Re: Use standard SIGHUP and SIGTERM handlers in autoprewarm module

On Mon, Oct 5, 2020 at 8:04 PM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
>
> On 2020/10/05 19:45, Bharath Rupireddy wrote:
> > Hi,
> >
> > Autoprewarm module is using it's own SIGHUP(apw_sigterm_handler, got_sigterm) and SIGTERM(apw_sighup_handler, got_sighup) handlers which are similar to standard signal handlers(except for a difference [1]). Isn't it good to remove them and use standard SignalHandlerForConfigReload and SignalHandlerForShutdownRequest?
> >
> > Attaching the patch for the above changes.
> >
> > Looks like the commit[2] replaced custom handlers with standard handlers.
> >
> > Thoughts?
>
> +1
>
> The patch looks good to me.
>

Thanks.

>
> ISTM that we can also replace StartupProcSigHupHandler() in startup.c
> with SignalHandlerForConfigReload() by making the startup process use
> the general shared latch instead of its own one. POC patch attached.
> Thought?
>

I'm not quite sure whether it breaks something or not. I see that
WakeupRecovery() with XLogCtl->recoveryWakeupLatch latch from the
startup process is also being used in the walreceiver process. I may
be wrong, but have some concern if the behaviour is different in case
of EXEC_BACKEND and Windows?

Another concern is that we are always using
XLogCtl->recoveryWakeupLatch in shared mode, this makes sense as this
latch is also being used in walrecevier. But sometimes, MyLatch is
created in non-shared mode as well(see InitLatch(MyLatch)).

Others may have better thoughts though.

>
> Probably we can also replace sigHupHandler() in syslogger.c with
> SignalHandlerForConfigReload()? This would be separate patch, though.
>

+1 to replace sigHupHandler() with SignalHandlerForConfigReload() as
the latch and the functionality are pretty much the same.

WalReceiverMai(): I think we can also replace WalRcvShutdownHandler()
with SignalHandlerForShutdownRequest() because walrcv->latch point to
&MyProc->procLatch which in turn point to MyLatch.

Thoughts? If okay, we can combine these into a single patch. I will
post an updated patch soon.

With Regards,
Bharath Rupireddy.
EnterpriseDB: http://www.enterprisedb.com