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   8 <title>mod_mem_cache - Apache HTTP Server</title>
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  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_mem_cache</h1>
  23 <div class="toplang">
  24 <p><span>Available Languages: </span><a href="../en/mod/mod_mem_cache.html" title="English">&nbsp;en&nbsp;</a> |
  25 <a href="../ja/mod/mod_mem_cache.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  26 <a href="../ko/mod/mod_mem_cache.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
  27 </div>
  28 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Content cache keyed to URIs</td></tr>
  29 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  30 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>mem_cache_module</td></tr>
  31 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_mem_cache.c</td></tr></table>
  32 <h3>Summary</h3>
  33
  34     <p>This module <em>requires</em> the service of <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>. It acts as a support module for <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> and provides a memory based storage manager.
  35     <code class="module"><a href="../mod/mod_mem_cache.html">mod_mem_cache</a></code> can be configured to operate in two
  36     modes: caching open file descriptors or caching objects in heap storage.
  37     <code class="module"><a href="../mod/mod_mem_cache.html">mod_mem_cache</a></code> is most useful when used to cache locally
  38     generated content or to cache backend server content for <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> configured for <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code> (aka <dfn>reverse proxy</dfn>).</p>
  39
  40     <p>Content is stored in and retrieved from the cache using URI based
  41     keys. Content with access protection is not cached.</p>
  42 </div>
  43 <div id="quickview"><h3 class="directives">Directives</h3>
  44 <ul id="toc">
  45 <li><img alt="" src="../images/down.gif" /> <a href="#mcachemaxobjectcount">MCacheMaxObjectCount</a></li>
  46 <li><img alt="" src="../images/down.gif" /> <a href="#mcachemaxobjectsize">MCacheMaxObjectSize</a></li>
  47 <li><img alt="" src="../images/down.gif" /> <a href="#mcachemaxstreamingbuffer">MCacheMaxStreamingBuffer</a></li>
  48 <li><img alt="" src="../images/down.gif" /> <a href="#mcacheminobjectsize">MCacheMinObjectSize</a></li>
  49 <li><img alt="" src="../images/down.gif" /> <a href="#mcacheremovalalgorithm">MCacheRemovalAlgorithm</a></li>
  50 <li><img alt="" src="../images/down.gif" /> <a href="#mcachesize">MCacheSize</a></li>
  51 </ul>
  52 <h3>See also</h3>
  53 <ul class="seealso">
  54 <li><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code></li>
  55 <li><code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code></li>
  56 </ul></div>
  57
  58 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  59 <div class="directive-section"><h2><a name="MCacheMaxObjectCount" id="MCacheMaxObjectCount">MCacheMaxObjectCount</a> <a name="mcachemaxobjectcount" id="mcachemaxobjectcount">Directive</a></h2>
  60 <table class="directive">
  61 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum number of objects allowed to be placed in the
  62 cache</td></tr>
  63 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMaxObjectCount <var>value</var></code></td></tr>
  64 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMaxObjectCount 1009</code></td></tr>
  65 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  66 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  67 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
  68 </table>
  69     <p>The <code class="directive">MCacheMaxObjectCount</code> directive sets the
  70     maximum number of objects to be cached. The value is used to create the
  71     open hash table. If a new object needs to be inserted in the cache and
  72     the maximum number of objects has been reached, an object will be
  73     removed to allow the new object to be cached. The object to be removed
  74     is selected using the algorithm specified by <code class="directive"><a href="#mcacheremovalalgorithm">MCacheRemovalAlgorithm</a></code>.</p>
  75
  76     <div class="example"><h3>Example</h3><p><code>
  77       MCacheMaxObjectCount 13001
  78     </code></p></div>
  79
  80 </div>
  81 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  82 <div class="directive-section"><h2><a name="MCacheMaxObjectSize" id="MCacheMaxObjectSize">MCacheMaxObjectSize</a> <a name="mcachemaxobjectsize" id="mcachemaxobjectsize">Directive</a></h2>
  83 <table class="directive">
  84 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum size (in bytes) of a document allowed in the
  85 cache</td></tr>
  86 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMaxObjectSize <var>bytes</var></code></td></tr>
  87 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMaxObjectSize 10000</code></td></tr>
  88 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  89 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  90 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
  91 </table>
  92     <p>The <code class="directive">MCacheMaxObjectSize</code> directive sets the
  93     maximum allowable size, in bytes, of a document for it to be considered
  94     cacheable.</p>
  95
  96     <div class="example"><h3>Example</h3><p><code>
  97       MCacheMaxObjectSize 6400000
  98     </code></p></div>
  99
 100     <div class="note"><h3>Note</h3>
 101       <p>The value of <code class="directive">MCacheMaxObjectSize</code> must be
 102       greater than the value specified by the <code class="directive"><a href="#mcacheminobjectsize">MCacheMinObjectSize</a></code> directive.</p>
 103     </div>
 104
 105 </div>
 106 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 107 <div class="directive-section"><h2><a name="MCacheMaxStreamingBuffer" id="MCacheMaxStreamingBuffer">MCacheMaxStreamingBuffer</a> <a name="mcachemaxstreamingbuffer" id="mcachemaxstreamingbuffer">Directive</a></h2>
 108 <table class="directive">
 109 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of a streamed response to buffer in memory
 110 before declaring the response uncacheable</td></tr>
 111 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMaxStreamingBuffer <var>size_in_bytes</var></code></td></tr>
 112 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMaxStreamingBuffer the smaller of 100000 or MCacheMaxObjectSize</code></td></tr>
 113 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 114 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 115 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
 116 </table>
 117     <p>The <code class="directive">MCacheMaxStreamingBuffer</code> directive
 118     specifies the maximum number of bytes of a streamed response to
 119     buffer before deciding that the response is too big to cache.
