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MEMCACHE_TABLE(5)                                                                          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 speci-
       fies 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  accessi-ble accessible
              ble by the unprivileged postfix user.

       backup (default: undefined)
              An  optional  Postfix  database that provides persistent backup for the memcache database. 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 using memcache with persistent backup as postscreen(8) or verify(8) cache, dis-able disable
              able automatic cache cleanup (*_cache_cleanup_interval = 0) in all  Postfix  instances  except
              for one instance that will be responsible for cache cleanup.

              NOTE 2: In the case of a proxied backup database, 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.

       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 in memcache requests.  By default, these are the same  as
              the lookup and update keys that are given to the Postfix memcache client.

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

              When the same memcache database is used to cache information from multiple tables, you can use
              the key_format feature to avoid name collisions by prepending a fixed string.  Examples:

                  key_format = aliases:%s
                  key_format = access:%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  suppressed  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  significant  compo-nent component
                     nent  of  the input key's domain. If the input key is user@mail.example.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 satisfy 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).  Example:

                  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 virtual_uid_maps, virtual_gid_maps and  vir-tual_mailbox_maps virtual_mailbox_maps
       tual_mailbox_maps (these specify UNIX process privileges 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-sensitive 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 MEMCACHE MAIN PARAMETERS sec-tion section
       tion 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)