Re: Timeout control within tests

On Fri, Feb 18, 2022 at 10:26:52AM -0500, Tom Lane wrote:
> Noah Misch <noah@leadboat.com> writes:
> > On Thu, Feb 17, 2022 at 09:48:25PM -0800, Andres Freund wrote:
> >> Meson's test runner has the concept of a "timeout multiplier" for ways of
> >> running tests. Meson's stuff is about entire tests (i.e. one tap test), so
> >> doesn't apply here, but I wonder if we shouldn't do something similar?
> 
> > Hmmm.  It is good if the user can express an intent that continues to make
> > sense if we change the default timeout.  For the buildfarm use case, a
> > multiplier is moderately better on that axis (PG_TEST_TIMEOUT_MULTIPLIER=100
> > beats PG_TEST_TIMEOUT_DEFAULT=18000).  For the hacker use case, an absolute
> > value is substantially better on that axis (PG_TEST_TIMEOUT_DEFAULT=3 beats
> > PG_TEST_TIMEOUT_MULTIPLIER=.016666).
> 
> FWIW, I'm fairly sure that PGISOLATIONTIMEOUT=300 was selected after
> finding that smaller values didn't work reliably in the buildfarm.
> Now maybe 741d7f1 fixed that, but I wouldn't count on it.  So while I
> approve of the idea to remove PGISOLATIONTIMEOUT in favor of using this
> centralized setting, I think that we might need to have a multiplier
> there, or else we'll end up with PG_TEST_TIMEOUT_DEFAULT set to 300
> across the board.  Perhaps the latter is fine, but a multiplier seems a
> bit more flexible.

The PGISOLATIONTIMEOUT replacement was 2*timeout_default, so isolation suites
would get 2*180s=360s.  (I don't want to lower any default timeouts, but I
don't mind raising them.)  In a sense, PG_TEST_TIMEOUT_DEFAULT is a multiplier
with as many sites as possible multiplying it by 1.  The patch has multiples
at two code sites.

> On the other hand, I also support your point that an absolute setting
> is easier to think about / adjust for special uses.  So maybe we should
> just KISS and use a single absolute setting until we find a hard reason
> why that doesn't work well.