Re: pg_get_wal_replay_pause_state() should not return 'paused' while a promotion is ongoing.

On 2021/05/18 9:58, Kyotaro Horiguchi wrote:
> At Mon, 17 May 2021 23:29:18 +0900, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote in
>> If a promotion is triggered while recovery is paused, the paused state
>> ends
>> and promotion continues. But currently pg_get_wal_replay_pause_state()
>> returns 'paused' in that case. Isn't this a bug?
>>
>> Attached patch fixes this issue by resetting the recovery pause state
>> to
>> 'not paused' when standby promotion is triggered.
>>
>> Thought?
>
> Nice catch!
>
> Once the state enteres "paused" state no more WAL record is expected
> to be replayed until exiting the state. I'm not sure but maybe we are
> also expecting that the server promotes whthout a record replayed when
> triggered while pausing.

Currently a promotion causes all available WAL to be replayed before
a standby becomes a primary whether it was in paused state or not.
OTOH, something like immediate promotion (i.e., standby becomes
a primary without replaying outstanding WAL) might be useful for
some cases. I don't object to that.

Regards,

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