man > memcache_table(5)

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 ta‐
       bles 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) op‐
       erations. 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 num‐
              ber.  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 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  ig‐
              nored 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 per‐
              sistent backup, specify a zero *_cache_cleanup_interval value  with  all  Postfix  in‐
              stances  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 re‐
                     turns no results (an update is skipped with a warning).

              %[SUD] The upper-case equivalents of the above expansions behave in the key_format pa‐
                     rameter 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 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 satisfy  all  the  specified  pat‐
                     terns,  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 quali‐
              fied 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,  vir‐
       tual_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

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