1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 5 This file is generated from xml source: DO NOT EDIT 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 --> 8<title>prefork - Apache HTTP Server</title> 9<link href="/style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 10<link href="/style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 11<link href="/style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="/style/css/prettify.css" /> 12<script src="/style/scripts/prettify.js" type="text/javascript"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body> 17<div id="page-header"> 18<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p> 19<p class="apache">Apache HTTP Server Version 2.2</p> 20<img alt="" src="/images/feather.gif" /></div> 21<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 22<div id="path"> 23<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 2.2</a> > <a href="./">Modules</a></div> 24<div id="page-content"> 25<div id="preamble"><h1>Apache MPM prefork</h1> 26<div class="toplang"> 27<p><span>Available Languages: </span><a href="/de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | 28<a href="/en/mod/prefork.html" title="English"> en </a> | 29<a href="/ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 30<a href="/tr/mod/prefork.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 31</div> 32<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> 33<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr> 34<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>mpm_prefork_module</td></tr> 35<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>prefork.c</td></tr></table> 36<h3>Summary</h3> 37 38 <p>This Multi-Processing Module (MPM) implements a non-threaded, 39 pre-forking web server that handles requests in a manner similar 40 to Apache 1.3. It is appropriate for sites that need to avoid 41 threading for compatibility with non-thread-safe libraries. It 42 is also the best MPM for isolating each request, so that a problem 43 with a single request will not affect any other.</p> 44 45 <p>This MPM is very self-regulating, so it is rarely necessary to 46 adjust its configuration directives. Most important is that 47 <code class="directive"><a href="/mod/mpm_common.html#maxclients">MaxClients</a></code> be big enough to 48 handle as many simultaneous requests as you expect to receive, but 49 small enough to assure that there is enough physical RAM for all 50 processes.</p> 51</div> 52<div id="quickview"><h3 class="directives">Directives</h3> 53<ul id="toc"> 54<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#acceptmutex">AcceptMutex</a></li> 55<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li> 56<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li> 57<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#group">Group</a></li> 58<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li> 59<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li> 60<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#lockfile">LockFile</a></li> 61<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li> 62<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li> 63<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li> 64<li><img alt="" src="/images/down.gif" /> <a href="#maxspareservers">MaxSpareServers</a></li> 65<li><img alt="" src="/images/down.gif" /> <a href="#minspareservers">MinSpareServers</a></li> 66<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li> 67<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#receivebuffersize">ReceiveBufferSize</a></li> 68<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li> 69<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li> 70<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li> 71<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li> 72<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#user">User</a></li> 73</ul> 74<h3>Topics</h3> 75<ul id="topics"> 76<li><img alt="" src="/images/down.gif" /> <a href="#how-it-works">How it Works</a></li> 77</ul><h3>See also</h3> 78<ul class="seealso"> 79<li><a href="/bind.html">Setting which addresses and ports Apache 80uses</a></li> 81</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 82<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 83<div class="section"> 84<h2><a name="how-it-works" id="how-it-works">How it Works</a></h2> 85 <p>A single control process is responsible for launching child 86 processes which listen for connections and serve them when they 87 arrive. Apache always tries to maintain several <dfn>spare</dfn> 88 or idle server processes, which stand ready to serve incoming 89 requests. In this way, clients do not need to wait for a new 90 child processes to be forked before their requests can be 91 served.</p> 92 93 <p>The <code class="directive"><a href="/mod/mpm_common.html#startservers">StartServers</a></code>, 94 <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, 95 <code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code>, and 96 <code class="directive"><a href="/mod/mpm_common.html#maxclients">MaxClients</a></code> regulate how 97 the parent process creates children to serve requests. In general, 98 Apache is very self-regulating, so most sites do not need to 99 adjust these directives from their default values. Sites which 100 need to serve more than 256 simultaneous requests may need to 101 increase <code class="directive"><a href="/mod/mpm_common.html#maxclients">MaxClients</a></code>, 102 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 103 thrashing (swapping memory to disk and back). More information 104 about tuning process creation is provided in the <a href="/misc/perf-tuning.html">performance hints</a> 105 documentation.