240428d832a1bnicholes documentation.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>While the parent process is usually started as <code>root</code>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes under Unix in order to bind to port 80, the child processes are
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes launched by Apache as a less-privileged user. The <code class="directive"><a href="/mod/mod_unixd.html#user">User</a></code> and <code class="directive"><a href="/mod/mod_unixd.html#group">Group</a></code> directives are used to set
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes the privileges of the Apache child processes. The child processes
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes must be able to read all the content that will be served, but
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes should have as few privileges beyond that as possible.</p>
ac7985784d08a3655291f24f711812b4d8b1cbcffuankg <p><code class="directive"><a href="/mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code>
0662ed52e814f8f08ef0e09956413a792584eddffuankg controls how frequently the server recycles processes by killing
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes old ones and launching new ones.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>This MPM uses the <code>mpm-accept</code> mutex to serialize
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes access to incoming connections when subject to the thundering herd
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes problem (generally, when there are multiple listening sockets).
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes The implementation aspects of this mutex can be configured with the
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <code class="directive"><a href="/mod/core.html#mutex">Mutex</a></code> directive. The <a href="/misc/perf-tuning.html">performance hints</a>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes documentation has additional information about this mutex.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<div class="directive-section"><h2><a name="MaxSpareServers" id="MaxSpareServers">MaxSpareServers</a> <a name="maxspareservers" id="maxspareservers">Directive</a></h2>
0662ed52e814f8f08ef0e09956413a792584eddffuankg<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle child server processes</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareServers <var>number</var></code></td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxSpareServers 10</code></td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
0662ed52e814f8f08ef0e09956413a792584eddffuankg<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>The <code class="directive">MaxSpareServers</code> directive sets the
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes desired maximum number of <em>idle</em> child server processes. An
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes idle process is one which is not handling a request. If there are
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes more than <code class="directive">MaxSpareServers</code> idle, then the
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes parent process will kill off the excess processes.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>Tuning of this parameter should only be necessary on very
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes busy sites. Setting this parameter to a large number is almost
0662ed52e814f8f08ef0e09956413a792584eddffuankg always a bad idea. If you are trying to set the value equal to or lower than
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, Apache
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes will automatically adjust it to <code class="directive">MinSpareServers</code><code> + 1</code>.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><code class="directive"><a href="#minspareservers">MinSpareServers</a></code></li>
ac7985784d08a3655291f24f711812b4d8b1cbcffuankg<li><code class="directive"><a href="/mod/mpm_common.html#startservers">StartServers</a></code></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<div class="directive-section"><h2><a name="MinSpareServers" id="MinSpareServers">MinSpareServers</a> <a name="minspareservers" id="minspareservers">Directive</a></h2>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle child server processes</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareServers <var>number</var></code></td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MinSpareServers 5</code></td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>The <code class="directive">MinSpareServers</code> directive sets the
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes desired minimum number of <em>idle</em> child server processes. An
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes idle process is one which is not handling a request. If there are
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes fewer than <code class="directive">MinSpareServers</code> idle, then the parent
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes process creates new children at a maximum rate of 1 per second.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes <p>Tuning of this parameter should only be necessary on very
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes busy sites. Setting this parameter to a large number is almost
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes always a bad idea.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<li><code class="directive"><a href="/mod/mpm_common.html#startservers">StartServers</a></code></li>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<p><span>Available Languages: </span><a href="/de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<a href="/en/mod/prefork.html" title="English"> en </a> |
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<a href="/ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<a href="/tr/mod/prefork.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
bb2b38cd44b032118359afbc743efbea12f48e61bnicholes<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>