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MEMCACHE_TABLE(5)                      File Formats Manual                      MEMCACHE_TABLE(5)



NAME
       memcache_table - Postfix memcache client configuration

SYNOPSIS
       postmap -q "string" memcache:/etc/postfix/filename

       postmap -q - memcache:/etc/postfix/filename <inputfile

DESCRIPTION
       The  Postfix mail system uses optional tables for address rewriting or mail routing. These
       tables are usually in dbm or db format.

       Alternatively, lookup tables can be specified as  memcache  instances.   To  use  memcache
       lookups, define a memcache source as a lookup table in main.cf, for example:

           virtual_alias_maps = memcache:/etc/postfix/memcache-aliases.cf

       The file /etc/postfix/memcache-aliases.cf has the same format as the Postfix main.cf file,
       and specifies the parameters described below.

       The Postfix memcache client supports the lookup, update, delete and sequence  (first/next)
       operations. The sequence operation requires a backup database that supports the operation.

MEMCACHE MAIN PARAMETERS
       memcache (default: inet:localhost:11211)
              The  memcache  server  (note: singular) that Postfix will try to connect to.  For a
              TCP server specify "inet:" followed by a hostname or address, ":", and a port  name
              or  number.  Specify an IPv6 address inside "[]".  For a UNIX-domain server specify
              "unix:" followed by the socket pathname. Examples:

                  memcache = inet:memcache.example.com:11211
                  memcache = inet:127.0.0.1:11211
                  memcache = inet:[fc00:8d00:189::3]:11211
                  memcache = unix:/path/to/socket

              NOTE: to access a UNIX-domain socket with the proxymap(8) server, the  socket  must
              be accessible by the unprivileged postfix user.

       backup (default: undefined)
              An optional Postfix database that provides persistent backup for the memcache data‐
              base. The Postfix memcache client will update the  memcache  database  whenever  it
              looks  up  or  changes  information  in  the persistent database. Specify a Postfix
              "type:table" database. Examples:

                  # Non-shared postscreen cache.
                  backup = btree:/var/lib/postfix/postscreen_cache_map

                  # Shared postscreen cache for processes on the same host.
                  backup = proxy:btree:/var/lib/postfix/postscreen_cache_map

              Access to remote proxymap servers is under development.

              NOTE 1: When sharing a persistent postscreen(8) or verify(8) cache,  disable  auto‐
              matic  cache  cleanup  (set  *_cache_cleanup_interval  = 0) except with one Postfix
              instance that will be responsible for cache cleanup.

              NOTE 2: When multiple tables share the same memcache database,  each  table  should
              use  the  key_format  feature  (see  below) to prepend its own unique string to the
              lookup key.  Otherwise, automatic postscreen(8) or verify(8) cache cleanup may  not
              work.

              NOTE 3: When the backup database is accessed with "proxy:" lookups, the full backup
              database name (including the "proxy:" prefix) must be  specified  in  the  proxymap
              server's  proxy_read_maps  or  proxy_write_maps  setting  (depending on whether the
              access is read-only or read-write).

       flags (default: 0)
              Optional flags that should be stored along with a memcache update.  The  flags  are
              ignored when looking up information.

       ttl (default: 3600)
              The expiration time in seconds of memcache updates.

              NOTE  1:  When  using  a memcache table as postscreen(8) or verify(8) cache without
              persistent backup, specify a zero *_cache_cleanup_interval value with  all  Postfix
              instances  that use the memcache, and specify the largest postscreen(8) *_ttl value
              or verify(8) *_expire_time value as the memcache table's ttl value.

              NOTE 2: According to memcache protocol documentation, a value greater than 30  days
              (2592000  seconds) specifies absolute UNIX time. Smaller values are relative to the
              time of the update.

MEMCACHE KEY PARAMETERS
       key_format (default: %s)
              Format of the lookup and update keys that the Postfix memcache client sends to  the
              memcache server.  By default, these are the same as the lookup and update keys that
              the memcache client receives from Postfix applications.

