Re: replay pause vs. standby promotion

From: Sergei Kornilov <sk(at)zsrv(dot)org>
To: Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, Atsushi Torikoshi <atorik(at)gmail(dot)com>
Cc: Jehan-Guillaume de Rorthais <jgdr(at)dalibo(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: replay pause vs. standby promotion
Date: 2020-03-26 14:37:30
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> If we don't ignore walreceiver and does try to connect to the master,
> a promotion and recovery cannot end forever since new WAL data can
> be streamed. You think this behavior is more consistent?

We have no simple point to stop replay.
Well, except for "immediately" - just one easy stop. But I agree that this is not the best option. Simple and clear, but not best one for data when we want to replay as much as possible from archive.

> IMO it's valid to replay all the WAL data available to avoid data loss
> before a promotion completes.

But in case of still working primary (with archive_command) we choose quite random time to promote. A random time when the primary did not save the new wal segment.
or even when a temporary error of restore_command occurs? We mention just cp command in docs. I know users uses cp (e.g. from NFS) without further error handling.

regards, Sergei

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