Re: [BUG] pg_basebackup from disconnected standby fails

Hello, thank you for the comment.

At Fri, 8 Jul 2016 14:42:20 -0400, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote in <20160708184220(dot)GA733807(at)alvherre(dot)pgsql>
> Kyotaro HORIGUCHI wrote:
>
> > At Fri, 10 Jun 2016 17:39:59 +0900, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote in <CAB7nPqTv5gmKQcNDoFGTGqoqXz2xLz4RRw247oqOJzZTVy6-7Q(at)mail(dot)gmail(dot)com>
> > > On Thu, Jun 9, 2016 at 9:55 PM, Kyotaro HORIGUCHI
> > > <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>
> > > Indeed, and you could just do the following to reproduce the failure
> > > with the recovery test suite, so I would suggest adding this test in
> > > the patch:
> > > --- a/src/test/recovery/t/001_stream_rep.pl
> > > +++ b/src/test/recovery/t/001_stream_rep.pl
> > > @@ -24,6 +24,11 @@ $node_standby_1->start;
> > > # pg_basebackup works on a standby).
> > > $node_standby_1->backup($backup_name);
> > >
> > > +# Take a second backup of the standby while the master is offline.
> > > +$node_master->stop;
> > > +$node_standby_1->backup('my_backup_2');
> > > +$node_master->start;
> >
> > I'm not sure that adding the test case for a particular bug like
> > this is appropriate. But it would be acceptable because it
> > doesn't take long time and it is separate from standard checks.
>
> The reason this test is appropiate is that it's testing a feature we
> want to support, namely that taking a backup from a standby works even
> when the master is stopped. It's not a test for this particular bug,
> even though the feature doesn't work because of this bug.

That's true, but we don't always have a perfectly comprehensive
test suite, consciously or unconsciously. The sentence was
inattentive but the "bug" was just the negative comparable to
"feature" in my mind. My point was the comparison between adding
a test for a corner-case and its cost. It must be added if the
fixed feature is fragile. It can be added it doesn't take a too
long time to finish.

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center