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| <title>perchild - Apache HTTP Server</title> |
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| <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> |
| <p class="apache">Apache HTTP Server Version 2.0</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 2.0</a> > <a href="./">Modules</a></div> |
| <div id="page-content"> |
| <div class="retired"><h4>Please note</h4> |
| <p>This document refers to the <strong>2.0</strong> version of Apache httpd, which <strong>is no longer maintained</strong>. Upgrade, and refer to the current version of httpd instead, documented at:</p> |
| <ul><li><a href="http://httpd.apache.org/docs/current/">Current release version of Apache HTTP Server documentation</a></li></ul><p>You may follow <a href="http://httpd.apache.org/docs/current/mod/perchild.html">this link</a> to go to the current version of this document.</p></div><div id="preamble"><h1>Apache MPM perchild</h1> |
| <div class="toplang"> |
| <p><span>Available Languages: </span><a href="../en/mod/perchild.html" title="English"> en </a></p> |
| </div> |
| <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Multi-Processing Module allowing for daemon processes serving |
| requests to be assigned a variety of different userids</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_perchild_module</td></tr> |
| <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>perchild.c</td></tr></table> |
| <h3>Summary</h3> |
| |
| <div class="warning"> |
| This module is not functional. Development of this module is not |
| complete and is not currently active. Do not use |
| <code class="module"><a href="../mod/perchild.html">perchild</a></code> unless you are a programmer willing to |
| help fix it. |
| </div> |
| |
| <p>This Multi-Processing Module (MPM) implements a hybrid |
| multi-process, multi-threaded web server. A fixed number of |
| processes create threads to handle requests. Fluctuations in |
| load are handled by increasing or decreasing the number of |
| threads in each process.</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/down.gif" /> <a href="#assignuserid">AssignUserID</a></li> |
| <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#bs2000account">BS2000Account</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#childperuserid">ChildPerUserID</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#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/down.gif" /> <a href="#maxthreadsperchild">MaxThreadsPerChild</a></li> |
| <li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#minsparethreads">MinSpareThreads</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#numservers">NumServers</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#startthreads">StartThreads</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#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 launches the number of child processes |
| indicated by the <code class="directive"><a href="#numservers">NumServers</a></code> |
| directive at server startup. Each child process creates threads as |
| specified in the <code class="directive"><a href="../mod/mpm_common.html#startthreads">StartThreads</a></code> directive. |
| The individual threads then |
| listen for connections and serve them 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 new |
| threads to be created. For each child process, Apache assesses |
| the number of idle threads and creates or destroys threads 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 number of server processes |
| that will be created (<code class="directive"><a href="#numservers">NumServers</a></code>) by the maximum |
| number of threads created in each process |
| (<code class="directive"><a href="../mod/mpm_common.html#maxthreadsperchild">MaxThreadsPerChild</a></code>).</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 |
| <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> |
| |
| <h3><a name="user-ids" id="user-ids">Working with different user-IDs</a></h3> |
| <p>The <code class="module"><a href="../mod/perchild.html">perchild</a></code> MPM adds the extra ability to |
| specify that particular processes should serve requests under |
| different user-IDs. These user-IDs can then be associated with |
| specific virtual hosts. You have to use one <code class="directive"><a href="#childperuserid">ChildPerUserID</a></code> directive for |
| every user/group combination you want to be run. Then you can tie |
| particular virtual hosts to that user and group IDs.</p> |
| |
| <p>The following example runs 7 child processes. Two of them are run |
| under <code>user1</code>/<code>group1</code>. The next four are run |
| under <code>user2</code>/<code>group2</code> and the remaining |
| process uses 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> |
| of the main server:</p> |
| |
| <div class="example"><h3>Global config</h3><p><code> |
| NumServers 7<br /> |
| ChildPerUserID user1 group1 2<br /> |
| ChildPerUserID user2 group2 4 |
| </code></p></div> |
| |
| <p>Using unbalanced numbers of processes as above is useful, if the |
| particular virtual hosts produce different load. The assignment to |
| the virtual hosts is easily done as in the example below. In |
| conclusion with the example above the following assumes, that |
| <code>server2</code> has to serve about twice of the hits of |
| <code>server1</code>.</p> |
| |
