    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 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 deferred mail. A logfile is append-only, and is  trun-
           cated  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 eli-
           gible destinations. The list of eligible destinations is specified with
           the  fast_flush_domains  configuration  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_site sitename
                  Request delivery of mail that is queued for the specified desti-
                  nation.

           send_file queueid
                  Request delivery of the specified deferred message.

           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 corresponding 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 privilege.

    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 therefore can  accumulate  outdated  or
           redundant data. In order to maintain sanity, "refresh" must be executed
           periodically. This can be automated with a suitable wakeup  timer  set-
           ting 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
           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 con-
                  figuration 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-destina-
                  tion 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" log-
                  file 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 example, "smtpd" becomes "prefix/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

           Wietse Venema
           Google, Inc.
           111 8th Avenue
           New York, NY 10011, USA

                                                                          FLUSH(8)