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

On Fri, Dec 22, 2023 at 11:04 PM Alexander Korotkov
<aekorotkov(at)gmail(dot)com> wrote:
>
> Hi, Anton!
>
> On Mon, Dec 4, 2023 at 3:50 AM Anton A. Melnikov <a(dot)melnikov(at)postgrespro(dot)ru> wrote:
>>
>> Thanks for remarks!
>>
>> On 28.11.2023 21:34, Alexander Korotkov wrote:
>> > After examining the second patch
>> > ("v2-0001-Add-restartpoint-stats.patch"), it appears that adding
>> > additional statistics as outlined in the patch is the most suitable
>> > approach to address the concerns raised. This solution provides more
>> > visibility into the system's behavior without altering its core
>> > mechanics.
>>
>> Agreed. I left only this variant of the patch and rework it due to commit 96f05261.
>> So the new counters is in the pg_stat_checkpointer view now.
>> Please see the v3-0001-add-restartpoints-stats.patch attached.
>>
>>
>> > However, it's essential that this additional functionality
>> > is accompanied by comprehensive documentation to ensure clear
>> > understanding and ease of use by the PostgreSQL community.
>> >
>> > Please consider expanding the documentation to include detailed
>> > explanations of the new statistics and their implications in various
>> > scenarios.
>>
>> In the separate v3-0002-doc-for-restartpoints-stats.patch i added the definitions
>> of the new counters into the "28.2.15. pg_stat_checkpointer" section
>> and explanation of them with examples into the "30.5.WAL Configuration" one.
>>
>> Would be glad for any comments and and concerns.
>
>
> I made some grammar corrections to the docs and have written the commit message.
>
> I think this patch now looks good. I'm going to push this if there are no objections.

Per the docs, the sync_time, write_time and buffers_written only apply
to checkpoints, not restartpoints. Is this correct? AFAICT from a
quick look at the code they include both checkpoints and restartpoints
in which case I think the docs should be clarified to indicate that?
(Or if I'm wrong, and it doesn't include them, then shouldn't we have
separate counters for them?)

//Magnus