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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-08 19:09:22 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-08 19:09:22 +0000
commit2faa747e2303ee774a4b4aace961188e950e185a (patch)
tree604e79c7481956ce48f458e3546eaf1090b3ffff /docs/manual/mod/prefork.html.en
parentInitial commit. (diff)
downloadapache2-2faa747e2303ee774a4b4aace961188e950e185a.tar.xz
apache2-2faa747e2303ee774a4b4aace961188e950e185a.zip
Adding upstream version 2.4.58.upstream/2.4.58
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<?xml version="1.0" encoding="UTF-8"?>
+<!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=UTF-8" http-equiv="Content-Type" />
+<!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>prefork - 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="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.4</a> &gt; <a href="./">Modules</a></div>
+<div id="page-content">
+<div id="preamble"><h1>Apache MPM prefork</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
+<a href="../en/mod/prefork.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../fr/mod/prefork.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
+<a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../tr/mod/prefork.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
+</div>
+<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>
+<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_prefork_module</td></tr>
+<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>prefork.c</td></tr></table>
+<h3>Summary</h3>
+
+ <p>This Multi-Processing Module (MPM) implements a non-threaded,
+ pre-forking web server. Each server process may answer incoming
+ requests, and a parent process manages the size of the server pool.
+ It is appropriate for sites that need to avoid
+ threading for compatibility with non-thread-safe libraries. It
+ is also the best MPM for isolating each request, so that a problem
+ with a single request will not affect any other.</p>
+
+ <p>This MPM is very self-regulating, so it is rarely necessary to
+ adjust its configuration directives. Most important is that
+ <code class="directive"><a href="../mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> be big enough
+ to handle as many simultaneous requests as you expect to receive, but
+ small enough to assure that there is enough physical RAM for all
+ processes.</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/down.gif" /> <a href="#maxspareservers">MaxSpareServers</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#minspareservers">MinSpareServers</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="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__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mpm_prefork">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mpm_prefork">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 is responsible for launching child
+ processes which listen for connections and serve them when they
+ arrive. Apache httpd always tries to maintain several <dfn>spare</dfn>
+ or idle server processes, which stand ready to serve incoming
+ requests. In this way, clients do not need to wait for a new
+ child processes to be forked before their requests can be
+ served.</p>
+
+ <p>The <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>,
+ <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>,
+ <code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code>, and
+ <code class="directive"><a href="../mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> regulate how
+ the parent process creates children to serve requests. In general,
+ Apache httpd is very self-regulating, so most sites do not need to
+ adjust these directives from their default values. Sites which
+ need to serve more than 256 simultaneous requests may need to
+ increase <code class="directive"><a href="../mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code>,
+ while sites with limited memory may need to decrease <code class="directive"><a href="../mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> to keep the server from
+ thrashing (swapping memory to disk and back). More information
+ about tuning process creation is provided in the <a href="../misc/perf-tuning.html">performance hints</a>
+ documentation.</p>
+
+ <p>While the parent process is usually started as <code>root</code>
+ under Unix in order to bind to port 80, the child processes are
+ launched by Apache httpd 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 httpd 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.</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 class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MaxSpareServers" id="MaxSpareServers">MaxSpareServers</a> <a name="maxspareservers" id="maxspareservers">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle child server processes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareServers <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxSpareServers 10</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
+</table>
+ <p>The <code class="directive">MaxSpareServers</code> directive sets the
+ desired maximum number of <em>idle</em> child server processes. An
+ idle process is one which is not handling a request. If there are
+ more than <code class="directive">MaxSpareServers</code> idle, then the
+ parent process will kill off the excess processes.</p>
+
+ <p>Tuning of this parameter should only be necessary on very
+ busy sites. Setting this parameter to a large number is almost
+ always a bad idea. If you are trying to set the value equal to or lower than
+ <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, Apache HTTP Server
+ will automatically adjust it to <code class="directive">MinSpareServers</code><code> + 1</code>.</p>
+
+<h3>See also</h3>
+<ul>
+<li><code class="directive"><a href="#minspareservers">MinSpareServers</a></code></li>
+<li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
+<li><code class="directive"><a href="../mod/mpm_common.html#maxsparethreads">MaxSpareThreads</a></code></li>
+</ul>
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MinSpareServers" id="MinSpareServers">MinSpareServers</a> <a name="minspareservers" id="minspareservers">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle child server processes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareServers <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MinSpareServers 5</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr>
+</table>
+ <p>The <code class="directive">MinSpareServers</code> directive sets the
+ desired minimum number of <em>idle</em> child server processes. An
+ idle process is one which is not handling a request. If there are
+ fewer than <code class="directive">MinSpareServers</code> idle, then the parent
+ process creates new children: It will spawn one, wait a second, then spawn
+ two, wait a second, then spawn four, and it will
+ continue exponentially until it is spawning 32 children per second. It will
+ stop whenever it satisfies the <code class="directive">MinSpareServers</code>
+ setting.</p>
+
+ <p>Tuning of this parameter should only be necessary on very
+ busy sites. Setting this parameter to a large number is almost
+ always a bad idea.</p>
+
+<h3>See also</h3>
+<ul>
+<li><code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code></li>
+<li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li>
+<li><code class="directive"><a href="../mod/mpm_common.html#minsparethreads">MinSpareThreads</a></code></li>
+</ul>
+</div>
+</div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
+<a href="../en/mod/prefork.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../fr/mod/prefork.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
+<a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../tr/mod/prefork.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</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&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed 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 Libera.chat, or sent to our <a href="https://httpd.apache.org/lists.html">mailing lists</a>.</div>
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