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8 <title>mod_cache_disk - Apache HTTP Server</title>
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19 <p class="apache">Apache HTTP Server Version 2.5</p>
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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_cache_disk</h1>
27 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English"> en </a> |
28 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
29 <a href="../ja/mod/mod_cache_disk.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
30 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
32 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Disk based storage module for the HTTP caching filter.</td></tr>
33 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
34 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>cache_disk_module</td></tr>
35 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_cache_disk.c</td></tr></table>
38 <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> implements a disk based storage
39 manager for <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>.</p>
41 <p>The headers and bodies of cached responses are stored separately on
42 disk, in a directory structure derived from the md5 hash of the cached
45 <p>Multiple content negotiated responses can be stored concurrently,
46 however the caching of partial content is not yet supported by this
49 <p>Atomic cache updates to both header and body files are achieved
50 without the need for locking by storing the device and inode numbers of
51 the body file within the header file. This has the side effect that
52 cache entries manually moved into the cache will be ignored.</p>
54 <p>The <code class="program"><a href="../programs/htcacheclean.html">htcacheclean</a></code> tool is provided to list cached
55 URLs, remove cached URLs, or to maintain the size of the disk cache
56 within size and/or inode limits. The tool can be run on demand, or
57 can be daemonized to offer continuous monitoring of directory sizes.</p>
59 <div class="note"><h3>Note:</h3>
60 <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> requires the services of
61 <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>, which must be
62 loaded before mod_cache_disk.</p>
64 <div class="note"><h3>Note:</h3>
65 <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> uses the sendfile feature to
66 serve files from the cache when supported by the platform, and
67 when enabled with <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code>.
68 However, per-directory and .htaccess configuration of
69 <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> are ignored by
70 <code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> as the corresponding settings are not
71 available to the module when a request is being served from the
75 <div id="quickview"><h3 class="directives">Directives</h3>
77 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlength">CacheDirLength</a></li>
78 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlevels">CacheDirLevels</a></li>
79 <li><img alt="" src="../images/down.gif" /> <a href="#cachemaxfilesize">CacheMaxFileSize</a></li>
80 <li><img alt="" src="../images/down.gif" /> <a href="#cacheminfilesize">CacheMinFileSize</a></li>
81 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadsize">CacheReadSize</a></li>
82 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadtime">CacheReadTime</a></li>
83 <li><img alt="" src="../images/down.gif" /> <a href="#cacheroot">CacheRoot</a></li>
87 <li><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code></li>
88 <li><code class="module"><a href="../mod/mod_cache_socache.html">mod_cache_socache</a></code></li>
89 <li><a href="../caching.html">Caching Guide</a></li>
90 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
92 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
93 <div class="directive-section"><h2><a name="CacheDirLength" id="CacheDirLength">CacheDirLength</a> <a name="cachedirlength" id="cachedirlength">Directive</a></h2>
94 <table class="directive">
95 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of characters in subdirectory names</td></tr>
96 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLength <var>length</var></code></td></tr>
97 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLength 2</code></td></tr>
98 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
99 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
100 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
102 <p>The <code class="directive">CacheDirLength</code> directive sets the number
103 of characters for each subdirectory name in the cache hierarchy. It can
104 be used in conjunction with <code class="directive">CacheDirLevels</code> to
105 determine the approximate structure of your cache hierarchy.</p>
106 <p>A high value for <code class="directive">CacheDirLength</code> combined
107 with a low value for <code class="directive">CacheDirLevels</code> will result in
108 a relatively flat hierarchy, with a large number of subdirectories at each
112 <p>The result of <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code>* <code class="directive">CacheDirLength</code>
113 must not be higher than 20.</p>
118 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
119 <div class="directive-section"><h2><a name="CacheDirLevels" id="CacheDirLevels">CacheDirLevels</a> <a name="cachedirlevels" id="cachedirlevels">Directive</a></h2>
120 <table class="directive">
121 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of levels of subdirectories in the
123 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLevels <var>levels</var></code></td></tr>
124 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLevels 2</code></td></tr>
125 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
126 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
127 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
129 <p>The <code class="directive">CacheDirLevels</code> directive sets the number
130 of subdirectory levels in the cache. Cached data will be saved this
131 many directory levels below the <code class="directive"><a href="#cacheroot">CacheRoot</a></code> directory.</p>
132 <p>A high value for <code class="directive">CacheDirLevels</code> combined
133 with a low value for <code class="directive">CacheDirLength</code> will result in
134 a relatively deep hierarchy, with a small number of subdirectories at each
138 <p>The result of <code class="directive">CacheDirLevels</code>*
139 <code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> must
140 not be higher than 20.</p>
