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 mem‐
cache 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 different 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
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 1: The key_format feature is not used for backup database requests.
NOTE 2: When different 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 identi‐
cally 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 [email protected], 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
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)
Back to main site | Back to man page index