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.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 2.2</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 2.2</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="/ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> 29</div> 30<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> 31<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Experimental</td></tr> 32<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>file_cache_module</td></tr> 33<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_file_cache.c</td></tr></table> 34<h3>Summary</h3> 35 36 37 <div class="warning"> 38 This module should be used with care. You can easily create a broken 39 site using <code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code>, so read this document 40 carefully. 41 </div> 42 43 <p><em>Caching</em> frequently requested files that change very 44 infrequently is a technique for reducing server load. 45 <code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> provides two techniques for caching 46 frequently requested <em>static</em> files. Through configuration 47 directives, you can direct <code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> to either 48 open then <code>mmap()</code> a file, or to pre-open a file and save 49 the file's open <em>file handle</em>. Both techniques reduce server 50 load when processing requests for these files by doing part of the work 51 (specifically, the file I/O) for serving the file when the 52 server is started rather than during each request.</p> 53 54 <p>Notice: You cannot use this for speeding up CGI programs or 55 other files which are served by special content handlers. It 56 can only be used for regular files which are usually served by 57 the Apache core content handler.</p> 58 59 <p>This module is an extension of and borrows heavily from the 60 <code>mod_mmap_static</code> module in Apache 1.3.</p> 61</div> 62<div id="quickview"><h3 class="directives">Directives</h3> 63<ul id="toc"> 64<li><img alt="" src="/images/down.gif" /> <a href="#cachefile">CacheFile</a></li> 65<li><img alt="" src="/images/down.gif" /> <a href="#mmapfile">MMapFile</a></li> 66</ul> 67<h3>Topics</h3> 68<ul id="topics"> 69<li><img alt="" src="/images/down.gif" /> <a href="#using">Using mod_file_cache</a></li> 70</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 71<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 72<div class="section"> 73<h2><a name="using" id="using">Using mod_file_cache</a></h2> 74 75 <p><code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> caches a list of statically 76 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> 77 78 <p>Not all platforms support both directives. You will receive an error 79 message in the server error log if you attempt to use an 80 unsupported directive. If given an unsupported directive, the 81 server will start but the file will not be cached. On platforms 82 that support both directives, you should experiment with both to 83 see which works best for you.</p> 84 85 <h3>MMapFile Directive</h3> 86 87 <p>The <code class="directive"><a href="#mmapfile">MMapFile</a></code> 88 directive of <code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> maps a list of 89 statically configured files into memory through the system call 90 <code>mmap()</code>. This system call is available on most modern 91 Unix derivates, but not on all. There are sometimes system-specific 92 limits on the size and number of files that can be 93 <code>mmap()</code>ed, experimentation is probably the easiest way 94 to find out.</p> 95 96 <p>This <code>mmap()</code>ing is done once at server start or 97 restart, only. So whenever one of the mapped files changes on the 98 filesystem you <em>have</em> to restart the server (see the <a href="/stopping.html">Stopping and Restarting</a> documentation). 99 To reiterate that point: if the files are modified <em>in place</em> 100 without restarting the server you may end up serving requests that 101 are completely bogus. You should update files by unlinking the old 102 copy and putting a new copy in place. Most tools such as 103 <code>rdist</code> and <code>mv</code> do this. The reason why this 104 modules doesn't take care of changes to the files is that this check 105 would need an extra <code>stat()</code> every time which is a waste 106 and against the intent of I/O reduction.</p> 107 108 109 <h3>CacheFile Directive</h3> 110 111 <p>The <code class="directive"><a href="#cachefile">CacheFile</a></code> 112 directive of <code class="module"><a href="/mod/mod_file_cache.html">mod_file_cache</a></code> opens an active 113 <em>handle</em> or <em>file descriptor</em> to the file (or files) 114 listed in the configuration directive and places these open file 115 handles in the cache. When the file is requested, the server 116 retrieves the handle from the cache and passes it to the 117 <code>sendfile()</code> (or <code>TransmitFile()</code> on Windows), 118 socket API.</p> 119 120 121 122 <p>This file handle caching is done once at server start or 123 restart, only. So whenever one of the cached files changes on 124 the filesystem you <em>have</em> to restart the server (see the 125 <a href="/stopping.html">Stopping and Restarting</a> 126 documentation). To reiterate that point: if the files are 127 modified <em>in place</em> without restarting the server you 128 may end up serving requests that are completely bogus. You 129 should update files by unlinking the old copy and putting a new 130 copy in place. Most tools such as <code>rdist</code> and 131 <code>mv</code> do this.</p> 132 133 134 <div class="note"><h3>Note</h3> 135 <p>Don't bother asking for a directive which recursively 136 caches all the files in a directory. Try this instead... See the 137 <code class="directive"><a href="/mod/core.html#include">Include</a></code> directive, and consider 138 this command:</p> 139 140 <div class="example"><p><code> 141 find /www/htdocs -type f -print \<br /> 142 | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf 143 </code></p></div> 144 </div> 145</div> 146<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 147<div class="directive-section"><h2><a name="CacheFile" id="CacheFile">CacheFile</a> <a name="cachefile" id="cachefile">Directive</a></h2> 148<table class="directive"> 149<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Cache a list of file handles at startup time</td></tr> 150<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> 151<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> 152<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr> 153<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr> 154</table> 155 <p>The <code class="directive">CacheFile</code> directive opens handles to 156 one or more files (given as whitespace separated arguments) and 157 places these handles into the cache at server startup 158 time. Handles to cached files are automatically closed on a server 159 shutdown. When the files have changed on the filesystem, the 160 server should be restarted to re-cache them.</p> 161 162 <p>Be careful with the <var>file-path</var> arguments: They have 163 to literally match the filesystem path Apache's URL-to-filename 164 translation handlers create. We cannot compare inodes or other 165 stuff to match paths through symbolic links <em>etc.</em> 166 because that again would cost extra <code>stat()</code> system 167 calls which is not acceptable. This module may or may not work 168 with filenames rewritten by <code class="module"><a href="/mod/mod_alias.html">mod_alias</a></code> or 169 <code class="module"><a href="/mod/mod_rewrite.html">mod_rewrite</a></code>.</p> 170 171 <div class="example"><h3>Example</h3><p><code> 172 CacheFile /usr/local/apache/htdocs/index.html 173 </code></p></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><p><code> 202 MMapFile /usr/local/apache/htdocs/index.html 203 </code></p></div> 204 205</div> 206</div> 207<div class="bottomlang"> 208<p><span>Available Languages: </span><a href="/en/mod/mod_file_cache.html" title="English"> en </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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