Re: recovery modules

From: Nathan Bossart <nathandbossart(at)gmail(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: recovery modules
Date: 2023-02-16 21:58:10
Message-ID: 20230216215810.GA2356244@nathanxps13
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On Thu, Feb 16, 2023 at 01:17:54PM -0800, Andres Freund wrote:
> On 2023-02-16 12:15:12 -0800, Nathan Bossart wrote:
>> On Thu, Feb 16, 2023 at 11:29:56AM -0800, Andres Freund wrote:
>> > On 2023-02-15 10:44:07 -0800, Nathan Bossart wrote:
>> >> @@ -144,10 +170,12 @@ basic_archive_configured(void)
>> >> * Archives one file.
>> >> */
>> >> static bool
>> >> -basic_archive_file(const char *file, const char *path)
>> >> +basic_archive_file(ArchiveModuleState *state, const char *file, const char *path)
>> >> {
>> >> sigjmp_buf local_sigjmp_buf;
>> >
>> > Not related the things changed here, but this should never have been pushed
>> > down into individual archive modules. There's absolutely no way that we're
>> > going to keep this up2date and working correctly in random archive
>> > modules. And it would break if archive modules are ever called outside of
>> > pgarch.c.
>> Yeah. IIRC I did briefly try to avoid this, but the difficulty was that
>> each module will have its own custom cleanup logic.
> It can use PG_TRY/CATCH for that, if the top-level sigsetjmp is in pgarch.c.
> Or you could add a cleanup callback to the API, to be called after the
> top-level cleanup in pgarch.c.

Yeah, that seems workable.

> I'm quite baffled by:
> /* Close any files left open by copy_file() or compare_files() */
> AtEOSubXact_Files(false, InvalidSubTransactionId, InvalidSubTransactionId);
> in basic_archive_file(). It seems *really* off to call AtEOSubXact_Files()
> completely outside the context of a transaction environment. And it only does
> the thing you want because you pass parameters that aren't actually valid in
> the normal use in AtEOSubXact_Files(). I really don't understand how that's
> supposed to be ok.

Hm. Should copy_file() and compare_files() have PG_FINALLY blocks that
attempt to close the files instead? What would you recommend?

Nathan Bossart
Amazon Web Services:

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