Re: when the startup process doesn't (logging startup delays)

On Mon, Nov 21, 2022 at 10:37 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Sun, Nov 20, 2022 at 9:20 PM Kyotaro Horiguchi
> <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> > I prefer Robert's approach as it is more robust for future changes and
> > simple. I prefer to avoid this kind of piggy-backing and it doesn't
> > seem to be needed in this case. XLogShutdownWalRcv() looks like a
> > similar case to me and honestly I don't like it in the sense of
> > robustness but it is simpler than checking walreceiver status at every
> > site that refers to the flag.
>
> I don't understand what you want changed. Can you be more specific
> about what you mean by "Robert's approach"?
>
> I don't agree with Bharath's logic for preferring an if-test to an
> Assert. There are some cases where we think we've written the code
> correctly but also recognize that the logic is complicated enough that
> something might slip through the cracks. Then, a runtime check makes
> sense, because otherwise something real bad might happen on a
> production instance. But here, I don't think that's the main risk. I
> think the main risk is that some future patch tries to add code that
> should print startup log messages later on. That would probably be a
> coding mistake, and Assert would alert the patch author about that,
> whereas amending the if-test would just make the code do something
> differently then the author intended.
>
> But I don't feel super-strongly about this, which is why I mentioned
> both options in my previous email. I'm not clear on whether you are
> expressing an opinion on this point in particular or something more
> general.

If we place just the Assert(!StandbyMode); in
enable_startup_progress_timeout(), it fails for
begin_startup_progress_phase() in ResetUnloggedRelations() because the
InitWalRecovery(), that sets StandbyMode to true, is called before
ResetUnloggedRelations() . However, with the if (StandbyMode) {
return; }, we fail to report progress of ResetUnloggedRelations() in a
standby, which isn't a good idea at all because we only want to
disable the timeout during the recovery's main loop.

I introduced an assert-only function returning true when we're in
standby's main redo apply loop and modified the assertion to be
Assert(!InStandbyMainRedoApplyLoop()); works better but it complicates
the code a bit. FWIW, I'm attaching the v6 patch with this change.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com