Re: Keepalive for max_standby_delay

Simon Riggs <simon@2ndQuadrant.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