</p> 106 107 <p>While the parent process is usually started as <code>root</code> 108 under Unix in order to bind to port 80, the child processes are 109 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 110 the privileges of the Apache child processes. The child processes 111 must be able to read all the content that will be served, but 112 should have as few privileges beyond that as possible.</p> 113 114 <p><code class="directive"><a href="/mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code> 115 controls how frequently the server recycles processes by killing 116 old ones and launching new ones.</p> 117</div> 118<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 119<div class="directive-section"><h2><a name="MaxSpareServers" id="MaxSpareServers">MaxSpareServers</a> <a name="maxspareservers" id="maxspareservers">Directive</a></h2> 120<table class="directive"> 121<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle child server processes</td></tr> 122<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareServers <var>number</var></code></td></tr> 123<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxSpareServers 10</code></td></tr> 124<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 125<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 126<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr> 127</table> 128 <p>The <code class="directive">MaxSpareServers</code> directive sets the 129 desired maximum number of <em>idle</em> child server processes. An 130 idle process is one which is not handling a request. If there are 131 more than <code class="directive">MaxSpareServers</code> idle, then the 132 parent process will kill off the excess processes.</p> 133 134 <p>Tuning of this parameter should only be necessary on very 135 busy sites. Setting this parameter to a large number is almost 136 always a bad idea. If you are trying to set the value equal to or lower than 137 <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, Apache 138 will automatically adjust it to <code class="directive">MinSpareServers</code><code> + 1</code>.</p> 139 140<h3>See also</h3> 141<ul> 142<li><code class="directive"><a href="#minspareservers">MinSpareServers</a></code></li> 143<li><code class="directive"><a href="/mod/mpm_common.html#startservers">StartServers</a></code></li> 144</ul> 145</div> 146<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 147<div class="directive-section"><h2><a name="MinSpareServers" id="MinSpareServers">MinSpareServers</a> <a name="minspareservers" id="minspareservers">Directive</a></h2> 148<table class="directive"> 149<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle child server processes</td></tr> 150<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareServers <var>number</var></code></td></tr> 151<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MinSpareServers 5</code></td></tr> 152<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 153<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr> 154<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr> 155</table> 156 <p>The <code class="directive">MinSpareServers</code> directive sets the 157 desired minimum number of <em>idle</em> child server processes. An 158 idle process is one which is not handling a request. If there are 159 fewer than <code class="directive">MinSpareServers</code> idle, then the parent 160 process creates new children at a maximum rate of 1 per second.</p> 161 162 <p>Tuning of this parameter should only be necessary on very 163 busy sites. Setting this parameter to a large number is almost 164 always a bad idea.</p> 165 166<h3>See also</h3> 167<ul> 168<li><code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code></li> 169<li><code class="directive"><a href="/mod/mpm_common.html#startservers">StartServers</a></code></li> 170</ul> 171</div> 172</div> 173<div class="bottomlang"> 174<p><span>Available Languages: </span><a href="/de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | 175<a href="/en/mod/prefork.html" title="English"> en </a> | 176<a href="/ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 177<a href="/tr/mod/prefork.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 178</div><div class="top"><a href="#page-header"><img src="/images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div> 179<script type="text/javascript"><!--//--><![CDATA[//><!-- 180var comments_shortname = 'httpd'; 181var comments_identifier = 'http://httpd.apache.org/docs/2.2/mod/prefork.html'; 182(function(w, d) { 183 if (w.location.hostname.toLowerCase() == "httpd.apache.org") { 184 d.write('<div id="comments_thread"><\/div>'); 185 var s = d.createElement('script'); 186 s.type = 'text/javascript'; 187 s.async = true; 188 s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier; 189 (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s); 190 } 191 else { 192 d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>'); 193 } 194})(window, document); 195//--><!]]></script></div><div id="footer"> 196<p class="apache">Copyright 2013 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> 197<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!-- 198if (typeof(prettyPrint) !== 'undefined') { 199 prettyPrint(); 200} 201//--><!]]></script> 202</body></html>