| <div class="example"><h3>Example</h3><p><code> |
| NameVirtualHost *<br /> |
| <br /> |
| <VirtualHost *><br /> |
| <span class="indent"> |
| ServerName fallbackhost<br /> |
| # no assignment; use fallback<br /> |
| </span> |
| </VirtualHost><br /> |
| <br /> |
| <VirtualHost *><br /> |
| <span class="indent"> |
| ServerName server1<br /> |
| AssignUserID user1 group1<br /> |
| </span> |
| </VirtualHost><br /> |
| <br /> |
| <VirtualHost *><br /> |
| <span class="indent"> |
| ServerName server2<br /> |
| AssignUserID user2 group2<br /> |
| </span> |
| </VirtualHost> |
| </code></p></div> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="AssignUserID" id="AssignUserID">AssignUserID</a> <a name="assignuserid" id="assignuserid">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Tie a virtual host to a user and group ID</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AssignUserID <var>user-id</var> <var>group-id</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>virtual host</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>perchild</td></tr> |
| </table> |
| <p>Tie a virtual host to a specific user/group combination. Requests |
| addressed to the virtual host where this directive appears will be |
| served by a process running with the specified user and group ID.</p> |
| |
| <p>The user and group ID has to be assigned to a number of children |
| in the global server config using the <code class="directive"><a href="#childperuserid">ChildPerUserID</a></code> directive. See the section above for a |
| <a href="#user-ids">configuration example</a>.</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="ChildPerUserID" id="ChildPerUserID">ChildPerUserID</a> <a name="childperuserid" id="childperuserid">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify user ID and group ID for a number of child |
| processes</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ChildPerUserID <var>user-id</var> <var>group-id</var> |
| <var>num-children</var></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>perchild</td></tr> |
| </table> |
| <p>Specify a user ID and group ID for a number of child processes. |
| The third argument, <var>num-children</var>, is the number of child |
| processes to start with the specified user and group. It does |
| <em>not</em> represent a specific child number. In order to use this |
| directive, the server must be run initially as <code>root</code>. |
| If you start the server as a non-root user, it will fail to change |
| to the lesser privileged user.</p> |
| |
| <p>If the total number of child processes, found by totaling all of the |
| third arguments to all <code class="directive">ChildPerUserID</code> directives |
| in the config file, is less than <code class="directive"><a href="#numservers">NumServers</a></code>, then all remaining children will inherit 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> settings from the main server. |
| See the section above for a <a href="#user-ids">configuration |
| example</a>.</p> |
| |
| <div class="warning"><h3>Security</h3> |
| <p>Don't set <var>user-id</var> (or <var>group-id</var>) to |
| <code>root</code> unless you know exactly what you are doing, and |
| what the dangers are.</p> |
| </div> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="MaxThreadsPerChild" id="MaxThreadsPerChild">MaxThreadsPerChild</a> <a name="maxthreadsperchild" id="maxthreadsperchild">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of threads per child process</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxThreadsPerChild <var>number</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxThreadsPerChild 64</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>perchild</td></tr> |
| </table> |
| <p>This directive sets the maximum number of threads that will be |
| created in each child process. To increase this value beyond its |
| default, it is necessary to change the value of the <code class="directive"><a href="../mod/mpm_common.html#threadlimit">ThreadLimit</a></code> directive and stop and |
| re-start the server.</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="NumServers" id="NumServers">NumServers</a> <a name="numservers" id="numservers">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Total number of children alive at the same time</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>NumServers <var>number</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>NumServers 2</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>perchild</td></tr> |
| </table> |
| <p>The <code class="directive">NumServers</code> directive determines the number |
| of children alive at the same time. This number should be large enough to |
| handle the requests for the entire site. To increase this value beyond the |
| value of <code>8</code>, it is necessary to change the value of the |
| <code class="directive"><a href="../mod/mpm_common.html#serverlimit">ServerLimit</a></code> directive and stop |
| and re-start the server. See the section above for a <a href="#user-ids">configuration example</a>.</p> |
| |
| </div> |
| </div> |
| <div class="bottomlang"> |
| <p><span>Available Languages: </span><a href="../en/mod/perchild.html" title="English"> en </a></p> |
| </div><div id="footer"> |
| <p class="apache">Copyright 2013 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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