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- --><title>worker- Apache HTTP Server</title><link href="../style/manual.css" type="text/css" rel="stylesheet"/></head><body><blockquote><div align="center"><img src="../images/sub.gif" alt="[APACHE DOCUMENTATION]"/><h3>Apache HTTP Server Version 2.0</h3></div><h1 align="center">Apache Module worker</h1><table cellspacing="1" cellpadding="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td valign="top"><span class="help">Description:</span></td><td>Multi-Processing Module implementing a hybrid
- multi-threaded multi-process web server</td></tr><tr><td><a href="module-dict.html#Status" class="help">Status:</a></td><td>MPM</td></tr><tr><td><a href="module-dict.html#ModuleIdentifier" class="help">Module Identifier:</a></td><td>mpm_worker_module</td></tr></table></td></tr></table><h2>Summary</h2>
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+<div id="page-header">
+<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>
+<p class="apache">Apache HTTP Server Version 2.4</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
+<div id="path">
+<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>
+<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="../fr/mod/worker.html" hreflang="fr" rel="alternate" title="Français"> fr </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
+ 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
+ fewer system resources than a process-based server. However, 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
- <a href="mpm_common.html#threadsperchild" class="directive"><code class="directive">ThreadsPerChild</code></a> and
- <a href="mpm_common.html#maxclients" class="directive"><code class="directive">MaxClients</code></a>. By multiplying
- together the value of these directives you define the total number
- of simultaneous connections that the server can handle.</p>
-
-<h2>Directives</h2><ul><li><a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li><li><a href="mpm_common.html#group">Group</a></li><li><a href="mpm_common.html#listen">Listen</a></li><li><a href="mpm_common.html#listenbacklog">ListenBacklog</a></li><li><a href="mpm_common.html#lockfile">LockFile</a></li><li><a href="mpm_common.html#maxclients">MaxClients</a></li><li><a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li><li><a href="mpm_common.html#maxsparethreads">MaxSpareThreads</a></li><li><a href="mpm_common.html#minsparethreads">MinSpareThreads</a></li><li><a href="mpm_common.html#pidfile">PidFile</a></li><li><a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li><li><a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li><li><a href="mpm_common.html#serverlimit">ServerLimit</a></li><li><a href="mpm_common.html#startservers">StartServers</a></li><li><a href="mpm_common.html#threadlimit">ThreadLimit</a></li><li><a href="mpm_common.html#threadsperchild">ThreadsPerChild</a></li><li><a href="mpm_common.html#user">User</a></li></ul><p><strong>See also </strong></p><ul><li><a href="../bind.html">Setting which addresses and
- ports Apache uses</a></li></ul><h2>How it Works</h2>
- <p>Each process has a fixed
- number of threads. The server adjusts to handle load by
- increasing or decreasing the number of processes.</p>
-
- <p>A single control process is responsible for launching child
- processes. Each child process creates a fixed number of threads as
- specified in the <a href="mpm_common.html#threadsperchild" class="directive"><code class="directive">ThreadsPerChild</code></a> directive. The
- individual threads then listen for connections and serve them when
- they arrive.</p>
-
- <p>Apache always tries to maintain a pool of <em>spare</em> or
+ <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#maxrequestworkers">MaxRequestWorkers</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#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="mod_unixd.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#maxconnectionsperchild">MaxConnectionsPerChild</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#maxrequestworkers">MaxRequestWorkers</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#threadstacksize">ThreadStackSize</a></li>
+<li><img alt="" src="../images/right.gif" /> <a href="mod_unixd.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 HTTP Server uses</a></li>
+</ul><ul class="seealso"><li><a href="#comments_section">Comments</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 HTTP Server 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. 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 <a href="mpm_common.html#minsparethreads" class="directive"><code class="directive">MinSpareThreads</code></a> and <a href="mpm_common.html#maxsparethreads" class="directive"><code class="directive">MaxSpareThreads</code></a>. Since this
+ served. The number of processes that will initially launch is
+ set by the <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>
+ directive. During operation, the server 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 is determined by
- multiplying the maximum number of server processes that will be
- created (<a href="mpm_common.html#maxclients" class="directive"><code class="directive">MaxClients</code></a>) by
- the number of threads created in each process (<a href="mpm_common.html#threadsperchild" class="directive"><code class="directive">ThreadsPerChild</code></a>).</p>
-
- <p>While the parent process is usually started as root under Unix
- in order to bind to port 80, the child processes and threads are
- launched by Apache as a less-privileged user. The <a href="mpm_common.html#user" class="directive"><code class="directive">User</code></a> and <a href="mpm_common.html#group" class="directive"><code class="directive">Group</code></a> directives are used to set
- the privileges of the Apache child processes. The child processes
+ 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#maxrequestworkers">MaxRequestWorkers</a></code> directive.
+ The maximum number of active child processes is determined by
+ the <code class="directive"><a href="../mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</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#maxrequestworkers">MaxRequestWorkers</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.</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#maxrequestworkers">MaxRequestWorkers</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 using
+ the following:</p>
+
+ <ul>
+ <li>set the value of <code class="directive"><a href="../mod/mpm_common.html#maxconnectionsperchild">
+ MaxConnectionsPerChild</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#maxrequestworkers">MaxRequestWorkers</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>
+
+ <pre class="prettyprint lang-config">
+ServerLimit 16
+StartServers 2
+MaxRequestWorkers 150
+MinSpareThreads 25
+MaxSpareThreads 75
+ThreadsPerChild 25
+ </pre>
+
+
+ <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 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
+ the privileges of the Apache HTTP Server 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 <a href="../suexec.html">suexec</a> is used,
+ 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><a href="mpm_common.html#maxrequestsperchild" class="directive"><code class="directive">MaxRequestsPerChild</code></a>
+ <p><code class="directive"><a href="../mod/mpm_common.html#maxconnectionsperchild">MaxConnectionsPerChild</a></code>
controls how frequently the server recycles processes by killing
old ones and launching new ones.</p>
-<hr/></blockquote><h3 align="center">Apache HTTP Server Version 2.0</h3><a href="./"><img src="../images/index.gif" alt="Index"/></a><a href="../"><img src="../images/home.gif" alt="Home"/></a></body></html>
\ No newline at end of file
+
+ <p>This MPM uses the <code>mpm-accept</code> mutex to serialize
+ access to incoming connections when subject to the thundering herd
+ problem (generally, when there are multiple listening sockets).
+ The implementation aspects of this mutex can be configured with the
+ <code class="directive"><a href="../mod/core.html#mutex">Mutex</a></code> directive. The <a href="../misc/perf-tuning.html">performance hints</a>
+ documentation has additional information about this mutex.</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> |
+<a href="../en/mod/worker.html" title="English"> en </a> |
+<a href="../fr/mod/worker.html" hreflang="fr" rel="alternate" title="Français"> fr </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><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. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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projects / apache / blobdiff