From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Keepalive for max_standby_delay |
Date: | 2010-06-03 16:58:45 |
Message-ID: | 6558.1275584325@sss.pgh.pa.us |
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Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Wed, 2010-06-02 at 16:00 -0400, Tom Lane wrote:
>> the current situation that query grace periods go to zero
> Possibly a better way to handle this concern is to make the second
> parameter: min_standby_grace_period - the minimum time a query will be
> given in which to execute, even if max_standby_delay has been reached or
> exceeded.
> Would that more directly address you concerns?
> min_standby_grace_period (ms) SIGHUP
A minimum grace period seems like a good idea to me, but I think it's
somewhat orthogonal to the core problem here. I think we all
intuitively feel that there should be a way to dial back the grace
period when a slave is "far behind" on applying WAL. The problem is
first how to figure out what "far behind" means, and second how to
adjust the grace period in a way that doesn't have surprising
misbehaviors. A minimum grace period would prevent some of the very
worst misbehaviors but it's not really addressing the core problem.
regards, tom lane
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