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

From: Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>
To: "Anton A(dot) Melnikov" <a(dot)melnikov(at)postgrespro(dot)ru>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>
Cc: Magnus Hagander <magnus(at)hagander(dot)net>, "Anton A(dot) Melnikov" <aamelnikov(at)inbox(dot)ru>, Andres Freund <andres(at)anarazel(dot)de>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: May be BUG. Periodic burst growth of the checkpoint_req counter on replica.
Date: 2024-09-30 17:09:31
Message-ID: ddbc4b52-da56-49b4-b2de-1e28ac49f5f2@oss.nttdata.com
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On 2024/09/30 16:00, Anton A. Melnikov wrote:
>
> 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!

Ok, so I pushed 0002.patch. Thanks for the review!

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION

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