Re: Suppressing useless wakeups in walreceiver - Mailing list pgsql-hackers

From Thomas Munro
Subject Re: Suppressing useless wakeups in walreceiver
Date
Msg-id CA+hUKGLaxEoSjU6qtQZ-bmPM1WszqyESjHf1iejASTHv1hjhnQ@mail.gmail.com
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In response to Re: Suppressing useless wakeups in walreceiver  (Nathan Bossart <nathandbossart@gmail.com>)
List pgsql-hackers
On Wed, Nov 16, 2022 at 5:24 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
> On Wed, Nov 16, 2022 at 04:57:08PM +1300, Thomas Munro wrote:
> > On Tue, Nov 15, 2022 at 5:49 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
> >> Another option might be to just force initial reply/feedback messages when
> >> streaming starts.  The attached patch improves src/test/recovery test
> >> runtime just like the previous one I posted.
> >
> > Yeah, looks good in my tests.  I think we just need to make it
> > conditional so we don't force it if someone has
> > wal_receiver_status_interval disabled.
>
> Yeah, that makes sense.  IIUC setting "force" to false would have the same
> effect for the initial round of streaming, but since writePtr/flushPtr will
> be set in later rounds, no reply would be guaranteed.  That might be good
> enough for the tests, but it seems a bit inconsistent.  So, your patch is
> probably the way to go.

On second thoughts, there's not much point in that, since we always
force replies under various other circumstances anyway.  There isn't
really a 'never send replies' mode.  Committed the way you had it
before.  Thanks!

I can't unsee that we're spending ~35 seconds waiting for catchup in
718 separate wait_for_catchup calls.  The problem is entirely on the
waiting side (we already do WalRcvForceReply() in xlogrecovery.c when
going idle), and there's probably a nice condition variable-based
improvement here but I decided to hop over that rabbit hole today.



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