              NOTE 1: The key_format feature is not used for backup database requests.

              NOTE 2: When multiple tables share the same memcache database,  each  table  should
              prepend   its   own   unique  string  to  the  lookup  key.   Otherwise,  automatic
              postscreen(8) or verify(8) cache cleanup may not work.

              Examples:

                  key_format = aliases:%s
                  key_format = verify:%s
                  key_format = postscreen:%s

              The key_format parameter supports the following '%' expansions:

              %%     This is replaced by a literal '%' character.

              %s     This is replaced by the memcache client input key.

              %u     When the input key is an address of the form user@domain, %u is replaced  by
                     the  SQL quoted local part of the address.  Otherwise, %u is replaced by the
                     entire search string.  If the localpart is empty, a lookup is silently  sup‐
                     pressed and returns no results (an update is skipped with a warning).

              %d     When  the input key is an address of the form user@domain, %d is replaced by
                     the domain part of the address.  Otherwise, a lookup is silently  suppressed
                     and returns no results (an update is skipped with a warning).

              %[SUD] The  upper-case equivalents of the above expansions behave in the key_format
                     parameter identically to their lower-case counter-parts.

              %[1-9] The patterns %1, %2, ... %9 are replaced by the corresponding most  signifi‐
                     cant   component   of   the   input  key's  domain.  If  the  input  key  is
                     user AT mail.com, then %1 is com, %2 is example and %3 is mail. If  the
                     input  key  is unqualified or does not have enough domain components to sat‐
                     isfy all the specified patterns, a lookup is silently suppressed and returns
                     no results (an update is skipped with a warning).

       domain (default: no domain list)
              This  feature  can  significantly  reduce  database server load.  Specify a list of
              domain names, paths to files, or  "type:table"  databases.   When  specified,  only
              fully  qualified search keys with a *non-empty* localpart and a matching domain are
              eligible for lookup or  update:  bare  'user'  lookups,  bare  domain  lookups  and
              "@domain" lookups are silently skipped (updates are skipped with a warning).  Exam‐
              ple:

                  domain = example.com, hash:/etc/postfix/searchdomains

MEMCACHE ERROR CONTROLS
       data_size_limit (default: 10240)
              The maximal memcache reply data length in bytes.

       line_size_limit (default: 1024)
              The maximal memcache reply line length in bytes.

       max_try (default: 2)
              The number of times to try a memcache  command  before  giving  up.   The  memcache
              client does not retry a command when the memcache server accepts no connection.

       retry_pause (default: 1)
              The time in seconds before retrying a failed memcache command.

       timeout (default: 2)
              The time limit for sending a memcache command and for receiving a memcache reply.

BUGS
       The  Postfix  memcache  client  cannot  be  used  for  security-sensitive  tables  such as
       alias_maps  (these  may  contain  "|command  and  "/file/name"  destinations),   or   vir‐
       tual_uid_maps, virtual_gid_maps and virtual_mailbox_maps (these specify UNIX process priv‐
       ileges or "/file/name" destinations).  In a typical  deployment  a  memcache  database  is
       writable by any process that can talk to the memcache server; in contrast, security-sensi‐
       tive tables must never be writable by the unprivileged Postfix user.

       The Postfix memcache client requires additional configuration when used  as  postscreen(8)
       or  verify(8) cache.  For details see the backup and ttl parameter discussions in the MEM‐
       CACHE MAIN PARAMETERS section above.

SEE ALSO
       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       DATABASE_README, Postfix lookup table overview
       MEMCACHE_README, Postfix memcache client guide

LICENSE
       The Secure Mailer license must be distributed with this software.

HISTORY
       Memcache support was introduced with Postfix version 2.9.

AUTHOR(S)
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA



                                                                                MEMCACHE_TABLE(5)


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