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8 <title>mod_cache_disk - Apache HTTP Server Version 2.5</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">CacheMaxFileSize 64000</pre>
164 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
165 <div class="directive-section"><h2><a name="CacheMinFileSize" id="CacheMinFileSize">CacheMinFileSize</a> <a name="cacheminfilesize" id="cacheminfilesize">Directive</a></h2>
166 <table class="directive">
167 <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
169 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMinFileSize <var>bytes</var></code></td></tr>
170 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMinFileSize 1</code></td></tr>
171 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
172 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
173 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
175 <p>The <code class="directive">CacheMinFileSize</code> directive sets the
176 minimum size, in bytes, for a document to be considered for storage
179 <pre class="prettyprint lang-config">CacheMinFileSize 64</pre>
183 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
184 <div class="directive-section"><h2><a name="CacheReadSize" id="CacheReadSize">CacheReadSize</a> <a name="cachereadsize" id="cachereadsize">Directive</a></h2>
185 <table class="directive">
186 <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
187 before sending the data downstream</td></tr>
188 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadSize <var>bytes</var></code></td></tr>
189 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadSize 0</code></td></tr>
190 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
191 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
192 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
194 <p>The <code class="directive">CacheReadSize</code> directive sets the
195 minimum amount of data, in bytes, to be read from the backend before the
196 data is sent to the client. The default of zero causes all data read of
197 any size to be passed downstream to the client immediately as it arrives.
198 Setting this to a higher value causes the disk cache to buffer at least
199 this amount before sending the result to the client. This can improve
200 performance when caching content from a reverse proxy.</p>
202 <p>This directive only takes effect when the data is being saved to the
203 cache, as opposed to data being served from the cache.</p>
205 <pre class="prettyprint lang-config">CacheReadSize 102400</pre>
209 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
210 <div class="directive-section"><h2><a name="CacheReadTime" id="CacheReadTime">CacheReadTime</a> <a name="cachereadtime" id="cachereadtime">Directive</a></h2>
211 <table class="directive">
212 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum time (in milliseconds) that should elapse while reading
213 before data is sent downstream</td></tr>
214 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadTime <var>milliseconds</var></code></td></tr>
215 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadTime 0</code></td></tr>
216 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
217 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
218 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
220 <p>The <code class="directive">CacheReadTime</code> directive sets the minimum amount
221 of elapsed time that should pass before making an attempt to send data
222 downstream to the client. During the time period, data will be buffered
223 before sending the result to the client. This can improve performance when
224 caching content from a reverse proxy.</p>
226 <p>The default of zero disables this option.</p>
228 <p>This directive only takes effect when the data is being saved to the
229 cache, as opposed to data being served from the cache. It is recommended
230 that this option be used alongside the
231 <code class="directive"><a href="#cachereadsize">CacheReadSize</a></code> directive to
232 ensure that the server does not buffer excessively should data arrive faster
235 <pre class="prettyprint lang-config">CacheReadTime 1000</pre>
239 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
240 <div class="directive-section"><h2><a name="CacheRoot" id="CacheRoot">CacheRoot</a> <a name="cacheroot" id="cacheroot">Directive</a></h2>
241 <table class="directive">
242 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The directory root under which cache files are
244 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheRoot <var>directory</var></code></td></tr>
245 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
246 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
247 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
249 <p>The <code class="directive">CacheRoot</code> directive defines the name of
250 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
251 Apache server, this directive <em>must</em> be defined. Failing to
252 provide a value for <code class="directive">CacheRoot</code> will result in
253 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
254 the structure of the directories under the specified root directory.</p>
256 <pre class="prettyprint lang-config">CacheRoot c:/cacheroot</pre>
261 <div class="bottomlang">
262 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English"> en </a> |
263 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
264 <a href="../ja/mod/mod_cache_disk.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
265 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
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