Horton

Re: May be BUG. Periodic burst growth of the checkpoint_req counter on replica.

Anton A. Melnikov <a.melnikov@postgrespro.ru>

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From: "Anton A. Melnikov" <a.melnikov@postgrespro.ru>
To: Fujii Masao <masao.fujii@oss.nttdata.com>, Alexander Korotkov <aekorotkov@gmail.com>
Cc: Magnus Hagander <magnus@hagander.net>, "Anton A. Melnikov" <aamelnikov@inbox.ru>, Andres Freund <andres@anarazel.de>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2024-09-30T07:00:00Z
Lists: pgsql-hackers 
On 30.09.2024 06:26, Fujii Masao wrote:
> Thanks for the review! I've pushed the 0001 patch.

Thanks a lot!

>> As for switching in the pg_proc.dat entries the idea was to put them in order
>> so that the pg_stat_get_checkpointer* functions were grouped together.
>> I don't know if this is the common and accepted practice. Simply i like it better this way.
>> Sure, if you think it's unnecessary, let it stay as is with minimal diff.
> 
> I understand your point, but I didn't made that change to keep the diff minimal,
> which should make future back-patching easier.

Agreed. Its quite reasonable. I've not take into account the backporting
possibility at all. This is of course wrong.

>> In addition, checkpoints may be skipped due to "checkpoints are occurring
>> too frequently" error. Not sure, but maybe add this information to
>> the new description?
> 
>  From what I can see in the code, that error message doesn’t seem to indicate
> the checkpoint is being skipped. In fact, checkpoints are still happening
> actually when that message appears. Am I misunderstanding something?

No, you are right! This is my oversight. I didn't notice that elevel is just a log
not a error. Thanks!


With the best wishes,
   

-- 
Anton A. Melnikov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

Commits

  1. Improve descriptions of some pg_stat_checkpoints functions in pg_proc.dat.

  2. docs: Enhance the pg_stat_checkpointer view documentation.

  3. Add num_done counter to the pg_stat_checkpointer view.

  4. docs: Improve the description of num_timed column in pg_stat_checkpointer.

  5. Improve documentation for pg_stat_checkpointer fields

  6. Enhance checkpointer restartpoint statistics

  7. Introduce pg_stat_checkpointer