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   8 <title>mod_cache_disk - Apache HTTP Server</title>
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  15 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
  16 <p class="apache">Apache HTTP Server Version 2.3</p>
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  20 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.3</a> &gt; <a href="./">Modules</a></div>
  21 <div id="page-content">
  22 <div id="preamble"><h1>Apache Module mod_cache_disk</h1>
  23 <div class="toplang">
  24 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English">&nbsp;en&nbsp;</a> |
  25 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
  26 <a href="../ja/mod/mod_cache_disk.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  27 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
  28 </div>
  29 <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>
  30 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  31 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>cache_disk_module</td></tr>
  32 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_cache_disk.c</td></tr></table>
  33 <h3>Summary</h3>
  34
  35     <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> implements a disk based storage
  36     manager for <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>.</p>
  37
  38     <p>The headers and bodies of cached responses are stored separately on
  39     disk, in a directory structure derived from the md5 hash of the cached
  40     URL.</p>
  41
  42     <p>Multiple content negotiated responses can be stored concurrently,
  43     however the caching of partial content is not yet supported by this
  44     module.</p>
  45
  46     <p>Atomic cache updates to both header and body files are achieved
  47     without the need for locking by storing the device and inode numbers of
  48     the body file within the header file. This has the side effect that
  49     cache entries manually moved into the cache will be ignored.</p>
  50
  51     <p>The <code class="program"><a href="../programs/htcacheclean.html">htcacheclean</a></code> tool is provided to list cached
  52     URLs, remove cached URLs, or to maintain the size of the disk cache
  53     within size and/or inode limits. The tool can be run on demand, or
  54     can be daemonized to offer continuous monitoring of directory sizes.</p>
  55
  56     <div class="note"><h3>Note:</h3>
  57       <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> requires the services of
  58       <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>, which must be
  59       loaded before mod_cache_disk.</p>
  60     </div>
  61     <div class="note"><h3>Note:</h3>
  62       <p><code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> uses the sendfile feature to
  63       serve files from the cache when supported by the platform, and
  64       when enabled with <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code>.
  65       However, per-directory and .htaccess configuration of
  66       <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> are ignored by
  67       <code class="module"><a href="../mod/mod_cache_disk.html">mod_cache_disk</a></code> as the corresponding settings are not
  68       available to the module when a request is being served from the
  69       cache.</p>
  70     </div>
  71 </div>
  72 <div id="quickview"><h3 class="directives">Directives</h3>
  73 <ul id="toc">
  74 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlength">CacheDirLength</a></li>
  75 <li><img alt="" src="../images/down.gif" /> <a href="#cachedirlevels">CacheDirLevels</a></li>
  76 <li><img alt="" src="../images/down.gif" /> <a href="#cachemaxfilesize">CacheMaxFileSize</a></li>
  77 <li><img alt="" src="../images/down.gif" /> <a href="#cacheminfilesize">CacheMinFileSize</a></li>
  78 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadsize">CacheReadSize</a></li>
  79 <li><img alt="" src="../images/down.gif" /> <a href="#cachereadtime">CacheReadTime</a></li>
  80 <li><img alt="" src="../images/down.gif" /> <a href="#cacheroot">CacheRoot</a></li>
  81 </ul>
  82 </div>
  83
  84 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  85 <div class="directive-section"><h2><a name="CacheDirLength" id="CacheDirLength">CacheDirLength</a> <a name="cachedirlength" id="cachedirlength">Directive</a></h2>
  86 <table class="directive">
  87 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of characters in subdirectory names</td></tr>
  88 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLength <var>length</var></code></td></tr>
  89 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLength 2</code></td></tr>
  90 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
  91 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  92 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
  93 </table>
  94     <p>The <code class="directive">CacheDirLength</code> directive sets the number
  95     of characters for each subdirectory name in the cache hierarchy. It can
  96     be used in conjunction with <code class="directive">CacheDirLevels</code> to
  97     determine the approximate structure of your cache hierarchy.</p>
  98     <p>A high value for <code class="directive">CacheDirLength</code> combined
  99     with a low value for <code class="directive">CacheDirLevels</code> will result in
 100     a relatively flat hierarchy, with a large number of subdirectories at each
 101     level.</p>
 102
 103     <div class="note">
 104       <p>The result of <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code>* <code class="directive">CacheDirLength</code>
 105       must not be higher than 20.</p>
 106     </div>
 107
 108
 109 </div>
 110 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 111 <div class="directive-section"><h2><a name="CacheDirLevels" id="CacheDirLevels">CacheDirLevels</a> <a name="cachedirlevels" id="cachedirlevels">Directive</a></h2>
 112 <table class="directive">
 113 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of levels of subdirectories in the
 114 cache.</td></tr>
 115 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLevels <var>levels</var></code></td></tr>
 116 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLevels 2</code></td></tr>
 117 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 118 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 119 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 120 </table>
 121     <p>The <code class="directive">CacheDirLevels</code> directive sets the number
 122     of subdirectory levels in the cache. Cached data will be saved this
 123     many directory levels below the <code class="directive"><a href="#cacheroot">CacheRoot</a></code> directory.</p>
 124     <p>A high value for <code class="directive">CacheDirLevels</code> combined
 125     with a low value for <code class="directive">CacheDirLength</code> will result in
 126     a relatively deep hierarchy, with a small number of subdirectories at each
 127     level.</p>
 128
 129     <div class="note">
 130       <p>The result of <code class="directive">CacheDirLevels</code>*
 131       <code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> must
 132       not be higher than 20.</p>
 133     </div>
 134
 135
