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Extensible Markup Language  |  2007-09-01  |  13KB  |  176 lines
  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">
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  8. <title>prefork - Apache HTTP Server</title>
  9. <link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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  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 2.2</p>
  17. <img alt="" src="../images/feather.gif" /></div>
  18. <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
  19. <div id="path">
  20. <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>
  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"> de </a> |
  25. <a href="../en/mod/prefork.html" title="English"> en </a> |
  26. <a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
  27. </div>
  28. <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>
  29. <tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  30. <tr><th><a href="module-dict.html#ModuleIdentifier">ModuleáIdentifier:</a></th><td>mpm_prefork_module</td></tr>
  31. <tr><th><a href="module-dict.html#SourceFile">SourceáFile:</a></th><td>prefork.c</td></tr></table>
  32. <h3>Summary</h3>
  33.  
  34.     <p>This Multi-Processing Module (MPM) implements a non-threaded,
  35.     pre-forking web server that handles requests in a manner similar
  36.     to Apache 1.3.  It is appropriate for sites that need to avoid
  37.     threading for compatibility with non-thread-safe libraries.  It
  38.     is also the best MPM for isolating each request, so that a problem
  39.     with a single request will not affect any other.</p>
  40.  
  41.     <p>This MPM is very self-regulating, so it is rarely necessary to
  42.     adjust its configuration directives.  Most important is that
  43.     <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> be big enough to 
  44.     handle as many simultaneous requests as you expect to receive, but
  45.     small enough to assure that there is enough physical RAM for all
  46.     processes.</p>
  47. </div>
  48. <div id="quickview"><h3 class="directives">Directives</h3>
  49. <ul id="toc">
  50. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#acceptmutex">AcceptMutex</a></li>
  51. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
  52. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li>
  53. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#group">Group</a></li>
  54. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li>
  55. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
  56. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#lockfile">LockFile</a></li>
  57. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li>
  58. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li>
  59. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>
  60. <li><img alt="" src="../images/down.gif" /> <a href="#maxspareservers">MaxSpareServers</a></li>
  61. <li><img alt="" src="../images/down.gif" /> <a href="#minspareservers">MinSpareServers</a></li>
  62. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li>
  63. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#receivebuffersize">ReceiveBufferSize</a></li>
  64. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
  65. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
  66. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li>
  67. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li>
  68. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#user">User</a></li>
  69. </ul>
  70. <h3>Topics</h3>
  71. <ul id="topics">
  72. <li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it Works</a></li>
  73. </ul><h3>See also</h3>
  74. <ul class="seealso">
  75. <li><a href="../bind.html">Setting which addresses and ports Apache
  76. uses</a></li>
  77. </ul></div>
  78. <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  79. <div class="section">
  80. <h2><a name="how-it-works" id="how-it-works">How it Works</a></h2>
  81.     <p>A single control process is responsible for launching child
  82.     processes which listen for connections and serve them when they
  83.     arrive. Apache always tries to maintain several <dfn>spare</dfn>
  84.     or idle server processes, which stand ready to serve incoming
  85.     requests. In this way, clients do not need to wait for a new
  86.     child processes to be forked before their requests can be
  87.     served.</p>
  88.  
  89.     <p>The <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>,
  90.     <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>,
  91.     <code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code>, and
  92.     <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> regulate how
  93.     the parent process creates children to serve requests. In general,
  94.     Apache is very self-regulating, so most sites do not need to
  95.     adjust these directives from their default values. Sites which
  96.     need to serve more than 256 simultaneous requests may need to
  97.     increase <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>,
  98.     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
  99.     thrashing (swapping memory to disk and back). More information
  100.     about tuning process creation is provided in the <a href="../misc/perf-tuning.html">performance hints</a>
  101.     documentation.</p>
  102.  
  103.     <p>While the parent process is usually started as <code>root</code>
  104.     under Unix in order to bind to port 80, the child processes are
  105.     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
  106.     the privileges of the Apache child processes. The child processes
  107.     must be able to read all the content that will be served, but
  108.     should have as few privileges beyond that as possible.</p>
  109.  
  110.     <p><code class="directive"><a href="../mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code>
  111.     controls how frequently the server recycles processes by killing
  112.     old ones and launching new ones.</p>
  113. </div>
  114. <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  115. <div class="directive-section"><h2><a name="MaxSpareServers" id="MaxSpareServers">MaxSpareServers</a> <a name="maxspareservers" id="maxspareservers">Directive</a></h2>
  116. <table class="directive">
  117. <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle child server processes</td></tr>
  118. <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareServers <var>number</var></code></td></tr>
  119. <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxSpareServers 10</code></td></tr>
  120. <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  121. <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  122. <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
  123. </table>
  124.     <p>The <code class="directive">MaxSpareServers</code> directive sets the
  125.     desired maximum number of <em>idle</em> child server processes. An
  126.     idle process is one which is not handling a request. If there are
  127.     more than <code class="directive">MaxSpareServers</code> idle, then the
  128.     parent process will kill off the excess processes.</p>
  129.  
  130.     <p>Tuning of this parameter should only be necessary on very
  131.     busy sites. Setting this parameter to a large number is almost
  132.     always a bad idea. If you are trying to set the value equal to or lower than
  133.     <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, Apache
  134.     will automatically adjust it to <code class="directive">MinSpareServers</code><code> + 1</code>.</p>
  135.  
  136. <h3>See also</h3>
  137. <ul>
  138. <li><code class="directive"><a href="#minspareservers">MinSpareServers</a></code></li>
  139. <li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
  140. </ul>
  141. </div>
  142. <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  143. <div class="directive-section"><h2><a name="MinSpareServers" id="MinSpareServers">MinSpareServers</a> <a name="minspareservers" id="minspareservers">Directive</a></h2>
  144. <table class="directive">
  145. <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle child server processes</td></tr>
  146. <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareServers <var>number</var></code></td></tr>
  147. <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MinSpareServers 5</code></td></tr>
  148. <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  149. <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  150. <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
  151. </table>
  152.     <p>The <code class="directive">MinSpareServers</code> directive sets the
  153.     desired minimum number of <em>idle</em> child server processes. An
  154.     idle process is one which is not handling a request. If there are
  155.     fewer than <code class="directive">MinSpareServers</code> idle, then the parent
  156.     process creates new children at a maximum rate of 1 per second.</p>
  157.  
  158.     <p>Tuning of this parameter should only be necessary on very
  159.     busy sites. Setting this parameter to a large number is almost
  160.     always a bad idea.</p>
  161.  
  162. <h3>See also</h3>
  163. <ul>
  164. <li><code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code></li>
  165. <li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
  166. </ul>
  167. </div>
  168. </div>
  169. <div class="bottomlang">
  170. <p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
  171. <a href="../en/mod/prefork.html" title="English"> en </a> |
  172. <a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
  173. </div><div id="footer">
  174. <p class="apache">Copyright 2007 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>
  175. <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>
  176. </body></html>