<?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type" /> <!-- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX This file is generated from xml source: DO NOT EDIT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX --> <title>worker - Apache HTTP Server Version 2.4</title> <link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> <link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> <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" /> <script src="../style/scripts/prettify.min.js" type="text/javascript"> </script> <link href="../images/favicon.ico" rel="shortcut icon" /></head> <body> <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.png" /></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 requests, it is able to serve a large number of requests with 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 <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"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><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 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>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mpm_worker">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mpm_worker">Report a bug</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> <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. 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 (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 <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#maxconnectionsperchild">MaxConnectionsPerChild</a></code> controls how frequently the server recycles processes by killing old ones and launching new ones.</p> <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> <script type="text/javascript"><!--//--><![CDATA[//><!-- var comments_shortname = 'httpd'; var comments_identifier = 'http://httpd.apache.org/docs/2.4/mod/worker.html'; (function(w, d) { if (w.location.hostname.toLowerCase() == "httpd.apache.org") { d.write('<div id="comments_thread"><\/div>'); var s = d.createElement('script'); s.type = 'text/javascript'; s.async = true; s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier; (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s); } else { d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>'); } })(window, document); //--><!]]></script></div><div id="footer"> <p class="apache">Copyright 2018 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> <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></div><script type="text/javascript"><!--//--><![CDATA[//><!-- if (typeof(prettyPrint) !== 'undefined') { prettyPrint(); } //--><!]]></script> </body></html>