    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 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  post-
                  fix 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 informa-
                  tion 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 ver-
                  ify(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.  Other-
                         wise, 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 corre-
                         sponding 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_mail-
           box_maps (these specify UNIX process privileges or "/file/name"  desti-
           nations).   In  a typical deployment a memcache database is writable by
           any process that can talk to the memcache server;  in  contrast,  secu-
           rity-sensitive  tables must never be writable by the unprivileged Post-
           fix 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
           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)