Horton

Re: Replication slot stats misgivings

Masahiko Sawada <sawada.mshk@gmail.com>

View thread View on postgr.es
From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-04-21T10:08:26Z
Lists: pgsql-hackers 
On Wed, Apr 21, 2021 at 6:36 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Apr 21, 2021 at 2:46 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > On Wed, Apr 21, 2021 at 3:09 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > On Tue, Apr 20, 2021 at 7:54 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > > >
> > > >
> > > > I've attached the patch. In addition to the test Vignesh prepared, I
> > > > added one test for the message for creating a slot that checks if the
> > > > statistics are initialized after re-creating the same name slot.
> > > >
> > >
> > > I am not sure how much useful your new test is because you are testing
> > > it for slot name for which we have removed the slot file. It is not
> > > related to stat messages this patch is sending. I think we can leave
> > > that for now.
> >
> > I might be missing something but I think the test is related to the
> > message for creating a slot that initializes all counters. No? If
> > there is no that message, we will end up getting old stats if a
> > message for dropping slot gets lost (simulated by dropping slot file)
> > and the same name slot is created.
> >
>
> The test is not waiting for a new slot creation message to reach the
> stats collector. So, if the old slot data still exists in the file and
> now when we read stats via backend, then won't there exists a chance
> that old slot stats data still exists?

You're right. We should wait for the message to reach the collector.
Or should we remove that test case?

Regards,

--
Masahiko Sawada
EDB:  https://www.enterprisedb.com/

Commits

  1. Doc: Update logical decoding stats information.

  2. Fix tests for replication slots stats.

  3. Update replication statistics after every stream/spill.

  4. Fix the computation of slot stats for 'total_bytes'.

  5. Another try to fix the test case added by commit f5fc2f5b23.

  6. Use HTAB for replication slot statistics.

  7. Fix test case added by commit f5fc2f5b23.

  8. Add information of total data processed to replication slot stats.

  9. Use NameData datatype for slotname in stats.