FLUSH(8)                                                 FLUSH(8)
NAME
       flush - Postfix fast flush server
SYNOPSIS
       flush [generic Postfix daemon options]
DESCRIPTION
       The  flush  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.  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  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:
       FLUSH_REQ_ADD sitename queue_id
              Inform  the  fast  flush  server that the specified
              message is queued for sitename. Depending  on  log-
              ging  policy,  the  fast  flush  server  stores  or
              ignores the information.
       FLUSH_REQ_SEND sitename
              Request delivery of mail that is queued  for  site-
              name.   If  the  destination is eligible for a fast
              flush logfile, this request  triggers  delivery  of
              messages  listed in that destination's logfile, and
              the logfile is truncated to zero length; if mail is
              undeliverable it will be added back to the logfile.
              If the destination is not eligible for a fast flush
              logfile,  this  request  is rejected (see below for
              status codes).
       TRIGGER_REQ_WAKEUP
              This wakeup request from the master is an  alterna-
              tive way to request FLUSH_REQ_REFRESH.
       FLUSH_REQ_REFRESH (completes in the background)
              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.
       FLUSH_REQ_PURGE (completes in the background)
              Refresh  all non-empty per-destination logfiles, by
              simulating send requests (see above) for the corre-
              sponding  destinations.   This  can  be  incredibly
              expensive when logging is enabled for many destina-
              tions, and is not recommended.
              Delete empty per-destination logfiles that were not
              updated in fast_flush_purge_time days.
       The server response is one of:
       FLUSH_STAT_OK
              The request completed normally.
       FLUSH_STAT_BAD
              The flush server rejected the request (bad  request
              name, bad request parameter value).
       FLUSH_STAT_FAIL
              The request failed.
       FLUSH_STAT_DENY
              The  request  was  denied  because  the destination
              domain is not eligible for fast flush  service,  or
              because the fast flush service is disabled.
SECURITY
       The  fast  flush 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
       FLUSH_REQ_SEND  request,  not when mail is actually deliv-
       ered, and therefore can accumulate outdated  or  redundant
       data.  In order to maintain sanity, FLUSH_REQ_REFRESH must
       be executed periodically. This can  be  automated  with  a
       suitable  wakeup timer setting in the master.cf configura-
       tion file.
       Upon receipt of a request to deliver all mail for an  eli-
       gible  destination,  the flush server requests delivery of
       all messages that are listed in  that  destination's  log-
       file, 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 recipi-
       ents in one domain.
FILES
       /var/spool/postfix/flush, location of "fast flush" logfiles.
CONFIGURATION PARAMETERS
       See the Postfix main.cf file for syntax  details  and  for
       default  values.  Use  the  postfix reload command after a
       configuration change.
       fast_flush_domains
              What destinations can have a "fast flush"  logfile.
              By default, this is set to $relay_domains.
       fast_flush_refresh_time
              Refresh  a  non-empty "fast flush" logfile that was
              not read in this amount of time (default time unit:
              hours), by simulating a send request for the corre-
              sponding destination.
       fast_flush_purge_time
              Remove an empty "fast flush" logfile that  was  not
              updated  in this amount of time (default time unit:
              days).
       parent_domain_matches_subdomains
              List of Postfix features that use  domain.tld  pat-
              terns   to  match  sub.domain.tld  (as  opposed  to
              requiring .domain.tld patterns).
SEE ALSO
       smtpd(8) Postfix SMTP server
       qmgr(8) Postfix queue manager
       syslogd(8) system logging
LICENSE
       The Secure Mailer license must be  distributed  with  this
       software.
AUTHOR(S)
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA
                                                         FLUSH(8)