Re: recovery_target_action=pause with confusing hint

From: "movead(dot)li(at)highgo(dot)ca" <movead(dot)li(at)highgo(dot)ca>
To: "Fujii Masao" <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, "Sergei Kornilov" <sk(at)zsrv(dot)org>, pgsql-hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: recovery_target_action=pause with confusing hint
Date: 2020-04-01 08:58:01
Message-ID: 20200401165757150169112@highgo.ca
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>Thanks for the explanation again! Maybe I understand your point.
Great.

>As far as I read the code, in the standby mode, the startup process
>periodically checks the trigger file in WaitForWALToBecomeAvailable().
>No?
Yes it is.

>There can be small delay between the creation of the trigger file
>and the periodic call to CheckForStandbyTrigger() by the startup process.
>If you execute pg_wal_replay_pause() during that delay, it would suceed.
If there be a huge number of wal segments need a standby to rewind,
then it can not be a 'small delay'.

>But you'd like to get rid of that delay completely? In other words,
>both the startup process and the backend calling pg_wal_replay_pause()
>should detect the existence of the trigger file immdiately after
>it's created?
I want to point out the thing, the pg_wal_replay_pause() shows success but
the startup process keeping redo, it may cause something confused. So it's
better to solve the issue.

Regards,
Highgo Software (Canada/China/Pakistan)
URL : www.highgo.ca
EMAIL: mailto:movead(dot)li(at)highgo(dot)ca

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