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)