Provided by: postfix_2.9.1-4_i386 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   using  memcache  with  persistent  backup  as
              postscreen(8)  or  verify(8)  cache,  disable  automatic   cache
              cleanup  (*_cache_cleanup_interval = 0) in all Postfix instances
              except for one instance  that  will  be  responsible  for  cache
              cleanup.

              NOTE  2:  In  the  case  of  a proxied backup database, 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.

       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 in memcache requests.  By
              default, these are the same as the lookup and update  keys  that
              are given to the Postfix memcache client.

              NOTE:  The  key_format  feature  is not used for backup database
              requests.

              When the same memcache database is  used  to  cache  information
              from  multiple  tables,  you  can  use the key_format feature to
              avoid name collisions by prepending a fixed string.  Examples:

                  key_format = aliases:%s
                  key_format = access:%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

                                                             MEMCACHE_TABLE(5)