RE: Perform streaming logical transactions by background workers and parallel apply

On Wednesday, May 3, 2023 3:17 PM Amit Kapila  wrote:
> 
> On Tue, May 2, 2023 at 9:46 AM Amit Kapila 
> wrote:
> >
> > On Tue, May 2, 2023 at 9:06 AM Zhijie Hou (Fujitsu)
> >  wrote:
> > >
> > > On Friday, April 28, 2023 2:18 PM Masahiko Sawada
>  wrote:
> > > >
> > > > >
> > > > > Alexander, does the proposed patch fix the problem you are facing?
> > > > > Sawada-San, and others, do you see any better way to fix it than
> > > > > what has been proposed?
> > > >
> > > > I'm concerned that the idea of relying on IsNormalProcessingMode()
> > > > might not be robust since if we change the meaning of
> > > > IsNormalProcessingMode() some day it would silently break again.
> > > > So I prefer using something like InitializingApplyWorker, or
> > > > another idea would be to do cleanup work (e.g., fileset deletion
> > > > and lock release) in a separate callback that is registered after
> > > > connecting to the database.
> > >
> > > Thanks for the review. I agree that it’s better to use a new variable here.
> > > Attach the patch for the same.
> > >
> >
> > + *
> > + * However, if the worker is being initialized, there is no need to
> > + release
> > + * locks.
> >   */
> > - LockReleaseAll(DEFAULT_LOCKMETHOD, true);
> > + if (!InitializingApplyWorker)
> > + LockReleaseAll(DEFAULT_LOCKMETHOD, true);
> >
> > Can we slightly reword this comment as: "The locks will be acquired
> > once the worker is initialized."?
> >
> 
> After making this modification, I pushed your patch. Thanks!

Thanks for pushing.

Attach another patch to fix the problem that pa_shutdown will access invalid
MyLogicalRepWorker. I personally want to avoid introducing new static variable,
so I only reorder the callback registration in this version.

When testing this, I notice a rare case that the leader is possible to receive
the worker termination message after the leader stops the parallel worker. This
is unnecessary and have a risk that the leader would try to access the detached
memory queue. This is more likely to happen and sometimes cause the failure in
regression tests after the registration reorder patch because the dsm is
detached earlier after applying the patch.

So, put the patch that detach the error queue before stopping worker as 0001
and the registration reorder patch as 0002.

Best Regards,
Hou zj