Horton

Re: Weird failure with latches in curculio on v15

Nathan Bossart <nathandbossart@gmail.com>

View thread View on postgr.es
From: Nathan Bossart <nathandbossart@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, Thomas Munro <thomas.munro@gmail.com>, Fujii Masao <fujii@postgresql.org>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-02-02T20:09:57Z
Lists: pgsql-hackers

Attachments

On Thu, Feb 02, 2023 at 01:24:15PM +0900, Michael Paquier wrote:
> On Wed, Feb 01, 2023 at 09:34:44PM -0500, Tom Lane wrote:
>> I was vaguely wondering about removing both of those functions
>> in favor of an integrated function that does a system() call
>> with those things before and after it.
> 
> It seems to me that this is pretty much the same as storing
> in_restore_command in shell_restore.c, and that for recovery modules
> this comes down to the addition of an extra callback called in
> startup.c to check if the flag is up or not.  Now the patch is doing 
> things the opposite way: like on HEAD, store the flag in startup.c but
> switch it at will with the routines in startup.c.  I find the approach
> of the patch a bit more intuitive, TBH, as that makes the interface
> simpler for other recovery modules that may want to switch the flag
> back-and-forth, and I suspect that there may be cases in recovery
> modules where we'd still want to switch the flag, but not necessarily
> link it to system().

Hm.  I don't know if we want to encourage further use of
in_restore_command since it seems to be prone to misuse.  Here's a v2 that
demonstrateѕ Tom's idea (bikeshedding on names and comments is welcome).  I
personally like this approach a bit more.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

  1. Avoid calling proc_exit() in processes forked by system().

  2. Move extra code out of the Pre/PostRestoreCommand() section.

  3. Revert refactoring of restore command code to shell_restore.c

  4. Refactor code in charge of running shell-based recovery commands

  5. Clean up inconsistent use of fflush().

  6. Report wait events for local shell commands like archive_command.