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59 lines
6.1 KiB
Plaintext
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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
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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 Identifier:</a></td><td>mpm_worker_module</td></tr></table></td></tr></table><h2>Summary</h2>
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<p>This Multi-Processing Module (MPM) implements a hybrid
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multi-process multi-threaded server. By using threads to serve
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requests, it is able to serve a large number of requests with
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less system resources than a process-based server. Yet it
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retains much of the stability of a process-based server by
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keeping multiple processes available, each with many threads.</p>
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<p>The most important directives used to control this MPM are
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<a href="mpm_common.html#threadsperchild" class="directive"><code class="directive">ThreadsPerChild</code></a> and
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<a href="mpm_common.html#maxclients" class="directive"><code class="directive">MaxClients</code></a>. By multiplying
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together the value of these directives you define the total number
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of simultaneous connections that the server can handle.</p>
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<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
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ports Apache uses</a></li></ul><h2>How it Works</h2>
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<p>Each process has a fixed
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number of threads. The server adjusts to handle load by
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increasing or decreasing the number of processes.</p>
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<p>A single control process is responsible for launching child
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processes. Each child process creates a fixed number of threads as
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specified in the <a href="mpm_common.html#threadsperchild" class="directive"><code class="directive">ThreadsPerChild</code></a> directive. The
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individual threads then listen for connections and serve them when
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they arrive.</p>
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<p>Apache always tries to maintain a pool of <em>spare</em> or
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idle server threads, which stand ready to serve incoming
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requests. In this way, clients do not need to wait for a new
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threads or processes to be created before their requests can be
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served. Apache assesses the total number of idle threads in all
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processes, and forks or kills processes to keep this number within
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the boundaries specified by <a href="mpm_common.html#minsparethreads" class="directive"><code class="directive">MinSpareThreads</code></a> and <a href="mpm_common.html#maxsparethreads" class="directive"><code class="directive">MaxSpareThreads</code></a>. Since this
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process is very self-regulating, it is rarely necessary to modify
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these directives from their default values. The maximum number of
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clients that may be served simultaneously is determined by
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multiplying the maximum number of server processes that will be
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created (<a href="mpm_common.html#maxclients" class="directive"><code class="directive">MaxClients</code></a>) by
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the number of threads created in each process (<a href="mpm_common.html#threadsperchild" class="directive"><code class="directive">ThreadsPerChild</code></a>).</p>
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<p>While the parent process is usually started as root under Unix
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in order to bind to port 80, the child processes and threads are
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launched by Apache as a less-privileged user. The <a href="mpm_common.html#user" class="directive"><code class="directive">User</code></a> and <a href="mpm_common.html#group" class="directive"><code class="directive">Group</code></a> directives are used to set
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the privileges of the Apache child processes. The child processes
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must be able to read all the content that will be served, but
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should have as few privileges beyond that as possible. In
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addition, unless <a href="../suexec.html">suexec</a> is used,
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these directives also set the privileges which will be inherited
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by CGI scripts.</p>
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<p><a href="mpm_common.html#maxrequestsperchild" class="directive"><code class="directive">MaxRequestsPerChild</code></a>
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controls how frequently the server recycles processes by killing
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old ones and launching new ones.</p>
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<hr/></blockquote><h3 align="center">Apache HTTP Server Version 2.0</h3><a href="./"><img src="../images/index.gif" alt="Index"/></a><a href="../"><img src="../images/home.gif" alt="Home"/></a></body></html> |