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     17 <h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix memcache client Howto</h1>
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     21 <h2>Introduction</h2>
     22 
     23 <p>The Postfix memcache client allows you to hook up Postfix to a
     24 memcache server. The current implementation supports one memcache
     25 server per Postfix table, with one optional Postfix database that
     26 provides persistent backup.  The Postfix memcache client supports
     27 the lookup, update, delete and sequence operations.  The sequence
     28 (i.e. first/next) operation requires a backup database that supports
     29 this operation. </p>
     30 
     31 <p> Typically, the Postfix memcache client is used to reduce query
     32 load on a persistent database, but it may also be used to query a
     33 memory-only database for low-value, easy-to-recreate, information
     34 such as a reputation cache for postscreen(8), verify(8) or greylisting.
     35 </p>
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     37 <h2>Limitations</h2>
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     39 <ul>
     40 
     41 <li> <p> The Postfix memcache client cannot be used for security-sensitive
     42 tables such as <tt>alias_maps</tt> (these may contain "<tt>|command</tt>"
     43 and "<tt>/file/name</tt>" destinations), or <tt>virtual_uid_maps</tt>,
     44 <tt>virtual_gid_maps</tt> and <tt>virtual_mailbox_maps</tt> (these
     45 specify UNIX process privileges or "<tt>/file/name</tt>" destinations).
     46 Typically, a memcache database is writable by any process that can
     47 talk to the memcache server; in contrast, security-sensitive tables
     48 must never be writable by the unprivileged Postfix user.  </p>
     49 
     50 <li> <p> The Postfix memcache client requires additional configuration
     51 when used as postscreen(8) or verify(8) cache.  For details see the
     52 <tt>backup</tt> and <tt>ttl</tt> parameter discussions in the
     53 memcache_table(5) manual page. </p>
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     55 </ul>
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     57 <h2>Building Postfix with memcache support</h2>
     58 
     59 <p>The Postfix memcache client has no external dependencies,
     60 and is therefore built into Postfix by default. </p>
     61 
     62 <h2>Configuring memcache lookup tables</h2>
     63 
     64 <p> Configuration is described in the memcache_table(5) manpage. </p>
     65 
     66 <h2>Credits</h2>
     67 
     68 <p> The first memcache client for Postfix was written by Omar Kilani,
     69 and was based on the libmemcache library. </p>
     70 
     71 <p> Wietse wrote the current memcache client from the ground up for
     72 Postfix version 2.9.  This implementation does not use libmemcache,
     73 and bears no resemblance to earlier work.  </p>
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