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 prox-
ymap(8) server, the socket must be accessible by
the unprivileged postfix user.
backup (default: undefined)
An optional Postfix database that provides persis-
tent 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 develop-
ment.
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 mem-
cache database, each table should use the key_for-
mat 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 mem-
cache, and specify the largest postscreen(8) *_ttl
value or verify(8) *_expire_time value as the mem-
cache table's ttl value.
NOTE 2: According to memcache protocol documenta-
tion, a value greater than 30 days (2592000 sec-
onds) 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 Post-
fix memcache client.
NOTE 1: The key_format feature is not used for
backup database requests.
NOTE 2: When different tables share the same mem-
cache database, each table should prepend its own
unique string to the lookup key. Otherwise, auto-
matic 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. Other-
wise, %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 warn-
ing).
%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 parame-
ter 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 speci-
fied patterns, a lookup is silently sup-
pressed 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 speci-
fied, 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 mem-
cache 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 vir-
tual_uid_maps, virtual_gid_maps and virtual_mailbox_maps
(these specify UNIX process privileges or "/file/name"
destinations). In a typical deployment a memcache data-
base is writable by any process that can talk to the mem-
cache server; in contrast, security-sensitive tables must
never be writable by the unprivileged Postfix user.
The Postfix memcache client requires additional configura-
tion 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
MEMCACHE_TABLE(5)