1 <?xml version="1.0" encoding="ISO-8859-1"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
3 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
5 This file is generated from xml source: DO NOT EDIT
6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
8 <title>mod_file_cache - Apache HTTP Server Version 2.5</title>
9 <link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
10 <link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
11 <link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
12 <script src="../style/scripts/prettify.min.js" type="text/javascript">
15 <link href="../images/favicon.ico" rel="shortcut icon" /></head>
17 <div id="page-header">
18 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
19 <p class="apache">Apache HTTP Server Version 2.5</p>
20 <img alt="" src="../images/feather.gif" /></div>
21 <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
23 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.5</a> > <a href="./">Modules</a></div>
24 <div id="page-content">
25 <div id="preamble"><h1>Apache Module mod_file_cache</h1>
27 <p><span>Available Languages: </span><a href="../en/mod/mod_file_cache.html" title="English"> en </a> |
28 <a href="../fr/mod/mod_file_cache.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
29 <a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
31 <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>
32 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
33 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>file_cache_module</td></tr>
34 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_file_cache.c</td></tr></table>
39 This module should be used with care. You can easily create a broken
40 site using <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code>, so read this document
44 <p><em>Caching</em> frequently requested files that change very
45 infrequently is a technique for reducing server load.
46 <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> provides two techniques for caching
47 frequently requested <em>static</em> files. Through configuration
48 directives, you can direct <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> to either
49 open then <code>mmap()</code> a file, or to pre-open a file and save
50 the file's open <em>file handle</em>. Both techniques reduce server
51 load when processing requests for these files by doing part of the work
52 (specifically, the file I/O) for serving the file when the
53 server is started rather than during each request.</p>
55 <p>Notice: You cannot use this for speeding up CGI programs or
56 other files which are served by special content handlers. It
57 can only be used for regular files which are usually served by
58 the Apache core content handler.</p>
60 <p>This module is an extension of and borrows heavily from the
61 <code>mod_mmap_static</code> module in Apache 1.3.</p>
63 <div id="quickview"><h3 class="directives">Directives</h3>
65 <li><img alt="" src="../images/down.gif" /> <a href="#cachefile">CacheFile</a></li>
66 <li><img alt="" src="../images/down.gif" /> <a href="#mmapfile">MMapFile</a></li>
70 <li><img alt="" src="../images/down.gif" /> <a href="#using">Using mod_file_cache</a></li>
71 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
72 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
73 <div class="directive-section"><h2><a name="CacheFile" id="CacheFile">CacheFile</a> <a name="cachefile" id="cachefile">Directive</a></h2>
74 <table class="directive">
75 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Cache a list of file handles at startup time</td></tr>
76 <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>
77 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
78 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
79 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr>
81 <p>The <code class="directive">CacheFile</code> directive opens handles to
82 one or more files (given as whitespace separated arguments) and
83 places these handles into the cache at server startup
84 time. Handles to cached files are automatically closed on a server
85 shutdown. When the files have changed on the filesystem, the
86 server should be restarted to re-cache them.</p>
88 <p>Be careful with the <var>file-path</var> arguments: They have
89 to literally match the filesystem path Apache's URL-to-filename
90 translation handlers create. We cannot compare inodes or other
91 stuff to match paths through symbolic links <em>etc.</em>
92 because that again would cost extra <code>stat()</code> system
93 calls which is not acceptable. This module may or may not work
94 with filenames rewritten by <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> or
95 <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
97 <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">CacheFile /usr/local/apache/htdocs/index.html</pre>
101 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
102 <div class="directive-section"><h2><a name="MMapFile" id="MMapFile">MMapFile</a> <a name="mmapfile" id="mmapfile">Directive</a></h2>
103 <table class="directive">
104 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Map a list of files into memory at startup time</td></tr>
105 <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>
106 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
107 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
108 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr>
110 <p>The <code class="directive">MMapFile</code> directive maps one or more files
111 (given as whitespace separated arguments) into memory at server
112 startup time. They are automatically unmapped on a server
