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Extensible Markup Language  |  2004-05-18  |  13KB  |  178 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" />
  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="<-" 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-project/">Documentation</a> > <a href="../">Version 2.0</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="../es/mod/prefork.html" hreflang="es" rel="alternate" title="Espa±ol"> es </a> |
  27. <a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
  28. </div>
  29. <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>
  30. <tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  31. <tr><th><a href="module-dict.html#ModuleIdentifier">ModuleáIdentifier:</a></th><td>mpm_prefork_module</td></tr>
  32. <tr><th><a href="module-dict.html#SourceFile">SourceáFile:</a></th><td>prefork.c</td></tr></table>
  33. <h3>Summary</h3>
  34.  
  35.     <p>This Multi-Processing Module (MPM) implements a non-threaded,
  36.     pre-forking web server that handles requests in a manner similar
  37.     to Apache 1.3.  It is appropriate for sites that need to avoid
  38.     threading for compatibility with non-thread-safe libraries.  It
  39.     is also the best MPM for isolating each request, so that a problem
  40.     with a single request will not affect any other.</p>
  41.  
  42.     <p>This MPM is very self-regulating, so it is rarely necessary to
  43.     adjust its configuration directives.  Most important is that
  44.     <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> be big enough to 
  45.     handle as many simultaneous requests as you expect to receive, but
  46.     small enough to assure that there is enough physical RAM for all
  47.     processes.</p>
  48. </div>
  49. <div id="quickview"><h3 class="directives">Directives</h3>
  50. <ul id="toc">
  51. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#acceptmutex">AcceptMutex</a></li>
  52. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#bs2000account">BS2000Account</a></li>
  53. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
  54. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li>
  55. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#group">Group</a></li>
  56. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li>
  57. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
  58. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#lockfile">LockFile</a></li>
  59. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li>
  60. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li>
  61. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>
  62. <li><img alt="" src="../images/down.gif" /> <a href="#maxspareservers">MaxSpareServers</a></li>
  63. <li><img alt="" src="../images/down.gif" /> <a href="#minspareservers">MinSpareServers</a></li>
  64. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li>
  65. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
  66. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
  67. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li>
  68. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li>
  69. <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#user">User</a></li>
  70. </ul>
  71. <h3>Topics</h3>
  72. <ul id="topics">
  73. <li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it Works</a></li>
  74. </ul><h3>See also</h3>
  75. <ul class="seealso">
  76. <li><a href="../bind.html">Setting which addresses and ports Apache
  77. uses</a></li>
  78. </ul></div>
  79. <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  80. <div class="section">
  81. <h2><a name="how-it-works" id="how-it-works">How it Works</a></h2>
  82.     <p>A single control process is responsible for launching child
  83.     processes which listen for connections and serve them when they
  84.     arrive. Apache always tries to maintain several <dfn>spare</dfn>
  85.     or idle server processes, which stand ready to serve incoming
  86.     requests. In this way, clients do not need to wait for a new
  87.     child processes to be forked before their requests can be
  88.     served.</p>
  89.  
  90.     <p>The <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>,
  91.     <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>,
  92.     <code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code>, and
  93.     <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> regulate how
  94.     the parent process creates children to serve requests. In general,
  95.     Apache is very self-regulating, so most sites do not need to
  96.     adjust these directives from their default values. Sites which
  97.     need to serve more than 256 simultaneous requests may need to
  98.     increase <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>,
  99.     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
  100.     thrashing (swapping memory to disk and back). More information
  101.     about tuning process creation is provided in the <a href="../misc/perf-tuning.html">performance hints</a>
  102.     documentation.</p>
  103.  
  104.     <p>While the parent process is usually started as <code>root</code>
  105.     under Unix in order to bind to port 80, the child processes are
  106.     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
  107.     the privileges of the Apache child processes. The child processes
  108.     must be able to read all the content that will be served, but
  109.     should have as few privileges beyond that as possible.</p>
  110.  
  111.     <p><code class="directive"><a href="../mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code>
  112.     controls how frequently the server recycles processes by killing
  113.     old ones and launching new ones.</p>
  114. </div>
  115. <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  116. <div class="directive-section"><h2><a name="MaxSpareServers" id="MaxSpareServers">MaxSpareServers</a> <a name="maxspareservers" id="maxspareservers">Directive</a></h2>
  117. <table class="directive">
  118. <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle child server processes</td></tr>
  119. <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareServers <var>number</var></code></td></tr>
  120. <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxSpareServers 10</code></td></tr>
  121. <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  122. <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  123. <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
  124. </table>
  125.     <p>The <code class="directive">MaxSpareServers</code> directive sets the
  126.     desired maximum number of <em>idle</em> child server processes. An
  127.     idle process is one which is not handling a request. If there are
  128.     more than <code class="directive">MaxSpareServers</code> idle, then the
  129.     parent process will kill off the excess processes.</p>
  130.  
  131.     <p>Tuning of this parameter should only be necessary on very
  132.     busy sites. Setting this parameter to a large number is almost
  133.     always a bad idea. If you are trying to set the value lower than
  134.     <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, Apache
  135.     will automatically adjust it to <code class="directive">MinSpareServers</code><code> + 1</code>.</p>
  136.  
  137. <h3>See also</h3>
  138. <ul>
  139. <li><code class="directive"><a href="#minspareservers">MinSpareServers</a></code></li>
  140. <li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
  141. </ul>
  142. </div>
  143. <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  144. <div class="directive-section"><h2><a name="MinSpareServers" id="MinSpareServers">MinSpareServers</a> <a name="minspareservers" id="minspareservers">Directive</a></h2>
  145. <table class="directive">
  146. <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle child server processes</td></tr>
  147. <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareServers <var>number</var></code></td></tr>
  148. <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MinSpareServers 5</code></td></tr>
  149. <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  150. <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  151. <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
  152. </table>
  153.     <p>The <code class="directive">MinSpareServers</code> directive sets the
  154.     desired minimum number of <em>idle</em> child server processes. An
  155.     idle process is one which is not handling a request. If there are
  156.     fewer than <code class="directive">MinSpareServers</code> idle, then the parent
  157.     process creates new children at a maximum rate of 1 per second.</p>
  158.  
  159.     <p>Tuning of this parameter should only be necessary on very
  160.     busy sites. Setting this parameter to a large number is almost
  161.     always a bad idea.</p>
  162.  
  163. <h3>See also</h3>
  164. <ul>
  165. <li><code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code></li>
  166. <li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
  167. </ul>
  168. </div>
  169. </div>
  170. <div class="bottomlang">
  171. <p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
  172. <a href="../en/mod/prefork.html" title="English"> en </a> |
  173. <a href="../es/mod/prefork.html" hreflang="es" rel="alternate" title="Espa±ol"> es </a> |
  174. <a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
  175. </div><div id="footer">
  176. <p class="apache">Copyright 1999-2004 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>
  177. <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>
  178. </body></html>