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

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Alexander Lakhin <exclusion@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-05-05T03:44:47Z
Lists: pgsql-hackers

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On Wednesday, May 3, 2023 3:17 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> On Tue, May 2, 2023 at 9:46 AM Amit Kapila <amit.kapila16@gmail.com>
> wrote:
> >
> > On Tue, May 2, 2023 at 9:06 AM Zhijie Hou (Fujitsu)
> > <houzj.fnst@fujitsu.com> wrote:
> > >
> > > On Friday, April 28, 2023 2:18 PM Masahiko Sawada
> <sawada.mshk@gmail.com> 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

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix invalid memory access during the shutdown of the parallel apply worker.

  2. Fix assertion failure in apply worker.

  3. Use elog to report unexpected action in handle_streamed_transaction().

  4. Use appropriate wait event when sending data in the apply worker.

  5. Allow the logical_replication_mode to be used on the subscriber.

  6. Rename GUC logical_decoding_mode to logical_replication_mode.

  7. Display the leader apply worker's PID for parallel apply workers.

  8. Improve the code to decide and process the apply action.

  9. Document the newly added wait events added by commit 216a784829.

  10. Perform apply of large transactions by parallel workers.

  11. Wake up a subscription's replication worker processes after DDL.

  12. Add copyright notices to meson files

  13. Better document logical replication parameters

  14. Add a common function to generate the origin name.

  15. Harmonize parameter names in storage and AM code.

  16. Avoid using list_length() to test for empty list.

  17. Improve two comments related to a boolean DefElem's value

  18. Fix partition table's REPLICA IDENTITY checking on the subscriber.

  19. Fix data inconsistency between publisher and subscriber.

  20. Fix cache look-up failures while applying changes in logical replication.