Re: max_standby_delay considered harmful

On May 10, 2010, at 17:39 , Kevin Grittner wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> Robert Haas wrote:
>
>>> Overall I would say opinion is about evenly split between:
>>>
>>> - leave it as-is
>>> - make it a Boolean
>>> - change it in some way but to something more expressive than a
>>> Boolean
>
> I think a boolean would limit the environments in which HS would be
> useful. Personally, I think how far the replica is behind the
> source is a more useful metric, even with anomalies on the
> transition from idle to active; but a blocking duration would be
> much better than no finer control than the boolean. So my "instant
> runoff second choice" would be for the block duration knob.

You could always toggle that boolean automatically, based on some measurement of the replication lag (Assuming the boolean would be settable at runtime). That'd give you much more flexibility than any built-on knob could provide, and even more so than a built-in knob with known deficiencies.

My preference is hence to make it a boolean, but in a way that allows more advanced behavior to be implemented on top of it. In the simplest case by allowing the boolean to be flipped at runtime and ensuring that the system reacts in a sane way.

best regards,
Florian Pflug