DOKK / manpages / debian 12 / postfix / memcache_table.5.en
MEMCACHE_TABLE(5) File Formats Manual MEMCACHE_TABLE(5)

memcache_table - Postfix memcache client configuration

postmap -q "string" memcache:/etc/postfix/filename
postmap -q - memcache:/etc/postfix/filename <inputfile


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.




  

  
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.

  

  

  
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 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).

  

  

  
Optional flags that should be stored along with a memcache update. The
      flags are ignored when looking up information.

  

  
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.

  













  

  
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. 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).







  

  
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

  













  

  
The maximal memcache reply data length in bytes.

  

  
The maximal memcache reply line length in bytes.

  

  
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.

  

  
The time in seconds before retrying a failed memcache command.

  

  
The time limit for sending a memcache command and for receiving a memcache
      reply.












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.








postmap(1), Postfix lookup table manager
postconf(5), configuration parameters










Use "postconf readme_directory" or
    "postconf html_directory" to locate this information.


DATABASE_README, Postfix lookup table overview
MEMCACHE_README, Postfix memcache client guide










The Secure Mailer license must be distributed with this
  software.












Memcache support was introduced with Postfix version 2.9.








Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA