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 7 --> 8<title>mod_file_cache - Apache HTTP Server</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"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body> 17<div id="page-header"> 18<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.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 2.4</p> 20<img alt="" src="/images/feather.gif" /></div> 21<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 22<div id="path"> 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 2.4</a> > <a href="./">Modules</a></div> 24<div id="page-content"> 25<div id="preamble"><h1>Apache Module mod_file_cache</h1> 26<div class="toplang"> 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="Fran�ais"> fr </a> | 29<a href="/ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> 30</div> 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> 35<h3>Summary</h3> 36 37 38 <div class="warning"> 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 41 carefully. 42 </div> 43 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> 54 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> 59 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> 62</div> 63<div id="quickview"><h3 class="directives">Directives</h3> 64<ul id="toc"> 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> 67</ul> 68<h3>Topics</h3> 69<ul id="topics"> 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="section"> 74<h2><a name="using" id="using">Using mod_file_cache</a></h2> 75 76 <p><code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> caches a list of statically 77 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> 78 79 <p>Not all platforms support both directives. You will receive an error 80 message in the server error log if you attempt to use an 81 unsupported directive. If given an unsupported directive, the 82 server will start but the file will not be cached. On platforms 83 that support both directives, you should experiment with both to 84 see which works best for you.</p> 85 86 <h3>MMapFile Directive</h3> 87 88 <p>The <code class="directive"><a href="#mmapfile">MMapFile</a></code> 89 directive of <code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> maps a list of 90 statically configured files into memory through the system call 91 <code>mmap()</code>. This system call is available on most modern 92 Unix derivatives, but not on all. There are sometimes system-specific 93 limits on the size and number of files that can be 94 <code>mmap()</code>ed, experimentation is probably the easiest way 95 to find out.</p> 96 97 <p>This <code>mmap()</code>ing is done once at server start or 98 restart, only. So whenever one of the mapped files changes on the 99 filesystem you <em>have</em> to restart the server (see the <a href="/stopping.html">Stopping and Restarting</a> documentation). 100 To reiterate that point: if the files are modified <em>in place</em> 101 without restarting the server you may end up serving requests that 102 are completely bogus. You should update files by unlinking the old 103 copy and putting a new copy in place. Most tools such as 104 <code>rdist</code> and <code>mv</code> do this. The reason why this 105 modules doesn't take care of changes to the files is that this check 106 would need an extra <code>stat()</code> every time which is a waste 107 and against the intent of I/O reduction.</p> 108 109 110 <h3>CacheFile Directive</h3> 111 112 <p>The <code class="directive"><a href="#cachefile">CacheFile</a></code> 113 directive of <code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> opens an active 114 <em>handle</em> or <em>file descriptor</em> to the file (or files) 115 listed in the configuration directive and places these open file 116 handles in the cache. When the file is requested, the server 117 retrieves the handle from the cache and passes it to the 118 <code>sendfile()</code> (or <code>TransmitFile()</code> on Windows), 119 socket API.</p> 120 121 122 123 <p>This file handle caching is done once at server start or 124 restart, only. So whenever one of the cached files changes on 125 the filesystem you <em>have</em> to restart the server (see the 126 <a href="/stopping.html">Stopping and Restarting</a> 127 documentation). To reiterate that point: if the files are 128 modified <em>in place</em> without restarting the server you 129 may end up serving requests that are completely bogus. You 130 should update files by unlinking the old copy and putting a new 131 copy in place. Most tools such as <code>rdist</code> and 132 <code>mv</code> do this.</p> 133 134 135 <div class="note"><h3>Note</h3> 136 <p>Don't bother asking for a directive which recursively 137 caches all the files in a directory. Try this instead... See the 138 <code class="directive"><a href="/mod/core.html#include">Include</a></code> directive, and consider 139 this command:</p> 140 141 <div class="example"><p><code> 142 find /www/htdocs -type f -print \<br /> 143 | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf 144 </code></p></div> 145 </div> 146</div> 147<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 148<div class="directive-section"><h2><a name="CacheFile" id="CacheFile">CacheFile</a> <a name="cachefile" id="cachefile">Directive</a></h2> 149<table class="directive"> 150<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Cache a list of file handles at startup time</td></tr> 151<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> 152<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 153<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr> 154<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr> 155</table> 156 <p>The <code class="directive">CacheFile</code> directive opens handles to 157 one or more files (given as whitespace separated arguments) and 158 places these handles into the cache at server startup 159 time. Handles to cached files are automatically closed on a server 160 shutdown. When the files have changed on the filesystem, the 161 server should be restarted to re-cache them.</p> 162 163 <p>Be careful with the <var>file-path</var> arguments: They have 164 to literally match the filesystem path Apache's URL-to-filename 165 translation handlers create. We cannot compare inodes or other 166 stuff to match paths through symbolic links <em>etc.</em> 167 because that again would cost extra <code>stat()</code> system 168 calls which is not acceptable. This module may or may not work 169 with filenames rewritten by <code class="module"><a href="/mod/mod_alias.html">mod_alias</a></code> or 170 <code class="module"><a href="/mod/mod_rewrite.html">mod_rewrite</a></code>.</p> 171 172 <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">CacheFile /usr/local/apache/htdocs/index.html</pre> 173</div> 174 175</div> 176<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 177<div class="directive-section"><h2><a name="MMapFile" id="MMapFile">MMapFile</a> <a name="mmapfile" id="mmapfile">Directive</a></h2> 178<table class="directive"> 179<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Map a list of files into memory at startup time</td></tr> 180<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> 181<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 182<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr> 183<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr> 184</table> 185 <p>The <code class="directive">MMapFile</code> directive maps one or more files 186 (given as whitespace separated arguments) into memory at server 187 startup time. They are automatically unmapped on a server 188 shutdown. When the files have changed on the filesystem at 189 least a <code>HUP</code> or <code>USR1</code> signal should be send to 190 the server to re-<code>mmap()</code> them.</p> 191 192 <p>Be careful with the <var>file-path</var> arguments: They have 193 to literally match the filesystem path Apache's URL-to-filename 194 translation handlers create. We cannot compare inodes or other 195 stuff to match paths through symbolic links <em>etc.</em> 196 because that again would cost extra <code>stat()</code> system 197 calls which is not acceptable. This module may or may not work 198 with filenames rewritten by <code class="module"><a href="/mod/mod_alias.html">mod_alias</a></code> or 199 <code class="module"><a href="/mod/mod_rewrite.html">mod_rewrite</a></code>.</p> 200 201 <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">MMapFile /usr/local/apache/htdocs/index.html</pre> 202</div> 203 204</div> 205</div> 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="Fran�ais"> 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. 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