1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
|
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
This file is generated from xml source: DO NOT EDIT
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-->
<title>mod_file_cache - Apache HTTP Server</title>
<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
<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" />
<script src="../style/scripts/prettify.js" type="text/javascript">
</script>
<link href="../images/favicon.ico" rel="shortcut icon" /></head>
<body>
<div id="page-header">
<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>
<p class="apache">Apache HTTP Server Version 2.5</p>
<img alt="" src="../images/feather.gif" /></div>
<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
<div id="path">
<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>
<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"> en </a> |
<a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </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"><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" /> <a href="#using">Using mod_file_cache</a></li>
</ul><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 &/' > /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"> en </a> |
<a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </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&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>
<script type="text/javascript"><!--//--><![CDATA[//><!--
var comments_shortname = 'httpd';
var comments_identifier = 'http://httpd.apache.org/docs/trunk/mod/mod_file_cache.html';
(function(w, d) {
if (w.location.hostname.toLowerCase() == "httpd.apache.org") {
d.write('<div id="comments_thread"><\/div>');
var s = d.createElement('script');
s.type = 'text/javascript';
s.async = true;
s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier;
(d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s);
}
else {
d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>');
}
})(window, document);
//--><!]]></script></div><div id="footer">
<p class="apache">Copyright 2013 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>
<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></div><script type="text/javascript"><!--//--><![CDATA[//><!--
if (typeof(prettyPrint) !== 'undefined') {
prettyPrint();
}
//--><!]]></script>
</body></html>
|
