    FLUSH(8)                                                              FLUSH(8)

    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 per-
           formance of the SMTP ETRN request, and of its command-line
           equivalent, "sendmail -qR" or "postqueue -f".   This  pro-
           gram 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 deferred 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  des-
           tinations is specified with the fast_flush_domains config-
           uration parameter, 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 sitename
                  Request delivery of mail that  is  queued  for  the
                  specified destination.

           refresh
                  Refresh  non-empty  per-destination  logfiles  that
                  were not read in $fast_flush_refresh_time hours, by
                  simulating send requests (see above) for the corre-
                  sponding destinations.

                  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 privi-
           lege.

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

    BUGS
           Fast flush logfiles are  truncated  only  after  a  "send"
           request,  not  when mail is actually delivered, and there-
           fore can accumulate outdated or redundant data.  In  order
           to  maintain  sanity,  "refresh" must be executed periodi-
           cally. 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 relay_domains des-
           tination 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  terminated  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 the next  service  request
                  before exiting.

           max_use (100)
                  The  maximal number of connection requests before a
                  Postfix daemon process terminates.

           parent_domain_matches_subdomains (see 'postconf  -d'  out-
           put)
                  What   Postfix   features   match   subdomains   of
                  "domain.tld" automatically, instead of requiring an
                  explicit ".domain.tld" 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  direc-
                  tory.

           syslog_facility (mail)
                  The syslog facility of Postfix logging.

           syslog_name (postfix)
                  The  mail  system  name  that  is  prepended to the
                  process name in syslog  records,  so  that  "smtpd"
                  becomes, for example, "postfix/smtpd".

    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
           syslogd(8), system logging

    README FILES
           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

                                                                          FLUSH(8)