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+<p class="apache">Apache HTTP Server Version 2.4</p>
+<img alt="" src="../images/feather.png" /></div>
+<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
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+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.4</a> &gt; <a href="./">Modules</a></div>
+<div id="page-content">
+<div id="preamble"><h1>Apache Module mod_file_cache</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/mod/mod_file_cache.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../fr/mod/mod_file_cache.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
+<a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
+</div>
+<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Caches a static list of files in memory</td></tr>
+<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
+<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>file_cache_module</td></tr>
+<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_file_cache.c</td></tr></table>
+<h3>Summary</h3>
+
+
+ <div class="warning">
+ This module should be used with care. You can easily create a broken
+ site using <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code>, so read this document
+ carefully.
+ </div>
+
+ <p><em>Caching</em> frequently requested files that change very
+ infrequently is a technique for reducing server load.
+ <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> provides two techniques for caching
+ frequently requested <em>static</em> files. Through configuration
+ directives, you can direct <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> to either
+ open then <code>mmap()</code> a file, or to pre-open a file and save
+ the file's open <em>file handle</em>. Both techniques reduce server
+ load when processing requests for these files by doing part of the work
+ (specifically, the file I/O) for serving the file when the
+ server is started rather than during each request.</p>
+
+ <p>Notice: You cannot use this for speeding up CGI programs or
+ other files which are served by special content handlers. It
+ can only be used for regular files which are usually served by
+ the Apache core content handler.</p>
+
+ <p>This module is an extension of and borrows heavily from the
+ <code>mod_mmap_static</code> module in Apache 1.3.</p>
+</div>
+<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Topics</h3>
+<ul id="topics">
+<li><img alt="" src="../images/down.gif" /> <a href="#using">Using mod_file_cache</a></li>
+</ul><h3 class="directives">Directives</h3>
+<ul id="toc">
+<li><img alt="" src="../images/down.gif" /> <a href="#cachefile">CacheFile</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#mmapfile">MMapFile</a></li>
+</ul>
+<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mod_file_cache">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mod_file_cache">Report a bug</a></li></ul><h3>See also</h3>
+<ul class="seealso">
+<li><a href="#comments_section">Comments</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="using" id="using">Using mod_file_cache</a></h2>
+
+ <p><code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> caches a list of statically
+ configured files via <code class="directive"><a href="#mmapfile">MMapFile</a></code> or <code class="directive"><a href="#cachefile">CacheFile</a></code> directives in the main server configuration.</p>
+
+ <p>Not all platforms support both directives. You will receive an error
+ message in the server error log if you attempt to use an
+ unsupported directive. If given an unsupported directive, the
+ server will start but the file will not be cached. On platforms
+ that support both directives, you should experiment with both to
+ see which works best for you.</p>
+
+ <h3>MMapFile Directive</h3>
+
+ <p>The <code class="directive"><a href="#mmapfile">MMapFile</a></code>
+ directive of <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> maps a list of
+ statically configured files into memory through the system call
+ <code>mmap()</code>. This system call is available on most modern
+ Unix derivatives, but not on all. There are sometimes system-specific
+ limits on the size and number of files that can be
+ <code>mmap()</code>ed, experimentation is probably the easiest way
+ to find out.</p>
+
+ <p>This <code>mmap()</code>ing is done once at server start or
+ restart, only. So whenever one of the mapped files changes on the
+ filesystem you <em>have</em> to restart the server (see the <a href="../stopping.html">Stopping and Restarting</a> documentation).
