Horton

Re: standby promotion can create unreadable WAL

Sami Imseih <simseih@amazon.com>

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From: "Imseih (AWS), Sami" <simseih@amazon.com>
To: Robert Haas <robertmhaas@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, "Alvaro Herrera" <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>
Date: 2022-08-26T15:59:10Z
Lists: pgsql-hackers 
>    I agree. Testing StandbyMode here seems bogus. I thought initially
>    that the test should perhaps be for InArchiveRecovery rather than
>    ArchiveRecoveryRequested, but I see that the code which switches to a
>    new timeline cares about ArchiveRecoveryRequested, so I think that is
>    the correct thing to test here as well.

>    Concretely, I propose the following patch.

This  patch looks similar to the change suggested in 
https://www.postgresql.org/message-id/FB0DEA0B-E14E-43A0-811F-C1AE93D00FF3%40amazon.com
to deal with panics after promoting a standby.

The difference is the patch tests !ArchiveRecoveryRequested instead
of !StandbyModeRequested as proposed in the mentioned thread.


Thanks
--
Sami Imseih
Amazon Web Services

Commits

  1. Prevent WAL corruption after a standby promotion.

  2. Use correct LSN for error reporting in pg_walinspect