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 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)