<html><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><!--
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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 nowrap="nowrap" 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 nowrap="nowrap"><a href="module-dict.html#Status" class="help">Status:
                      </a></td><td>MPM</td></tr><tr><td nowrap="nowrap"><a href="module-dict.html#ModuleIdentifier" class="help">Module&nbsp;Identifier:
                        </a></td><td>mpm_worker_module</td></tr></table></td></tr></table><h2>Summary</h2>
    <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
    less system resources than a process-based server.  Yet 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="../mod/mpm_common.html#threadsperchild" class="directive"><code class="directive">ThreadsPerChild</code></a> and
    <a href="../mod/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="../mod/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
    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="../mod/mpm_common.html#minsparethreads" class="directive"><code class="directive">MinSpareThreads</code></a> and <a href="../mod/mpm_common.html#maxsparethreads" class="directive"><code class="directive">MaxSpareThreads</code></a>. 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="../mod/mpm_common.html#maxclients" class="directive"><code class="directive">MaxClients</code></a>) by
    the number of threads created in each process (<a href="../mod/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="../mod/mpm_common.html#user" class="directive"><code class="directive">User</code></a> and <a href="../mod/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
    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,
    these directives also set the privileges which will be inherited
    by CGI scripts.</p>

    <p><a href="../mod/mpm_common.html#maxrequestsperchild" class="directive"><code class="directive">MaxRequestsPerChild</code></a>
    controls how frequently the server recycles processes by killing
    old ones and launching new ones.</p>
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