Re: Suppressing useless wakeups in walreceiver

On Tue, Oct 11, 2022 at 8:20 AM Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:
>
> > AFICS, the aim of the patch isn't optimizing around
> > GetCurrentTimestamp() calls and the patch does seem to change quite a
> > bit of them which may cause a change of the behaviour. I think that
> > the GetCurrentTimestamp() optimizations can go to 0003 patch in this
> > thread itself or we can discuss it as a separate thread to seek more
> > thoughts.
> >
> > The 'now' in many instances in the patch may not actually represent
> > the true current time and it includes time taken by other operations
> > as well. I think this will have problems.
>
> What problems do you think this will cause?

now = t1;
XLogWalRcvSendReply() /* say it ran for a minute or so for whatever reasons */
XLogWalRcvSendHSFeedback() /* with patch walrecevier sends hot standby
feedback more often without properly honouring
wal_receiver_status_interval because the 'now' isn't actually the
current time as far as that function is concerned, it is
t1 + XLogWalRcvSendReply()'s time. */

Well, is this really a problem? I'm not sure about that. Let's hear from others.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
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