Re: Allow interrupts on waiting standby

On Fri, Jan 27, 2017 at 10:35 AM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Fri, Jan 27, 2017 at 4:36 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> On 26 January 2017 at 19:20, Andres Freund <andres(at)anarazel(dot)de> wrote:
>>> On 2017-01-26 12:24:44 -0500, Robert Haas wrote:
>>>> On Thu, Jan 26, 2017 at 7:18 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>>>> > Currently a waiting standby doesn't allow interrupts.
>>>> >
>>>> > Patch implements that.
>>>> >
>>>> > Barring objection, patching today with backpatches.
>>>>
>>>> "today" is a little quick, but the patch looks fine. I doubt anyone's
>>>> going to screech too loud about adding a CHECK_FOR_INTERRUPTS() call.
>>>
>>> I don't quite get asking for agreement, and then not waiting as
>>> suggested. I'm personally fine with going with a CHECK_FOR_INTERRUPTS
>>> for now, but I think it'd better to replace it with a latch.
>>
>> I have waited, so not sure what you mean. Tomorrow is too late.
>
> This gives really little time for any feedback :(
>
>> Replacing with a latch wouldn't be backpatchable, IMHO.
>> I've no problem if you want to work on a deeper fix for future versions.
>
> A deeper fix for HEAD proves to not be that complicated. Please see
> the attached. The other two calls of pg_usleep() in standby.c are
> waiting with 5ms and 10ms, it is not worth switching them to a latch.

Two things I forgot in this patch:
- documentation for the new wait event
- the string for the wait event or this would show up as "???" in
pg_stat_activity.
There are no default clauses in the pgstat_get_wait_* routines so my
compiler is actually complaining...
--
Michael