From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
Cc: | Michael Paquier <michael(at)paquier(dot)xyz>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: recovery modules |
Date: | 2023-02-13 23:37:33 |
Message-ID: | 20230213233733.dsiaxtbr5nvskq46@awork3.anarazel.de |
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Lists: | pgsql-hackers |
Hi,
On 2023-02-13 14:56:47 -0800, Nathan Bossart wrote:
> On Mon, Feb 13, 2023 at 04:37:10PM +0900, Michael Paquier wrote:
> > + basic_archive_context = data->context;
> > + if (CurrentMemoryContext == basic_archive_context)
> > + MemoryContextSwitchTo(TopMemoryContext);
> > +
> > + if (MemoryContextIsValid(basic_archive_context))
> > + MemoryContextDelete(basic_archive_context);
> >
> > This is a bit confusing, because it means that we enter in the
> > shutdown callback with one context, but exit it under
> > TopMemoryContext. Are you sure that this will be OK when there could
> > be multiple callbacks piled up with before_shmem_exit()? shmem_exit()
> > has nothing specific to memory contexts.
>
> Well, we can't free the memory context while we are in it, so we have to
> switch to another one. I agree that this is a bit confusing, though.
Why would we be in that memory context? I'd just add an assert documenting
we're not.
> On second thought, I'm not sure it's important to make sure the state is
> freed in the shutdown callback. It's only called just before the archiver
> process exits, so we're not really at risk of leaking anything. I suppose
> we might not always restart the archiver in this case, but I also don't
> anticipate that behavior changing in the near future. I think this
> callback is more useful for things like shutting down background workers.
I think it's crucial. Otherwise we're just ossifying the design that there's
just one archive module active at a time.
> I went ahead and removed the shutdown callback from basic_archive and the
> note about leaking from the documentation.
-1
Greetings,
Andres Freund
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