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113 lines
4.5 KiB
XML
113 lines
4.5 KiB
XML
<?xml version='1.0' encoding='UTF-8' ?>
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<!DOCTYPE manualpage SYSTEM "./style/manualpage.dtd">
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<?xml-stylesheet type="text/xsl" href="./style/manual.en.xsl"?>
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<!-- $LastChangedRevision$ -->
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<!--
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Copyright 2002-2005 The Apache Software Foundation or its licensors, as
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applicable.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<manualpage metafile="mpm.xml.meta">
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<title>Multi-Processing Modules (MPMs)</title>
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<summary>
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<p>This document describes what a Multi-Processing Module is and
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how they are used by the Apache HTTP Server.</p>
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</summary>
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<section id="introduction"><title>Introduction</title>
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<p>The Apache HTTP Server is designed to be a powerful and
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flexible web server that can work on a very wide variety of
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platforms in a range of different environments. Different
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platforms and different environments often require different
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features, or may have different ways of implementing the same
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feature most efficiently. Apache has always accommodated a wide
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variety of environments through its modular design. This design
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allows the webmaster to choose which features will be included
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in the server by selecting which modules to load either at
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compile-time or at run-time.</p>
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<p>Apache 2.0 extends this modular design to the most basic
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functions of a web server. The server ships with a selection of
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Multi-Processing Modules (MPMs) which are responsible for
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binding to network ports on the machine, accepting requests,
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and dispatching children to handle the requests.</p>
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<p>Extending the modular design to this level of the server
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allows two important benefits:</p>
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<ul>
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<li>Apache can more cleanly and efficiently support a wide
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variety of operating systems. In particular, the Windows
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version of Apache is now much more efficient, since
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<module>mpm_winnt</module> can use native
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networking features in place of the POSIX layer used in
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Apache 1.3. This benefit also extends to other operating
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systems that implement specialized MPMs.</li>
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<li>The server can be better customized for the needs of the
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particular site. For example, sites that need a great deal of
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scalability can choose to use a threaded MPM like
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<module>worker</module> or <module>event</module>, while sites requiring
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stability or compatibility with older software can use a
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<module>prefork</module>.</li>
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</ul>
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<p>At the user level, MPMs appear much like other Apache
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modules. The main difference is that one and only one MPM must
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be loaded into the server at any time. The list of available
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MPMs appears on the <a href="mod/">module index page</a>.</p>
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</section>
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<section id="choosing"><title>Choosing an MPM</title>
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<p>MPMs must be chosen during configuration, and compiled into
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the server. Compilers are capable of optimizing a lot of
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functions if threads are used, but only if they know that
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threads are being used.</p>
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<p>To actually choose the desired MPM, use the argument
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<code>--with-mpm=<em>NAME</em></code> with the
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<program>configure</program> script. <em>NAME</em> is the name of the
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desired MPM.</p>
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<p>Once the server has been compiled, it is possible to
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determine which MPM was chosen by using <code>./httpd
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-l</code>. This command will list every module that is compiled
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into the server, including the MPM.</p>
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</section>
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<section id="defaults"><title>MPM Defaults</title>
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<p>The following table lists the default MPMs for various operating
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systems. This will be the MPM selected if you do not make another
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choice at compile-time.</p>
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<table>
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<columnspec><column width=".2"/><column width=".2"/></columnspec>
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<tr><td>BeOS</td><td><module>beos</module></td></tr>
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<tr><td>Netware</td><td><module>mpm_netware</module></td></tr>
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<tr><td>OS/2</td><td><module>mpmt_os2</module></td></tr>
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<tr><td>Unix</td><td><module>prefork</module></td></tr>
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<tr><td>Windows</td><td><module>mpm_winnt</module></td></tr>
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</table>
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</section>
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</manualpage>
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