Re: recovery modules

On Tue, Mar 14, 2023 at 09:13:09PM -0700, Nathan Bossart wrote:
> However, that's not what happens when hot_standby is off.  In that case,
> the postmaster.pid file is updated with PM_STATUS_STANDBY once recovery
> starts, which wait_for_postmaster_start() interprets as "ready."  I see
> this was reported before [0], but that discussion fizzled out.  IIUC it was
> done this way to avoid infinite waits when hot_standby is off and standby
> mode is enabled.  I could be missing something obvious, but that doesn't
> seem necessary when hot_standby is off and recovery mode is enabled because
> recovery should end at some point (never mind the halting problem).  I'm
> still digging into this and may spin off a new thread if I can conjure up a
> proposal.
>
> [0] https://postgr.es/m/CAMkU%3D1wrMqPggnEfszE-c3PPLmKgRK17_qr7tmxBECYEbyV-4Q%40mail.gmail.com

These days, knowing hot_standby is on by default, and that users would
recover up to the end-of-backup record of just use read replicas, do
we have a strong case for keeping this GUC parameter at all?  It does
not strike me that we really need to change a five-year-old behavior
if there has been few complaints about it.  I agree that it is
confusing as it stands, but the long-term simplifications may be worth
it in the recovery code (aka less booleans needed to track the flow of
the startup process, and less confusion around that).
--
Michael