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

Hello!

On 06.12.2022 21:44, Andres Freund wrote:
> Hi,
> 
> On 2022-09-19 01:29:21 +0300, Anton A. Melnikov wrote:
>> Corrected patch is attached (v2-0001-Fix-burst-checkpoint_req-growth.patch).
> 
> This patch doesn't pass the main regression tests tests successfully:
> 
> https://cirrus-ci.com/task/5502700019253248
> 
> diff -U3 /tmp/cirrus-ci-build/src/test/regress/expected/rules.out /tmp/cirrus-ci-build/build/testrun/regress/regress/results/rules.out
> --- /tmp/cirrus-ci-build/src/test/regress/expected/rules.out	2022-12-06 05:49:53.687424000 +0000
> +++ /tmp/cirrus-ci-build/build/testrun/regress/regress/results/rules.out	2022-12-06 05:53:04.642690000 +0000
> @@ -1816,6 +1816,9 @@
>      FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
>   pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
>       pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
> +    pg_stat_get_bgwriter_timed_restartpoints() AS restartpoints_timed,
> +    pg_stat_get_bgwriter_requested_restartpoints() AS restartpoints_req,
> +    pg_stat_get_bgwriter_performed_restartpoints() AS restartpoints_done,
>       pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
>       pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
>       pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
> 
> Greetings,
> 
> Andres Freund

Thank you for pointing!

I didn't think that the patch tester would apply both patch variants simultaneously,
assuming that these are two different possible solutions of the problem.
But it's even good, let it check both at once!

There was an error in the second variant (Add-restartpoint-stats), i forgot to correct the rules.out.
So fixed the second variant and rebased the first one (Fix-burst-checkpoint_req-growth)
to the current master.


With the best wishes,

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