Provided by: postfix_3.1.0-3_amd64 bug

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
              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  sharing  a  persistent  postscreen(8)  or  verify(8)  cache,  disable
              automatic  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
                     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  component  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  virtual_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 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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

                                                                                MEMCACHE_TABLE(5)