Horton

Re: Replication slot stats misgivings

vignesh C <vignesh21@gmail.com>

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From: vignesh C <vignesh21@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-03-30T04:43:29Z
Lists: pgsql-hackers 
On Tue, Mar 30, 2021 at 6:28 AM Andres Freund <andres@anarazel.de> wrote:
>
> Hi,
>
> On 2021-03-26 07:58:58 +0530, Amit Kapila wrote:
> > On Fri, Mar 26, 2021 at 1:17 AM Andres Freund <andres@anarazel.de> wrote:
> > > I suggest we wait doing anything about this until we know if the shared
> > > stats patch gets in or not (I'd give it 50% maybe). If it does get in
> > > things get a good bit easier, because we don't have to deal with the
> > > message loss issues anymore.
> > >
> >
> > Okay, that makes sense.
>
> Any chance you could write a tap test exercising a few of these cases?

I can try to write a patch for this if nobody objects.

> E.g. things like:
>
> - create a few slots, drop one of them, shut down, start up, verify
>   stats are still sane
> - create a few slots, shut down, manually remove a slot, lower
>   max_replication_slots, start up

Here by "manually remove a slot", do you mean to remove the slot
manually from the pg_replslot folder?

> IMO, independent of the shutdown / startup issue, it'd be worth writing
> a patch tracking the bytes sent independently of the slot stats storage
> issues. That would also make the testing for the above cheaper...

I can try to write a patch for this if nobody objects.

Regards,
Vignesh

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.