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-<title>worker - Apache HTTP Server</title>
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-<p class="apache">Apache HTTP Server Version 2.0</p>
-<img alt="" src="../images/feather.gif" /></div>
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-<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 2.0</a> > <a href="./">Modules</a></div>
-<div id="page-content">
-<div id="preamble"><h1>Apache MPM worker</h1>
-<div class="toplang">
-<p><span>Available Languages: </span><a href="../de/mod/worker.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
-<a href="../en/mod/worker.html" title="English"> en </a> |
-<a href="../es/mod/worker.html" hreflang="es" rel="alternate" title="Español"> es </a> |
-<a href="../ja/mod/worker.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
-<a href="../tr/mod/worker.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
-</div>
-<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Multi-Processing Module implementing a hybrid
- multi-threaded multi-process web server</td></tr>
-<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr>
-<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>mpm_worker_module</td></tr>
-<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>worker.c</td></tr></table>
-<h3>Summary</h3>
-
- <p>This Multi-Processing Module (MPM) implements a hybrid
- multi-process multi-threaded server. By using threads to serve
- requests, it is able to serve a large number of requests with
- less system resources than a process-based server. Yet it
- retains much of the stability of a process-based server by
- keeping multiple processes available, each with many threads.</p>
-
- <p>The most important directives used to control this MPM are
- <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code>, which
- controls the number of threads deployed by each child process and
- <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>, which
- controls the maximum total number of threads that may be
- launched.</p>
-</div>
-<div id="quickview"><h3 class="directives">Directives</h3>
-<ul id="toc">
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#acceptmutex">AcceptMutex</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#group">Group</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#lockfile">LockFile</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxsparethreads">MaxSpareThreads</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#minsparethreads">MinSpareThreads</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#receivebuffersize">ReceiveBufferSize</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#threadlimit">ThreadLimit</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#threadsperchild">ThreadsPerChild</a></li>
-<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#user">User</a></li>
-</ul>
-<h3>Topics</h3>
-<ul id="topics">
-<li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it Works</a></li>
-</ul><h3>See also</h3>
-<ul class="seealso">
-<li><a href="../bind.html">Setting which addresses and ports Apache
-uses</a></li>
-</ul></div>
-<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
-<div class="section">
-<h2><a name="how-it-works" id="how-it-works">How it Works</a></h2>
- <p>A single control process (the parent) is responsible for launching
- child processes. Each child process creates a fixed number of server
- threads as specified in the <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> directive, as well
- as a listener thread which listens for connections and passes them
- to a server thread for processing when they arrive.</p>
-
- <p>Apache always tries to maintain a pool of <dfn>spare</dfn> or
- idle server threads, which stand ready to serve incoming
- requests. In this way, clients do not need to wait for a new
- threads or processes to be created before their requests can be
- served. The number of processes that will initially launched is
- set by the <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>
- directive. Then during operation, Apache assesses the total number
- of idle threads in all processes, and forks or kills processes to
- 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
- process is very self-regulating, it is rarely necessary to modify
- these directives from their default values. The maximum number of
- clients that may be served simultaneously (i.e., the maximum total
- number of threads in all processes) is determined by the
- <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> directive.
- The maximum number of active child processes is determined by
- the <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>
- directive divided by the <code class="directive"><a href="../mod/mpm_common.html# threadsperchild">
- ThreadsPerChild</a></code> directive.</p>
-
- <p>Two directives set hard limits on the number of active child
- processes and the number of server threads in a child process,
- and can only be changed by fully stopping the server and then
- starting it again. <code class="directive"><a href="../mod/mpm_common.html#serverlimit ">ServerLimit
- </a></code> is a hard limit on the number of active child
- processes, and must be greater than or equal to the
- <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>
- directive divided by the <code class="directive"><a href="../mod/mpm_common.html# threadsperchild">
- ThreadsPerChild</a></code> directive.
- <code class="directive"><a href="../mod/mpm_common.html#threadlimit">ThreadLimit</a></code> is a hard
- limit of the number of server threads, and must be greater than
- or equal to the <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> directive. If
- non-default values are specified for these directives, they
- should appear before other <code class="module"><a href="../mod/worker.html">worker</a></code> directives.</p>
-
- <p>In addition to the set of active child processes, there may
- be additional child processes which are terminating but where at
- least one server thread is still handling an existing client
- connection. Up to <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> terminating processes
- may be present, though the actual number can be expected to be
- much smaller. This behavior can be avoided by disabling the
- termination of individual child processes, which is achieved by
- the following:</p>
-
- <ul>
- <li>set the value of <code class="directive"><a href="../mod/mpm_common.html# maxrequestsperchild">
- MaxRequestsPerChild</a></code> to zero</li>
-
- <li>set the value of <code class="directive"><a href="../mod/mpm_common.html# maxsparethreads">
- MaxSpareThreads</a></code> to the same value as
- <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code></li>
- </ul>
-
- <p>A typical configuration of the process-thread controls in
- the <code class="module"><a href="../mod/worker.html">worker</a></code> MPM could look as follows:</p>
-
- <div class="example"><p><code>
- ServerLimit 16<br />
- StartServers 2<br />
- MaxClients 150<br />
- MinSpareThreads 25<br />
- MaxSpareThreads 75<br />
- ThreadsPerChild 25
- </code></p></div>
-
- <p>While the parent process is usually started as <code>root</code>
- under Unix in order to bind to port 80, the child processes and threads
- are 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
- the privileges of the Apache child processes. The child processes
- must be able to read all the content that will be served, but
- should have as few privileges beyond that as possible. In
- addition, unless <code class="program"><a href="../programs/suexec.html">suexec</a></code> is used,
- these directives also set the privileges which will be inherited
- by CGI scripts.</p>
-
- <p><code class="directive"><a href="../mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code>
- controls how frequently the server recycles processes by killing
- old ones and launching new ones.</p>
-</div>
-</div>
-<div class="bottomlang">
-<p><span>Available Languages: </span><a href="../de/mod/worker.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
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-<a href="../ja/mod/worker.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
-<a href="../tr/mod/worker.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
-</div><div id="footer">
-<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>
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