MEMCACHE_TABLE(5)MEMCACHE_TABLE(5)NAMEmemcache_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 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 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 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. 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 ALSOpostmap(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)