 120     A streamed response is one in which the entire content is not
 121     immediately available and in which the <code>Content-Length</code>
 122     may not be known. Sources of streaming responses include proxied
 123     responses and the output of CGI scripts. By default, a streamed
 124     response will <em>not</em> be cached unless it has a
 125     <code>Content-Length</code> header. The reason for this is to
 126     avoid using a large amount of memory to buffer a partial response
 127     that might end up being too large to fit in the cache.
 128     The <code class="directive">MCacheMaxStreamingBuffer</code> directive allows
 129     buffering of streamed responses that don't contain a
 130     <code>Content-Length</code> up to the specified maximum amount of
 131     space. If the maximum buffer space is reached, the buffered
 132     content is discarded and the attempt to cache is abandoned.</p>
 133
 134     <div class="note"><h3>Note:</h3>
 135       <p>Using a nonzero value for <code class="directive">MCacheMaxStreamingBuffer</code>
 136       will not delay the transmission of the response to the client.
 137       As soon as <code class="module"><a href="../mod/mod_mem_cache.html">mod_mem_cache</a></code> copies a block of streamed
 138       content into a buffer, it sends the block on to the next output
 139       filter for delivery to the client.</p>
 140     </div>
 141
 142     <div class="example"><p><code>
 143       # Enable caching of streamed responses up to 64KB:<br />
 144       MCacheMaxStreamingBuffer 65536
 145     </code></p></div>
 146
 147 </div>
 148 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 149 <div class="directive-section"><h2><a name="MCacheMinObjectSize" id="MCacheMinObjectSize">MCacheMinObjectSize</a> <a name="mcacheminobjectsize" id="mcacheminobjectsize">Directive</a></h2>
 150 <table class="directive">
 151 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of a document to be allowed in the
 152 cache</td></tr>
 153 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheMinObjectSize <var>bytes</var></code></td></tr>
 154 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheMinObjectSize 0</code></td></tr>
 155 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 156 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 157 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
 158 </table>
 159     <p>The <code class="directive">MCacheMinObjectSize</code> directive sets the
 160     minimum size in bytes of a document for it to be considered
 161     cacheable.</p>
 162
 163     <div class="example"><h3>Example</h3><p><code>
 164       MCacheMinObjectSize 10000
 165     </code></p></div>
 166
 167 </div>
 168 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 169 <div class="directive-section"><h2><a name="MCacheRemovalAlgorithm" id="MCacheRemovalAlgorithm">MCacheRemovalAlgorithm</a> <a name="mcacheremovalalgorithm" id="mcacheremovalalgorithm">Directive</a></h2>
 170 <table class="directive">
 171 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The algorithm used to select documents for removal from the
 172 cache</td></tr>
 173 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheRemovalAlgorithm LRU|GDSF</code></td></tr>
 174 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheRemovalAlgorithm GDSF</code></td></tr>
 175 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 176 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 177 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
 178 </table>
 179     <p>The <code class="directive">MCacheRemovalAlgorithm</code> directive specifies
 180     the algorithm used to select documents for removal from the cache.
 181     Two choices are available:</p>
 182
 183     <dl>
 184       <dt><code>LRU</code> (Least Recently Used)</dt>
 185       <dd><code>LRU</code> removes the documents that have not been accessed
 186       for the longest time.</dd>
 187
 188       <dt><code>GDSF</code> (GreadyDual-Size)</dt>
 189       <dd><code>GDSF</code> assigns a priority to cached documents based
 190       on the cost of a cache miss and the size of the document. Documents
 191       with the lowest priority are removed first.</dd>
 192     </dl>
 193
 194     <div class="example"><h3>Example</h3><p><code>
 195       MCacheRemovalAlgorithm GDSF<br />
 196       MCacheRemovalAlgorithm LRU
 197     </code></p></div>
 198
 199 </div>
 200 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 201 <div class="directive-section"><h2><a name="MCacheSize" id="MCacheSize">MCacheSize</a> <a name="mcachesize" id="mcachesize">Directive</a></h2>
 202 <table class="directive">
 203 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum amount of memory used by the cache in
 204 KBytes</td></tr>
 205 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MCacheSize <var>KBytes</var></code></td></tr>
 206 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MCacheSize 100</code></td></tr>
 207 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 208 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 209 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_mem_cache</td></tr>
 210 </table>
 211     <p>The <code class="directive">MCacheSize</code> directive sets the maximum
 212     amount of memory to be used by the cache, in KBytes (1024-byte units).
 213     If a new object needs to be inserted in the cache and the size of the
 214     object is greater than the remaining memory, objects will be removed
 215     until the new object can be cached. The object to be removed is
 216     selected using the algorithm specified by <code class="directive"><a href="#mcacheremovalalgorithm">MCacheRemovalAlgorithm</a></code>.</p>
 217
 218     <div class="example"><h3>Example</h3><p><code>
 219       MCacheSize 700000
 220     </code></p></div>
 221
 222     <div class="note"><h3>Note</h3>
 223       <p>The <code class="directive">MCacheSize</code> value must be greater than
 224       the value specified by the <code class="directive"><a href="#mcachemaxobjectsize">MCacheMaxObjectSize</a></code> directive.</p>
 225     </div>
 226
 227 </div>
 228 </div>
 229 <div class="bottomlang">
 230 <p><span>Available Languages: </span><a href="../en/mod/mod_mem_cache.html" title="English">&nbsp;en&nbsp;</a> |
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 232 <a href="../ko/mod/mod_mem_cache.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
 233 </div><div id="footer">
 234 <p class="apache">Copyright 1995-2006 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
 235 <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>
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