</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 mod_file_cache, so read this
- document carefully.
-</div>
+ 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.
- mod_file_cache provides two techniques for caching frequently
- requested <em>static</em> files. Through configuration
- directives, you can direct mod_file_cache to either open then
- mmap()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
+ <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>
the Apache core content handler.</p>
<p>This module is an extension of and borrows heavily from the
- mod_mmap_static module in Apache 1.3.</p>
+ <code>mod_mmap_static</code> module in Apache 1.3.</p>
</div><div id="quickview"><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>Topics</h3><ul id="topics"><li><img alt="" src="../images/down.gif" /> Using mod_file_cache</li></ul></div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="section"><h2>Using mod_file_cache</h2>
+</ul><h3>Topics</h3><ul id="topics"><li><img alt="" src="../images/down.gif" /> <a href="#using">Using mod_file_cache</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>
+ 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. For example, Apache
on Windows does not currently support the <code class="directive"><a href="#mmapstatic">MMapStatic</a></code> directive, while
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 derivates, but not on all. There are sometimes
- system-specific limits on the size and number of files that can be
- mmap()d, experimentation is probably the easiest way to find
- out.</p>
-
- <p>This mmap()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
- sendfile() (or TransmitFile() on Windows), socket API.</p>
-
- <p>Insert more details about sendfile 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> Don't bother asking for a 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:
-<div class="example"><p><code>
- find /www/htdocs -type f -print \ <br />
- | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf
-</code></p></div>
-</div>
-
+ <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 derivates, 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 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 &/' > /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 /></tr><tr><th><a href="directive-dict.html#Syntax">Syntax:
- </a></th><td><code>CacheFile
- <em>file-path</em> [<em>file-path</em>] ...</code></td></tr><tr><th><a href="directive-dict.html#Context">Context:
+ </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>
shutdown. When the files have changed on the filesystem, the
server should be restarted to to re-cache them.</p>
- <p>Be careful with the <em>file-path</em> arguments: They have
+ <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>
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><p><code>
- CacheFile /usr/local/apache/htdocs/index.html
-</code></p></div>
+
<div class="example"><h3>Example</h3><p><code>
+ CacheFile /usr/local/apache/htdocs/index.html
+ </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="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
/></tr><tr><th><a href="directive-dict.html#Syntax">Syntax:
- </a></th><td><code>MMapFile <
em>file-path</em> [<em>file-path</em>] ...</code></td></tr><tr><th><a href="directive-dict.html#Context">Context:
+ </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>
(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 HUP or USR1 signal should be send to the server to
- re-mmap them.</p>
+ 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 <em>file-path</em> arguments: They have
+ <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>
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><p><code>
- MMapFile /usr/local/apache/htdocs/index.html
-</code></p></div>
+
<div class="example"><h3>Example</h3><p><code>
+ MMapFile /usr/local/apache/htdocs/index.html
+ </code></p></div>
</div></div><div id="footer"><p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p><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></div></body></html>
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