113 shutdown. When the files have changed on the filesystem at
114 least a <code>HUP</code> or <code>USR1</code> signal should be send to
115 the server to re-<code>mmap()</code> them.</p>
117 <p>Be careful with the <var>file-path</var> arguments: They have
118 to literally match the filesystem path Apache's URL-to-filename
119 translation handlers create. We cannot compare inodes or other
120 stuff to match paths through symbolic links <em>etc.</em>
121 because that again would cost extra <code>stat()</code> system
122 calls which is not acceptable. This module may or may not work
123 with filenames rewritten by <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> or
124 <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
126 <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">MMapFile /usr/local/apache/htdocs/index.html</pre>
130 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
131 <div class="section">
132 <h2><a name="using" id="using">Using mod_file_cache</a></h2>
134 <p><code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> caches a list of statically
135 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>
137 <p>Not all platforms support both directives. You will receive an error
138 message in the server error log if you attempt to use an
139 unsupported directive. If given an unsupported directive, the
140 server will start but the file will not be cached. On platforms
141 that support both directives, you should experiment with both to
142 see which works best for you.</p>
144 <h3>MMapFile Directive</h3>
146 <p>The <code class="directive"><a href="#mmapfile">MMapFile</a></code>
147 directive of <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> maps a list of
148 statically configured files into memory through the system call
149 <code>mmap()</code>. This system call is available on most modern
150 Unix derivatives, but not on all. There are sometimes system-specific
151 limits on the size and number of files that can be
152 <code>mmap()</code>ed, experimentation is probably the easiest way
155 <p>This <code>mmap()</code>ing is done once at server start or
156 restart, only. So whenever one of the mapped files changes on the
157 filesystem you <em>have</em> to restart the server (see the <a href="../stopping.html">Stopping and Restarting</a> documentation).
158 To reiterate that point: if the files are modified <em>in place</em>
159 without restarting the server you may end up serving requests that
160 are completely bogus. You should update files by unlinking the old
161 copy and putting a new copy in place. Most tools such as
162 <code>rdist</code> and <code>mv</code> do this. The reason why this
163 modules doesn't take care of changes to the files is that this check
164 would need an extra <code>stat()</code> every time which is a waste
165 and against the intent of I/O reduction.</p>
168 <h3>CacheFile Directive</h3>
170 <p>The <code class="directive"><a href="#cachefile">CacheFile</a></code>
171 directive of <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> opens an active
172 <em>handle</em> or <em>file descriptor</em> to the file (or files)
173 listed in the configuration directive and places these open file
174 handles in the cache. When the file is requested, the server
175 retrieves the handle from the cache and passes it to the
176 <code>sendfile()</code> (or <code>TransmitFile()</code> on Windows),
181 <p>This file handle caching is done once at server start or
182 restart, only. So whenever one of the cached files changes on
183 the filesystem you <em>have</em> to restart the server (see the
184 <a href="../stopping.html">Stopping and Restarting</a>
185 documentation). To reiterate that point: if the files are
186 modified <em>in place</em> without restarting the server you
187 may end up serving requests that are completely bogus. You
188 should update files by unlinking the old copy and putting a new
189 copy in place. Most tools such as <code>rdist</code> and
190 <code>mv</code> do this.</p>
193 <div class="note"><h3>Note</h3>
194 <p>Don't bother asking for a directive which recursively
195 caches all the files in a directory. Try this instead... See the
196 <code class="directive"><a href="../mod/core.html#include">Include</a></code> directive, and consider
199 <div class="example"><p><code>
200 find /www/htdocs -type f -print \<br />
201 | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf
206 <div class="bottomlang">
207 <p><span>Available Languages: </span><a href="../en/mod/mod_file_cache.html" title="English"> en </a> |
208 <a href="../fr/mod/mod_file_cache.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
209 <a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
210 </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&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>
211 <script type="text/javascript"><!--//--><![CDATA[//><!--
212 var comments_shortname = 'httpd';
213 var comments_identifier = 'http://httpd.apache.org/docs/trunk/mod/mod_file_cache.html';
215 if (w.location.hostname.toLowerCase() == "httpd.apache.org") {
216 d.write('<div id="comments_thread"><\/div>');
217 var s = d.createElement('script');
218 s.type = 'text/javascript';
220 s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier;
221 (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s);
224 d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>');
226 })(window, document);
227 //--><!]]></script></div><div id="footer">
228 <p class="apache">Copyright 2015 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
229 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!--
230 if (typeof(prettyPrint) !== 'undefined') {