Hi Amit,
> > I checked other flags that are set by signal handlers, their datatype seemed to
> be sig_atomic_t.
> > Is there any reasons that you use normal bool? It should be changed if not.
> >
>
> It follows the logic similar to ParallelMessagePending. Do you see any
> problem with it?
Hmm, one consideration is:
what will happen if the signal handler HandleParallelApplyMessageInterrupt() is fired during
"ParallelApplyMessagePending= false;"?
IIUC sig_atomic_t has been needed to avoid writing to same data at the same time.
According to C99 standard(I grepped draft version [1]), the behavior seems to be undefined if the signal handler
attaches to not "volatile sig_atomic_t" data.
...But I'm not sure whether this is really problematic in the current system, sorry...
```
If the signal occurs other than as the result of calling the abort or raise function,
the behavior is undefined if the signal handler refers to any object with static storage duration other than by
assigninga value to an object declared as volatile sig_atomic_t,
or the signal handler calls any function in the standard library other than the abort function,
the _Exit function, or the signal function with the first argument equal to the signal number corresponding to the
signalthat caused the invocation of the handler.
```
> > a.
> > I was not sure when the cell should be cleaned. Currently we clean up
> ParallelApplyWorkersList() only in the parallel_apply_start_worker(),
> > but we have chances to remove such a cell like HandleParallelApplyMessages()
> or HandleParallelApplyMessage(). How do you think?
> >
>
> Note that HandleParallelApply* are invoked during interrupt handling,
> so it may not be advisable to remove it there.
>
> >
> > 12. ConfigureNamesInt
> >
> > ```
> > + {
> > + {"max_parallel_apply_workers_per_subscription",
> > + PGC_SIGHUP,
> > + REPLICATION_SUBSCRIBERS,
> > + gettext_noop("Maximum number of parallel apply
> workers per subscription."),
> > + NULL,
> > + },
> > + &max_parallel_apply_workers_per_subscription,
> > + 2, 0, MAX_BACKENDS,
> > + NULL, NULL, NULL
> > + },
> > ```
> >
> > This parameter can be changed by pg_ctl reload, so the following corner case
> may be occurred.
> > Should we add a assign hook to handle this? Or, can we ignore it?
> >
>
> I think we can ignore this as it will eventually start respecting the threshold.
Both of you said are reasonable for me.
[1]: https://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf
Best Regards,
Hayato Kuroda
FUJITSU LIMITED
