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>worker - 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.min.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 2.4</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 2.4</a> > <a href="./">Modules</a></div> 24<div id="page-content"> 25<div id="preamble"><h1>Apache MPM worker</h1> 26<div class="toplang"> 27<p><span>Available Languages: </span><a href="/de/mod/worker.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | 28<a href="/en/mod/worker.html" title="English"> en </a> | 29<a href="/fr/mod/worker.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a> | 30<a href="/ja/mod/worker.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 31<a href="/tr/mod/worker.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 32</div> 33<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Multi-Processing Module implementing a hybrid 34 multi-threaded multi-process web server</td></tr> 35<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr> 36<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>mpm_worker_module</td></tr> 37<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>worker.c</td></tr></table> 38<h3>Summary</h3> 39 40 <p>This Multi-Processing Module (MPM) implements a hybrid 41 multi-process multi-threaded server. By using threads to serve 42 requests, it is able to serve a large number of requests with 43 fewer system resources than a process-based server. However, it 44 retains much of the stability of a process-based server by 45 keeping multiple processes available, each with many threads.</p> 46 47 <p>The most important directives used to control this MPM are 48 <code class="directive"><a href="/mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code>, which 49 controls the number of threads deployed by each child process and 50 <code class="directive"><a href="/mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code>, which 51 controls the maximum total number of threads that may be 52 launched.</p> 53</div> 54<div id="quickview"><h3 class="directives">Directives</h3> 55<ul id="toc"> 56<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li> 57<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li> 58<li><img alt="" src="/images/right.gif" /> <a href="mod_unixd.html#group">Group</a></li> 59<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li> 60<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li> 61<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxconnectionsperchild">MaxConnectionsPerChild</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#maxrequestworkers">MaxRequestWorkers</a></li> 64<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#maxsparethreads">MaxSpareThreads</a></li> 65<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#minsparethreads">MinSpareThreads</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#threadlimit">ThreadLimit</a></li> 73<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#threadsperchild">ThreadsPerChild</a></li> 74<li><img alt="" src="/images/right.gif" /> <a href="mpm_common.html#threadstacksize">ThreadStackSize</a></li> 75<li><img alt="" src="/images/right.gif" /> <a href="mod_unixd.html#user">User</a></li> 76</ul> 77<h3>Topics</h3> 78<ul id="topics"> 79<li><img alt="" src="/images/down.gif" /> <a href="#how-it-works">How it Works</a></li> 80</ul><h3>See also</h3> 81<ul class="seealso"> 82<li><a href="/bind.html">Setting which addresses and ports Apache HTTP Server uses</a></li> 83</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 84<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 85<div class="section"> 86<h2><a name="how-it-works" id="how-it-works">How it Works</a></h2> 87 <p>A single control process (the parent) is responsible for launching 88 child processes. Each child process creates a fixed number of server 89 threads as specified in the <code class="directive"><a href="/mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> directive, as well 90 as a listener thread which listens for connections and passes them 91 to a server thread for processing when they arrive.</p> 92 93 <p>Apache HTTP Server always tries to maintain a pool of <dfn>spare</dfn> or 94 idle server threads, which stand ready to serve incoming 95 requests. In this way, clients do not need to wait for a new 96 threads or processes to be created before their requests can be 97 served. The number of processes that will initially launch is 98 set by the <code class="directive"><a href="/mod/mpm_common.html#startservers">StartServers</a></code> 99 directive. During operation, the server assesses the total number 100 of idle threads in all processes, and forks or kills processes to 101 keep this number within the boundaries specified by <code class="directive"><a href="/mod/mpm_common.html#minsparethreads">MinSpareThreads</a></code> and <code class="directive"><a href="/mod/mpm_common.html#maxsparethreads">MaxSpareThreads</a></code>. Since this 102 process is very self-regulating, it is rarely necessary to modify 103 these directives from their default values. The maximum number of 104 clients that may be served simultaneously (i.e., the maximum total 105 number of threads in all processes) is determined by the 106 <code class="directive"><a href="/mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> directive. 