rubbos/app/apache2/manual/mod/prefork.html.en

   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" />
  12 <link href="../images/favicon.ico" rel="shortcut icon" /></head>
  13 <body>
  14 <div id="page-header">
  15 <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>
  16 <p class="apache">Apache HTTP Server Version 2.0</p>
  17 <img alt="" src="../images/feather.gif" /></div>
  18 <div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
  19 <div id="path">
  20 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.0</a> &gt; <a href="./">Modules</a></div>
  21 <div id="page-content">
  22 <div id="preamble"><h1>Apache MPM prefork</h1>
  23 <div class="toplang">
  24 <p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
  25 <a href="../en/mod/prefork.html" title="English">&nbsp;en&nbsp;</a> |
  26 <a href="../es/mod/prefork.html" hreflang="es" rel="alternate" title="Español">&nbsp;es&nbsp;</a> |
  27 <a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  28 <a href="../tr/mod/prefork.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
  29 </div>
  30 <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>
  31 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  32 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>mpm_prefork_module</td></tr>
  33 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>prefork.c</td></tr></table>
  34 <h3>Summary</h3>
  35
  36     <p>This Multi-Processing Module (MPM) implements a non-threaded,
  37     pre-forking web server that handles requests in a manner similar
  38     to Apache 1.3.  It is appropriate for sites that need to avoid
  39     threading for compatibility with non-thread-safe libraries.  It
  40     is also the best MPM for isolating each request, so that a problem
  41     with a single request will not affect any other.</p>
  42
  43     <p>This MPM is very self-regulating, so it is rarely necessary to
  44     adjust its configuration directives.  Most important is that
  45     <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> be big enough to
  46     handle as many simultaneous requests as you expect to receive, but
  47     small enough to assure that there is enough physical RAM for all
  48     processes.</p>
  49 </div>
  50 <div id="quickview"><h3 class="directives">Directives</h3>
  51 <ul id="toc">
  52 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#acceptmutex">AcceptMutex</a></li>
  53 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#bs2000account">BS2000Account</a></li>
  54 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
  55 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li>
  56 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#group">Group</a></li>
  57 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li>
  58 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
  59 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#lockfile">LockFile</a></li>
  60 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li>
  61 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li>
  62 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>
  63 <li><img alt="" src="../images/down.gif" /> <a href="#maxspareservers">MaxSpareServers</a></li>
  64 <li><img alt="" src="../images/down.gif" /> <a href="#minspareservers">MinSpareServers</a></li>
  65 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li>
  66 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#receivebuffersize">ReceiveBufferSize</a></li>
  67 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
  68 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
  69 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li>
  70 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li>
  71 <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#user">User</a></li>
  72 </ul>
  73 <h3>Topics</h3>
  74 <ul id="topics">
  75 <li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it Works</a></li>
  76 </ul><h3>See also</h3>
  77 <ul class="seealso">
  78 <li><a href="../bind.html">Setting which addresses and ports Apache
  79 uses</a></li>
  80 </ul></div>
  81 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  82 <div class="section">
  83 <h2><a name="how-it-works" id="how-it-works">How it Works</a></h2>
  84     <p>A single control process is responsible for launching child
  85     processes which listen for connections and serve them when they
  86     arrive. Apache always tries to maintain several <dfn>spare</dfn>
  87     or idle server processes, which stand ready to serve incoming
  88     requests. In this way, clients do not need to wait for a new
  89     child processes to be forked before their requests can be
  90     served.</p>
  91
  92     <p>The <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>,
  93     <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>,
  94     <code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code>, and
  95     <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> regulate how
  96     the parent process creates children to serve requests. In general,
  97     Apache is very self-regulating, so most sites do not need to
  98     adjust these directives from their default values. Sites which
  99     need to serve more than 256 simultaneous requests may need to
 100     increase <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>,
 101     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
 102     thrashing (swapping memory to disk and back). More information
 103     about tuning process creation is provided in the <a href="../misc/perf-tuning.html">performance hints</a>
 104     documentation.</p>
 105
 106     <p>While the parent process is usually started as <code>root</code>
 107     under Unix in order to bind to port 80, the child processes are
 108     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
 109     the privileges of the Apache child processes. The child processes
 110     must be able to read all the content that will be served, but
 111     should have as few privileges beyond that as possible.</p>
 112
 113     <p><code class="directive"><a href="../mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code>
 114     controls how frequently the server recycles processes by killing
 115     old ones and launching new ones.</p>
 116 </div>
 117 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 118 <div class="directive-section"><h2><a name="MaxSpareServers" id="MaxSpareServers">MaxSpareServers</a> <a name="maxspareservers" id="maxspareservers">Directive</a></h2>
 119 <table class="directive">
 120 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle child server processes</td></tr>
 121 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareServers <var>number</var></code></td></tr>
 122 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxSpareServers 10</code></td></tr>
 123 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 124 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 125 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
 126 </table>
 127     <p>The <code class="directive">MaxSpareServers</code> directive sets the
 128     desired maximum number of <em>idle</em> child server processes. An
 129     idle process is one which is not handling a request. If there are
 130     more than <code class="directive">MaxSpareServers</code> idle, then the
 131     parent process will kill off the excess processes.</p>
 132
 133     <p>Tuning of this parameter should only be necessary on very
 134     busy sites. Setting this parameter to a large number is almost
 135     always a bad idea. If you are trying to set the value lower than
 136     <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, Apache
 137     will automatically adjust it to <code class="directive">MinSpareServers</code><code> + 1</code>.</p>
 138
 139 <h3>See also</h3>
 140 <ul>
 141 <li><code class="directive"><a href="#minspareservers">MinSpareServers</a></code></li>
 142 <li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
 143 </ul>
 144 </div>
 145 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 146 <div class="directive-section"><h2><a name="MinSpareServers" id="MinSpareServers">MinSpareServers</a> <a name="minspareservers" id="minspareservers">Directive</a></h2>
 147 <table class="directive">
 148 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle child server processes</td></tr>
 149 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareServers <var>number</var></code></td></tr>
 150 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MinSpareServers 5</code></td></tr>
 151 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 152 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 153 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
 154 </table>
 155     <p>The <code class="directive">MinSpareServers</code> directive sets the
 156     desired minimum number of <em>idle</em> child server processes. An
 157     idle process is one which is not handling a request. If there are
 158     fewer than <code class="directive">MinSpareServers</code> idle, then the parent
 159     process creates new children at a maximum rate of 1 per second.</p>
 160
 161     <p>Tuning of this parameter should only be necessary on very
 162     busy sites. Setting this parameter to a large number is almost
 163     always a bad idea.</p>
 164
 165 <h3>See also</h3>
 166 <ul>
 167 <li><code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code></li>
 168 <li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
 169 </ul>
 170 </div>
 171 </div>
 172 <div class="bottomlang">
 173 <p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
 174 <a href="../en/mod/prefork.html" title="English">&nbsp;en&nbsp;</a> |
 175 <a href="../es/mod/prefork.html" hreflang="es" rel="alternate" title="Español">&nbsp;es&nbsp;</a> |
 176 <a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
 177 <a href="../tr/mod/prefork.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
 178 </div><div id="footer">
 179 <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>
 180 <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>
 181 </body></html>