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Remove wal_sender_delay GUC, because it's no longer useful.

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The latch infrastructure is now capable of detecting all cases where the
walsender loop needs to wake up, so there is no reason to have an arbitrary
timeout.

Also, modify the walsender loop logic to follow the standard pattern of
ResetLatch, test for work to do, WaitLatch.  The previous coding was both
hard to follow and buggy: it would sometimes busy-loop despite having
nothing available to do, eg between receipt of a signal and the next time
it was caught up with new WAL, and it also had interesting choices like
deciding to update to WALSNDSTATE_STREAMING on the strength of information
known to be obsolete.
This commit is contained in:
Tom Lane
2011-08-10 18:50:28 -04:00
parent 79b2ee20c8
commit cff75130b5
5 changed files with 74 additions and 108 deletions
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23
doc/src/sgml/config.sgml
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@ -2008,29 +2008,6 @@ SET ENABLE_SEQSCAN TO OFF;
</para>
</listitem>
</varlistentry>
<varlistentry id="guc-wal-sender-delay" xreflabel="wal_sender_delay">
<term><varname>wal_sender_delay</varname> (<type>integer</type>)</term>
<indexterm>
<primary><varname>wal_sender_delay</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
Specifies the delay between activity rounds for WAL sender processes.
In each round the WAL sender sends any WAL accumulated since the last
round to the standby server. It then sleeps for
<varname>wal_sender_delay</> milliseconds, and repeats. The sleep
is interrupted by transaction commit, so the effects of a committed
transaction are sent to standby servers as soon as the commit
happens, regardless of this setting. The default value is one second
(<literal>1s</>).
Note that on many systems, the effective resolution of sleep delays is
10 milliseconds; setting <varname>wal_sender_delay</> to a value that
is not a multiple of 10 might have the same results as setting it to
the next higher multiple of 10. This parameter can only be set in the
<filename>postgresql.conf</> file or on the server command line.
</para>
</listitem>
</varlistentry>
<varlistentry id="guc-wal-keep-segments" xreflabel="wal_keep_segments">
<term><varname>wal_keep_segments</varname> (<type>integer</type>)</term>