+ To reiterate that point: if the files are modified <em>in place</em>
+ without restarting the server you may end up serving requests that
+ are completely bogus. You should update files by unlinking the old
+ copy and putting a new copy in place. Most tools such as
+ <code>rdist</code> and <code>mv</code> do this. The reason why this
+ modules doesn't take care of changes to the files is that this check
+ would need an extra <code>stat()</code> every time which is a waste
+ and against the intent of I/O reduction.</p>
+
+
+ <h3>CacheFile Directive</h3>
+
+ <p>The <code class="directive"><a href="#cachefile">CacheFile</a></code>
+ directive of <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> opens an active
+ <em>handle</em> or <em>file descriptor</em> to the file (or files)
+ listed in the configuration directive and places these open file
+ handles in the cache. When the file is requested, the server
+ retrieves the handle from the cache and passes it to the
+ <code>sendfile()</code> (or <code>TransmitFile()</code> on Windows),
+ socket API.</p>
+
+
+
+ <p>This file handle caching is done once at server start or
+ restart, only. So whenever one of the cached files changes on
+ the filesystem you <em>have</em> to restart the server (see the
+ <a href="../stopping.html">Stopping and Restarting</a>
+ documentation). To reiterate that point: if the files are
+ modified <em>in place</em> without restarting the server you
+ may end up serving requests that are completely bogus. You
+ should update files by unlinking the old copy and putting a new
+ copy in place. Most tools such as <code>rdist</code> and
+ <code>mv</code> do this.</p>
+
+
+ <div class="note"><h3>Note</h3>
+ <p>Don't bother asking for a directive which recursively
+ caches all the files in a directory. Try this instead... See the
+ <code class="directive"><a href="../mod/core.html#include">Include</a></code> directive, and consider
+ this command:</p>
+
+ <div class="example"><p><code>
+ find /www/htdocs -type f -print \<br />
+ | sed -e 's/.*/mmapfile &amp;/' &gt; /www/conf/mmap.conf
+ </code></p></div>
+ </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="CacheFile" id="CacheFile">CacheFile</a> <a name="cachefile" id="cachefile">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Cache a list of file handles at startup time</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheFile <var>file-path</var> [<var>file-path</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>Experimental</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr>
+</table>
+ <p>The <code class="directive">CacheFile</code> directive opens handles to
+ one or more files (given as whitespace separated arguments) and
+ places these handles into the cache at server startup
+ time. Handles to cached files are automatically closed on a server
+ shutdown. When the files have changed on the filesystem, the
+ server should be restarted to re-cache them.</p>
+
+ <p>Be careful with the <var>file-path</var> arguments: They have
+ to literally match the filesystem path Apache's URL-to-filename
+ translation handlers create. We cannot compare inodes or other
+ stuff to match paths through symbolic links <em>etc.</em>
+ because that again would cost extra <code>stat()</code> system
+ calls which is not acceptable. This module may or may not work
+ with filenames rewritten by <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> or
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
+
+ <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">CacheFile /usr/local/apache/htdocs/index.html</pre>
+</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="MMapFile" id="MMapFile">MMapFile</a> <a name="mmapfile" id="mmapfile">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Map a list of files into memory at startup time</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MMapFile <var>file-path</var> [<var>file-path</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>Experimental</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr>
+</table>
+ <p>The <code class="directive">MMapFile</code> directive maps one or more files
+ (given as whitespace separated arguments) into memory at server
+ startup time. They are automatically unmapped on a server
+ shutdown. When the files have changed on the filesystem at
+ least a <code>HUP</code> or <code>USR1</code> signal should be send to
+ the server to re-<code>mmap()</code> them.</p>
+
+ <p>Be careful with the <var>file-path</var> arguments: They have
+ to literally match the filesystem path Apache's URL-to-filename
+ translation handlers create. We cannot compare inodes or other
+ stuff to match paths through symbolic links <em>etc.</em>
+ because that again would cost extra <code>stat()</code> system
+ calls which is not acceptable. This module may or may not work
+ with filenames rewritten by <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> or
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
+
+ <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">MMapFile /usr/local/apache/htdocs/index.html</pre>
+</div>
+
+</div>
+</div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/mod/mod_file_cache.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../fr/mod/mod_file_cache.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
+<a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
+</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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