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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: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, Amit Kapila <amit.kapila16@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-11-27T04:16:15Z
Lists: pgsql-hackers 
On Tuesday, November 22, 2022 9:53 PM Kuroda, Hayato <kuroda.hayato@fujitsu.com> wroteL
> 
> Thanks for updating the patch!
> I tested the case whether the deadlock caused by foreign key constraint could
> be detected, and it worked well.
> 
> Followings are my review comments. They are basically related with 0001, but
> some contents may be not. It takes time to understand 0002 correctly...

Thanks for the comments!

> 01. typedefs.list
> 
> LeaderFileSetState should be added to typedefs.list.
> 
> 
> 02. 032_streaming_parallel_apply.pl
> 
> As I said in [1]: the test name may be not matched. Do you have reasons to
> revert the change?

The original parallel safety check has been removed, so I changed the name.
After rethinking about this, I named it to stream_parallel_conflict.

> 
> 03. 032_streaming_parallel_apply.pl
> 
> The test does not cover the case that the backend process relates with the
> deadlock. IIUC this is another motivation to use a stream/transaction lock.
> I think it should be added.

The main deadlock cases that stream/transaction lock can detect is 1) LA->PA 2)
LA->PA->PA as explained atop applyparallelworker.c. So I think backend process
related one is a variant which I think have been covered by the existing
tests in the patch.

> 04. log output
> 
> While being applied spooled changes by PA, there are so many messages like
> "replayed %d changes from file..." and "applied %u changes...". They comes
> from
> apply_handle_stream_stop() and apply_spooled_messages(). They have same
> meaning, so I think one of them can be removed.

Changed.

> 05. system_views.sql
> 
> In the previous version you modified pg_stat_subscription system view. Why
> do you revert that?

I was not sure should we include that in the main patch set.
I added a top-up patch that change the view.

> 06. interrupt.c - SignalHandlerForShutdownRequest()
> 
> In the comment atop SignalHandlerForShutdownRequest(), some processes
> that assign the function except SIGTERM are clarified. We may be able to add
> the parallel apply worker.

Changed


> 08. guc_tables.c - ConfigureNamesInt
> 
> ```
>                 &max_sync_workers_per_subscription,
> +               2, 0, MAX_PARALLEL_WORKER_LIMIT,
> +               NULL, NULL, NULL
> +       },
> ```
> 
> The upper limit for max_sync_workers_per_subscription seems to be wrong, it
> should be used for max_parallel_apply_workers_per_subscription.

That's my miss, sorry for that.

> 10. worker.c - maybe_reread_subscription()
> 
> 
> ```
> +               if (am_parallel_apply_worker())
> +                       ereport(LOG,
> +                       /* translator: first %s is the name of logical replication
> worker */
> +                                       (errmsg("%s for subscription \"%s\"
> will stop because of a parameter change",
> +
> + get_worker_name(), MySubscription->name)));
> ```
> 
> I was not sure get_worker_name() is needed. I think "logical replication apply
> worker"
> should be embedded.

Changed.

> 
> 11. worker.c - ApplyWorkerMain()
> 
> ```
> +                               (errmsg_internal("%s for subscription \"%s\"
> two_phase is %s",
> +
> + get_worker_name(),
> ```

Changed


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.