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127 lines
5.2 KiB
HTML
127 lines
5.2 KiB
HTML
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<meta name="generator" content="HTML Tidy, see www.w3.org" />
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<title>Apache module mod_mmap_static</title>
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<!--#include virtual="header.html" -->
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<h1 align="CENTER">Module mod_mmap_static</h1>
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<p>This module provides mmap()ing of a statically configured
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list of frequently requested but not changed files.</p>
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<p><a href="module-dict.html#Status"
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rel="Help"><strong>Status:</strong></a> Experimental<br />
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<a href="module-dict.html#SourceFile"
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rel="Help"><strong>Source File:</strong></a>
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mod_mmap_static.c<br />
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<a href="module-dict.html#ModuleIdentifier"
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rel="Help"><strong>Module Identifier:</strong></a>
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mmap_static_module</p>
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<h2>Summary</h2>
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<p>This is an <strong>experimental</strong> module and should
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be used with care. You can easily create a broken site using
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this module, read this document carefully.
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<code>mod_mmap_static</code> maps a list of statically
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configured files (via <code>MMapFile</code> directives in the
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main server configuration) into memory through the system call
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<code>mmap()</code>. This system call is available on most
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modern Unix derivates, but not on all. There are sometimes
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system-specific limits on the size and number of files that can
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be mmap()d, experimentation is probably the easiest way to find
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out.</p>
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<p>This mmap()ing is done once at server start or restart,
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only. So whenever one of the mapped files changes on the
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filesystem you <em>have</em> to restart the server by at least
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sending it a HUP or USR1 signal (see the <a
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href="../stopping.html">Stopping and Restarting</a>
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documentation). To reiterate that point: if the files are
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modified <em>in place</em> without restarting the server you
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may end up serving requests that are completely bogus. You
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should update files by unlinking the old copy and putting a new
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copy in place. Most tools such as <code>rdist</code> and
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<code>mv</code> do this. The reason why this modules doesn't
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take care of changes to the files is that this check would need
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an extra <code>stat()</code> every time which is a waste and
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against the intent of I/O reduction.</p>
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<h2>Directives</h2>
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<ul>
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<li><a href="#mmapfile">MMapFile</a></li>
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</ul>
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<hr />
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<h2><a id="mmapfile" name="mmapfile">MMapFile</a>
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directive</h2>
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<p><a href="directive-dict.html#Syntax"
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rel="Help"><strong>Syntax:</strong></a> MMapFile
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<em>filename</em> [<em>filename</em>] ...<br />
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<a href="directive-dict.html#Default"
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rel="Help"><strong>Default:</strong></a> <em>None</em><br />
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<a href="directive-dict.html#Context"
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rel="Help"><strong>Context:</strong></a> server-config<br />
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<a href="directive-dict.html#Override"
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rel="Help"><strong>Override:</strong></a> <em>Not
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applicable</em><br />
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<a href="directive-dict.html#Status"
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rel="Help"><strong>Status:</strong></a> Experimental<br />
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<a href="directive-dict.html#Module"
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rel="Help"><strong>Module:</strong></a> mod_mmap_static<br />
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<a href="directive-dict.html#Compatibility"
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rel="Help"><strong>Compatibility:</strong></a> Only available
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in Apache 1.3 or later</p>
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<p>The <code>MMapFile</code> directive maps one or more files
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(given as whitespace separated arguments) into memory at server
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startup time. They are automatically unmapped on a server
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shutdown. When the files have changed on the filesystem at
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least a HUP or USR1 signal should be send to the server to
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re-mmap them.</p>
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<p>Be careful with the <em>filename</em> arguments: They have
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to literally match the filesystem path Apache's URL-to-filename
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translation handlers create. We cannot compare inodes or other
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stuff to match paths through symbolic links <em>etc.</em>
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because that again would cost extra <code>stat()</code> system
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calls which is not acceptable. This module may or may not work
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with filenames rewritten by <code>mod_alias</code> or
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<code>mod_rewrite</code>... it is an experiment after all.</p>
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<p>Notice: You cannot use this for speeding up CGI programs or
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other files which are served by special content handlers. It
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can only be used for regular files which are usually served by
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the Apache core content handler.</p>
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Example:
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<pre>
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MMapFile /usr/local/apache/htdocs/index.html
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</pre>
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<p><strong>Note</strong>: don't bother asking for a for a
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<code>MMapDir</code> directive which recursively maps all the
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files in a directory. Use Unix the way it was meant to be used.
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For example, see the <a href="core.html#include">Include</a>
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directive, and consider this command:</p>
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<pre>
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find /www/htdocs -type f -print \
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| sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf
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</pre>
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