 136 </div>
 137 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 138 <div class="directive-section"><h2><a name="CacheMaxFileSize" id="CacheMaxFileSize">CacheMaxFileSize</a> <a name="cachemaxfilesize" id="cachemaxfilesize">Directive</a></h2>
 139 <table class="directive">
 140 <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
 141 cache</td></tr>
 142 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMaxFileSize <var>bytes</var></code></td></tr>
 143 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMaxFileSize 1000000</code></td></tr>
 144 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 145 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 146 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 147 </table>
 148     <p>The <code class="directive">CacheMaxFileSize</code> directive sets the
 149     maximum size, in bytes, for a document to be considered for storage in
 150     the cache.</p>
 151
 152     <div class="example"><p><code>
 153       CacheMaxFileSize 64000
 154     </code></p></div>
 155
 156 </div>
 157 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 158 <div class="directive-section"><h2><a name="CacheMinFileSize" id="CacheMinFileSize">CacheMinFileSize</a> <a name="cacheminfilesize" id="cacheminfilesize">Directive</a></h2>
 159 <table class="directive">
 160 <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
 161 cache</td></tr>
 162 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMinFileSize <var>bytes</var></code></td></tr>
 163 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMinFileSize 1</code></td></tr>
 164 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 165 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 166 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 167 </table>
 168     <p>The <code class="directive">CacheMinFileSize</code> directive sets the
 169     minimum size, in bytes, for a document to be considered for storage
 170     in the cache.</p>
 171
 172     <div class="example"><p><code>
 173       CacheMinFileSize 64
 174     </code></p></div>
 175
 176 </div>
 177 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 178 <div class="directive-section"><h2><a name="CacheReadSize" id="CacheReadSize">CacheReadSize</a> <a name="cachereadsize" id="cachereadsize">Directive</a></h2>
 179 <table class="directive">
 180 <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
 181   before sending the data downstream</td></tr>
 182 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadSize <var>bytes</var></code></td></tr>
 183 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadSize 0</code></td></tr>
 184 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 185 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 186 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 187 </table>
 188     <p>The <code class="directive">CacheReadSize</code> directive sets the
 189     minimum amount of data, in bytes, to be read from the backend before the
 190     data is sent to the client. The default of zero causes all data read of
 191     any size to be passed downstream to the client immediately as it arrives.
 192     Setting this to a higher value causes the disk cache to buffer at least
 193     this amount before sending the result to the client. This can improve
 194     performance when caching content from a reverse proxy.</p>
 195
 196     <p>This directive only takes effect when the data is being saved to the
 197     cache, as opposed to data being served from the cache.</p>
 198
 199     <div class="example"><p><code>
 200       CacheReadSize 102400
 201     </code></p></div>
 202
 203 </div>
 204 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 205 <div class="directive-section"><h2><a name="CacheReadTime" id="CacheReadTime">CacheReadTime</a> <a name="cachereadtime" id="cachereadtime">Directive</a></h2>
 206 <table class="directive">
 207 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum time (in milliseconds) that should elapse while reading
 208   before data is sent downstream</td></tr>
 209 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadTime <var>milliseconds</var></code></td></tr>
 210 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadTime 0</code></td></tr>
 211 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 212 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 213 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 214 </table>
 215     <p>The <code class="directive">CacheReadTime</code> directive sets the minimum amount
 216     of elapsed time that should pass before making an attempt to send data
 217     downstream to the client. During the time period, data will be buffered
 218     before sending the result to the client. This can improve performance when
 219     caching content from a reverse proxy.</p>
 220
 221     <p>The default of zero disables this option.</p>
 222
 223     <p>This directive only takes effect when the data is being saved to the
 224     cache, as opposed to data being served from the cache. It is recommended
 225     that this option be used alongside the
 226     <code class="directive"><a href="#cachereadsize">CacheReadSize</a></code> directive to
 227     ensure that the server does not buffer excessively should data arrive faster
 228     than expected.</p>
 229
 230     <div class="example"><p><code>
 231       CacheReadTime 1000
 232     </code></p></div>
 233
 234 </div>
 235 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 236 <div class="directive-section"><h2><a name="CacheRoot" id="CacheRoot">CacheRoot</a> <a name="cacheroot" id="cacheroot">Directive</a></h2>
 237 <table class="directive">
 238 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The directory root under which cache files are
 239 stored</td></tr>
 240 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheRoot <var>directory</var></code></td></tr>
 241 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 242 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 243 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache_disk</td></tr>
 244 </table>
 245     <p>The <code class="directive">CacheRoot</code> directive defines the name of
 246     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
 247     Apache server, this directive <em>must</em> be defined. Failing to
 248     provide a value for <code class="directive">CacheRoot</code> will result in
 249     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
 250     the structure of the directories under the specified root directory.</p>
 251
 252     <div class="example"><p><code>
 253       CacheRoot c:/cacheroot
 254     </code></p></div>
 255
 256 </div>
 257 </div>
 258 <div class="bottomlang">
 259 <p><span>Available Languages: </span><a href="../en/mod/mod_cache_disk.html" title="English">&nbsp;en&nbsp;</a> |
 260 <a href="../fr/mod/mod_cache_disk.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
 261 <a href="../ja/mod/mod_cache_disk.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
 262 <a href="../ko/mod/mod_cache_disk.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
 263 </div><div id="footer">
 264 <p class="apache">Copyright 2011 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>
 265 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
 266 </body></html>