145 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
146 <div class="directive-section"><h2><a name="CacheMaxFileSize" id="CacheMaxFileSize">CacheMaxFileSize</a> <a name="cachemaxfilesize" id="cachemaxfilesize">Directive</a></h2>
147 <table class="directive">
148 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum size (in bytes) of a document to be placed in the
150 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMaxFileSize <var>bytes</var></code></td></tr>
151 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMaxFileSize 1000000</code></td></tr>
152 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
153 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
154 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
156 <p>The <code class="directive">CacheMaxFileSize</code> directive sets the
157 maximum size, in bytes, for a document to be considered for storage in
160 <pre class="prettyprint lang-config">
161 CacheMaxFileSize 64000
166 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
167 <div class="directive-section"><h2><a name="CacheMinFileSize" id="CacheMinFileSize">CacheMinFileSize</a> <a name="cacheminfilesize" id="cacheminfilesize">Directive</a></h2>
168 <table class="directive">
169 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of a document to be placed in the
171 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMinFileSize <var>bytes</var></code></td></tr>
172 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMinFileSize 1</code></td></tr>
173 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
174 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
175 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
177 <p>The <code class="directive">CacheMinFileSize</code> directive sets the
178 minimum size, in bytes, for a document to be considered for storage
181 <pre class="prettyprint lang-config">
187 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
188 <div class="directive-section"><h2><a name="CacheReadSize" id="CacheReadSize">CacheReadSize</a> <a name="cachereadsize" id="cachereadsize">Directive</a></h2>
189 <table class="directive">
190 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of the document to read and be cached
191 before sending the data downstream</td></tr>
192 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadSize <var>bytes</var></code></td></tr>
193 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadSize 0</code></td></tr>
194 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
195 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
196 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
198 <p>The <code class="directive">CacheReadSize</code> directive sets the
199 minimum amount of data, in bytes, to be read from the backend before the
200 data is sent to the client. The default of zero causes all data read of
201 any size to be passed downstream to the client immediately as it arrives.
202 Setting this to a higher value causes the disk cache to buffer at least
203 this amount before sending the result to the client. This can improve
204 performance when caching content from a reverse proxy.</p>
206 <p>This directive only takes effect when the data is being saved to the
207 cache, as opposed to data being served from the cache.</p>
209 <pre class="prettyprint lang-config">
215 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
216 <div class="directive-section"><h2><a name="CacheReadTime" id="CacheReadTime">CacheReadTime</a> <a name="cachereadtime" id="cachereadtime">Directive</a></h2>
217 <table class="directive">
218 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum time (in milliseconds) that should elapse while reading
219 before data is sent downstream</td></tr>
220 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadTime <var>milliseconds</var></code></td></tr>
221 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadTime 0</code></td></tr>
222 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
223 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
224 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
226 <p>The <code class="directive">CacheReadTime</code> directive sets the minimum amount
227 of elapsed time that should pass before making an attempt to send data
228 downstream to the client. During the time period, data will be buffered
229 before sending the result to the client. This can improve performance when
230 caching content from a reverse proxy.</p>
232 <p>The default of zero disables this option.</p>
234 <p>This directive only takes effect when the data is being saved to the
235 cache, as opposed to data being served from the cache. It is recommended
236 that this option be used alongside the
237 <code class="directive"><a href="#cachereadsize">CacheReadSize</a></code> directive to
238 ensure that the server does not buffer excessively should data arrive faster
241 <pre class="prettyprint lang-config">
247 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
248 <div class="directive-section"><h2><a name="CacheRoot" id="CacheRoot">CacheRoot</a> <a name="cacheroot" id="cacheroot">Directive</a></h2>
249 <table class="directive">
250 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The directory root under which cache files are
252 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheRoot <var>directory</var></code></td></tr>
253 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
254 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
255 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
257 <p>The <code class="directive">CacheRoot</code> directive defines the name of
258 the directory on the disk to contain cache files. If the <code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> module has been loaded or compiled in to the
259 Apache server, this directive <em>must</em> be defined. Failing to
260 provide a value for <code class="directive">CacheRoot</code> will result in
261 a configuration file processing error. The <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code> and <code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> directives define
262 the structure of the directories under the specified root directory.</p>
264 <pre class="prettyprint lang-config">
265 CacheRoot c:/cacheroot
271 <div class="bottomlang">
272 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English"> en </a> |
273 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
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275 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
276 </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>
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