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<html><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Persistant Storage</title><link href="modsecurity-reference.css" rel="stylesheet" type="text/css"><meta content="DocBook XSL Stylesheets V1.69.1" name="generator"><link rel="start" href="index.html" title="ModSecurity® Reference
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Manual"><link rel="up" href="index.html" title="ModSecurity® Reference
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Manual"><link rel="prev" href="ar01s10.html" title="Macro Expansion"><link rel="next" href="ar01s12.html" title="Data Formats"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div style="background:#F5F5F5;width:100%;border-top:1px solid #DDDDDD;border-bottom:1px solid #DDDDDD"><table width="100%" cellspacing="0" cellpadding="0"><tr><td><a href="http://www.modsecurity.org"><img style="margin:4px" src="modsecurity.gif" width="120" height="36" alt="ModSecurity" border="0"></a></td><td align="right"><a href="http://www.breach.com"><img style="margin:6px" src="breach-logo-small.gif" height="36" width="100" border="0"></a></td></tr></table></div><div id="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">Persistant Storage</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="ar01s10.html">Prev</a> </td><td align="center" width="60%"> <a accesskey="h" href="index.html">Home</a></td><td align="right" width="20%"> <a accesskey="n" href="ar01s12.html">Next</a></td></tr></table><hr size="1"></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="N11A88"></a>Persistant Storage</h2></div></div><div></div></div><p>At this time it is only possible to have three collections in which
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data is stored persistantly (i.e. data available to multiple requests).
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These are: <code class="literal">IP</code>, <code class="literal"> SESSION</code> and <code class="literal">USER</code>.</p><p>Every collection contains several built-in variables that are
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available and are read-only unless otherwise specified:</p><div class="orderedlist"><ol type="1"><li><p><code class="literal">CREATE_TIME</code> - date/time of
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the creation of the collection.</p></li><li><p><code class="literal">IS_NEW</code> - set to 1 if the
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collection is new (not yet persisted) otherwise set to 0.</p></li><li><p><code class="literal">KEY</code> - the value of the
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initcol variable (the client's IP address in the example).</p></li><li><p><code class="literal">LAST_UPDATE_TIME</code> - date/time
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of the last update to the collection.</p></li><li><p><code class="literal">TIMEOUT</code> - date/time in
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seconds when the collection will be updated on disk from memory (if no
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other updates occur). This variable may be set if you wish to specifiy
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an explicit expiration time (default is 3600 seconds).</p></li><li><p><code class="literal">UPDATE_COUNTER</code> - how many
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times the collection has been updated since creation.</p></li><li><p><code class="literal">UPDATE_RATE</code> - is the average
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rate updates per minute since creation.</p></li></ol></div><p>To create a collection to hold session variables (<code class="literal">SESSION</code>) use action <code class="literal">setsid</code>. To create a collection to hold user
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variables (<code class="literal">USER</code>) use action <code class="literal">setuid</code>. To create a collection to hold client
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address variables (<code class="literal">IP</code>) use action
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<code class="literal">initcol</code>.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Please note that ModSecurity does not implement atomic updates of
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persistent variables at this time. Variables are read from storage
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whenever <code class="literal">initcol</code> is encountered in the rules and
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persisted at the end of request processing. On busy servers requests
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often run in parallel, leading to situations where one request
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overwrites the changes made by another request. We anticipate
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implementing atomic updates of counter values in a future
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version.</p></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>ModSecurity uses a Berkley Database (SDBM) for persistant storage.
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This type of database is generally limited to storing a maximum of 1008
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bytes per key. This may be a limitation if you are attempting to store a
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considerable amount of data in variables for a single key. Some of this
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limitation is planned to be reduced in a future version of
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ModSecurity.</p></div></div><div id="navfooter"><hr size="1"><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="ar01s10.html">Prev</a> </td><td align="center" width="20%"> </td><td align="right" width="40%"> <a accesskey="n" href="ar01s12.html">Next</a></td></tr><tr><td valign="top" align="left" width="40%">Macro Expansion </td><td align="center" width="20%"><a accesskey="h" href="index.html">Home</a></td><td valign="top" align="right" width="40%"> Data Formats</td></tr></table></div><div align="center" class="copyright">Copyright (C) 2004-2008 <a href="http://www.breach.com">Breach Security</a></div></body></html>
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