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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)