107 The maximum number of active child processes is determined by 108 the <code class="directive"><a href="/mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> 109 directive divided by the <code class="directive"><a href="/mod/mpm_common.html#threadsperchild"> 110 ThreadsPerChild</a></code> directive.</p> 111 112 <p>Two directives set hard limits on the number of active child 113 processes and the number of server threads in a child process, 114 and can only be changed by fully stopping the server and then 115 starting it again. <code class="directive"><a href="/mod/mpm_common.html#serverlimit">ServerLimit 116 </a></code> is a hard limit on the number of active child 117 processes, and must be greater than or equal to the 118 <code class="directive"><a href="/mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> 119 directive divided by the <code class="directive"><a href="/mod/mpm_common.html#threadsperchild"> 120 ThreadsPerChild</a></code> directive. 121 <code class="directive"><a href="/mod/mpm_common.html#threadlimit">ThreadLimit</a></code> is a hard 122 limit of the number of server threads, and must be greater than 123 or equal to the <code class="directive"><a href="/mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> directive.</p> 124 125 <p>In addition to the set of active child processes, there may 126 be additional child processes which are terminating, but where at 127 least one server thread is still handling an existing client 128 connection. Up to <code class="directive"><a href="/mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> terminating processes 129 may be present, though the actual number can be expected to be 130 much smaller. This behavior can be avoided by disabling the 131 termination of individual child processes, which is achieved using 132 the following:</p> 133 134 <ul> 135 <li>set the value of <code class="directive"><a href="/mod/mpm_common.html#maxconnectionsperchild"> 136 MaxConnectionsPerChild</a></code> to zero</li> 137 138 <li>set the value of <code class="directive"><a href="/mod/mpm_common.html#maxsparethreads"> 139 MaxSpareThreads</a></code> to the same value as 140 <code class="directive"><a href="/mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code></li> 141 </ul> 142 143 <p>A typical configuration of the process-thread controls in 144 the <code class="module"><a href="/mod/worker.html">worker</a></code> MPM could look as follows:</p> 145 146 <pre class="prettyprint lang-config">ServerLimit 16 147StartServers 2 148MaxRequestWorkers 150 149MinSpareThreads 25 150MaxSpareThreads 75 151ThreadsPerChild 25</pre> 152 153 154 <p>While the parent process is usually started as <code>root</code> 155 under Unix in order to bind to port 80, the child processes and threads 156 are launched by the server 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 157 the privileges of the Apache HTTP Server child processes. The child processes 158 must be able to read all the content that will be served, but 159 should have as few privileges beyond that as possible. In 160 addition, unless <code class="program"><a href="/programs/suexec.html">suexec</a></code> is used, 161 these directives also set the privileges which will be inherited 162 by CGI scripts.</p> 163 164 <p><code class="directive"><a href="/mod/mpm_common.html#maxconnectionsperchild">MaxConnectionsPerChild</a></code> 165 controls how frequently the server recycles processes by killing 166 old ones and launching new ones.</p> 167 168 <p>This MPM uses the <code>mpm-accept</code> mutex to serialize 169 access to incoming connections when subject to the thundering herd 170 problem (generally, when there are multiple listening sockets). 171 The implementation aspects of this mutex can be configured with the 172 <code class="directive"><a href="/mod/core.html#mutex">Mutex</a></code> directive. The <a href="/misc/perf-tuning.html">performance hints</a> 173 documentation has additional information about this mutex.</p> 174</div> 175</div> 176<div class="bottomlang"> 177<p><span>Available Languages: </span><a href="/de/mod/worker.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | 178<a href="/en/mod/worker.html" title="English"> en </a> | 179<a href="/fr/mod/worker.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a> | 180<a href="/ja/mod/worker.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 181<a href="/tr/mod/worker.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 182</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. 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