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
       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)

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