Re: max_standby_delay considered harmful

On Sat, May 8, 2010 at 6:51 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> Robert Haas wrote:
>> On Sat, May 8, 2010 at 3:40 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> > Robert Haas wrote:
>> >> On Sat, May 8, 2010 at 2:48 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> >> > I think the concensus is to change this setting to a boolean. ?If you
>> >> > don't want to do it, I am sure we can find someone who will.
>> >>
>> >> I still think we should revert to Tom's original proposal.
>> >
>> > And Tom's proposal was to do it on WAL slave arrival time? ?If we could
>> > get agreement from everyone that that is the proper direction, fine, but
>> > I am hearing things like plugins, and other complexity that makes it
>> > seem we are not getting closer to an agreed solution, and without
>> > agreement, the simplest approach seems to be just to remove the part we
>> > can't agree upon.
>> >
>> > I think the big question is whether this issue is significant enough
>> > that we should ignore our policy of no feature design during beta.
>>
>> Tom's proposal was basically to define recovery_process_lock_timeout.
>> The recovery process would wait X seconds for a lock, then kill
>> whoever held it.  It's not the greatest knob in the world for the
>> reasons already pointed out, but I think it's still better than a
>> boolean and will be useful to some users.  And it's pretty simple.
>
> I thought there was concern about lock stacking causing
> unpredictable/unbounded delays.   I am not sure boolean has a majority
> vote, but I am suggesting that because it is the _minimal_ feature set,
> and when we can't agree during beta, the minimal feature set seems like
> the best choice.
>
> Clearly, anything is more feature-full than boolean --- the big question
> is whether Tom's proposal is significantly better than boolean that we
> should spend the time designing and implementing it, with the
> possibility it will all be changed in 9.1.

I doubt it's likely to be thrown out completely. We might decide to
fine-tune it in some way. My fear is that if we ship this with only a
boolean, we're shipping crippleware. If that fear turns out to be
unfounded, I will of course be happy, but that's my concern, and I
don't believe that it's entirely unfounded.

--
Robert Haas
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