man > FLUSH(8postfix)

FLUSH(8postfix)                                                                      FLUSH(8postfix)

NAME
       flush - Postfix fast flush server

SYNOPSIS
       flush [generic Postfix daemon options]

DESCRIPTION
       The  flush(8) server maintains a record of deferred mail by destination.  This information is
       used to improve the performance of the SMTP ETRN request, and of its command-line equivalent,
       "sendmail -qR" or "postqueue -f".  This program expects to be run from the master(8)  process
       manager.

       The  record is implemented as a per-destination logfile with as contents the queue IDs of de‐
       ferred mail. A logfile is append-only, and is truncated when delivery is  requested  for  the
       corresponding destination. A destination is the part on the right-hand side of the right-most
       @ in an email address.

       Per-destination  logfiles of deferred mail are maintained only for eligible destinations. The
       list of eligible destinations is specified with the fast_flush_domains configuration  parame‐
       ter, which defaults to $relay_domains.

       This server implements the following requests:

       add sitename queueid
              Inform  the flush(8) server that the message with the specified queue ID is queued for
              the specified destination.

       send_site sitename
              Request delivery of mail that is queued for the specified destination.

       send_file queueid
              Request delivery of the specified deferred message.

       refresh
              Refresh non-empty per-destination logfiles  that  were  not  read  in  $fast_flush_re‐
              fresh_time hours, by simulating send requests (see above) for the corresponding desti‐
              nations.

              Delete  empty per-destination logfiles that were not updated in $fast_flush_purge_time
              days.

              This request completes in the background.

       purge  Do a refresh for all per-destination logfiles.

SECURITY
       The flush(8) server is not security-sensitive. It does not talk to the network, and  it  does
       not talk to local users.  The fast flush server can run chrooted at fixed low privilege.

DIAGNOSTICS
       Problems and transactions are logged to syslogd(8) or postlogd(8).

BUGS
       Fast  flush logfiles are truncated only after a "send" request, not when mail is actually de‐
       livered, and therefore can accumulate outdated or redundant data. In order to  maintain  san‐
       ity,  "refresh"  must  be executed periodically. This can be automated with a suitable wakeup
       timer setting in the master.cf configuration file.

       Upon receipt of a request to deliver mail for an eligible destination,  the  flush(8)  server
       requests  delivery  of all messages that are listed in that destination's logfile, regardless
       of the recipients of those messages. This is not an issue for mail that  is  sent  to  a  re‐
       lay_domains destination because such mail typically only has recipients in one domain.

CONFIGURATION PARAMETERS
       Changes  to  main.cf are picked up automatically as flush(8) processes run for only a limited
       amount of time. Use the command "postfix reload" to speed up a change.

       The text below provides only a parameter summary. See postconf(5) for more details  including
       examples.

       config_directory (see 'postconf -d' output)
              The default location of the Postfix main.cf and master.cf configuration files.

       daemon_timeout (18000s)
              How  much time a Postfix daemon process may take to handle a request before it is ter‐
              minated by a built-in watchdog timer.

       fast_flush_domains ($relay_domains)
              Optional list of destinations that are eligible for per-destination logfiles with mail
              that is queued to those destinations.

       fast_flush_refresh_time (12h)
              The time after which a non-empty but unread per-destination "fast flush" logfile needs
              to be refreshed.

       fast_flush_purge_time (7d)
              The time after which an empty per-destination "fast flush" logfile is deleted.

       ipc_timeout (3600s)
              The time limit for sending or receiving information  over  an  internal  communication
              channel.

       max_idle (100s)
              The  maximum  amount of time that an idle Postfix daemon process waits for an incoming
              connection before terminating voluntarily.

       max_use (100)
              The maximal number of incoming connections that a Postfix daemon process will  service
              before terminating voluntarily.

       parent_domain_matches_subdomains (see 'postconf -d' output)
              A  list of Postfix features where the pattern "example.com" also matches subdomains of
              example.com, instead of requiring an explicit ".example.com" pattern.

       process_id (read-only)
              The process ID of a Postfix command or daemon process.

       process_name (read-only)
              The process name of a Postfix command or daemon process.

       queue_directory (see 'postconf -d' output)
              The location of the Postfix top-level queue directory.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

       syslog_name (see 'postconf -d' output)
              A prefix that is prepended to the process name in syslog records, so that,  for  exam‐
              ple, "smtpd" becomes "prefix/smtpd".

       Available in Postfix 3.3 and later:

       service_name (read-only)
              The master.cf service name of a Postfix daemon process.

FILES
       /var/spool/postfix/flush, "fast flush" logfiles.

SEE ALSO
       smtpd(8), SMTP server
       qmgr(8), queue manager
       postconf(5), configuration parameters
       master(5), generic daemon options
       master(8), process manager
       postlogd(8), Postfix logging
       syslogd(8), system logging

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       ETRN_README, Postfix ETRN howto

LICENSE
       The Secure Mailer license must be distributed with this software.

HISTORY
       This service was introduced with Postfix version 1.0.

AUTHOR(S)
       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

                                                                                     FLUSH(8postfix)