Re: Allow interrupts on waiting standby

Hi Michael, Simon,

From: pgsql-hackers-owner@postgresql.org
> [mailto:pgsql-hackers-owner@postgresql.org] On Behalf Of Michael Paquier
> > Oh, I see.  But how does the startup process respond quickly?  It seems
> that you need to call HandleStartupProcInterrupts() instead of
> CHECK_FOR_INTERRUPTS().  But I'm not sure whether
> HandleStartupProcInterrupts() can be called here.
> 
> Bah. Of course you are right. We don't care about SetLatch() here as signals
> are processed with a different code path than normal backends.

So, I understood you agreed that CHECK_FOR_INTERRUPTS() here does nothing.  But your patch still calls it:

+    /* An interrupt may have occurred while waiting */
+    CHECK_FOR_INTERRUPTS();

I got confused because the problem is not defined in this thread.  What problem does this patch address?  These ones?

* The startup process terminates as soon as postmaster dies.
* pg_stat_activity does not show the wait event of startup process waiting for a recovery conflict resolution.


My guess about why you decided to not call HandleStartupProcInterrupts() here is:

* Respond to postmaster death here.
* No need to reload config file here because there's no parameter to affect this conflict wait.  But
max_standby_{archive| streaming}_delay seems to affect the wait period.
 
* No need to handle SIGTERM and exit here, because the startup process doesn't wait for a conflict resolution here when
hecan terminate.
 

I think you can call HandleStartupProcInterrupts() here, instead of checking postmaster death.  Did you perform tests?

Did Simon's committed patch solve the problem as expected?

Regards
Takayuki Tsunakawa