Re: Support worker_spi to execute the function dynamically.

On Thu, Jul 20, 2023 at 2:38 PM Masahiro Ikeda <ikedamsh(at)oss(dot)nttdata(dot)com> wrote:
>
> Thanks for discussing about the patch. I updated the patch from your
> comments
> * v2-0001-Support-worker_spi-to-execute-the-function-dynamical.patch
>
> I found another thing to be changed better. Though the tests was assumed
> "shared_preload_libraries = worker_spi", the background workers failed
> to
> be launched in initialized phase because the database is not created
> yet.
>
> ```
> # make check # in src/test/modules/worker_spi
> # cat log/postmaster.log # in src/test/modules/worker_spi/
> 2023-07-20 17:58:47.958 JST worker_spi[853620] FATAL: database
> "contrib_regression" does not exist
> 2023-07-20 17:58:47.958 JST worker_spi[853621] FATAL: database
> "contrib_regression" does not exist
> 2023-07-20 17:58:47.959 JST postmaster[853612] LOG: background worker
> "worker_spi" (PID 853620) exited with exit code 1
> 2023-07-20 17:58:47.959 JST postmaster[853612] LOG: background worker
> "worker_spi" (PID 853621) exited with exit code 1
> ```
>
> It's better to remove "shared_preload_libraries = worker_spi" from the
> test configuration. I misunderstood that two background workers would
> be launched and waiting at the start of the test.

I don't think that change is correct. The worker_spi essentially shows
how to start bg workers with RegisterBackgroundWorker and dynamic bg
workers with RegisterDynamicBackgroundWorker. If
shared_preload_libraries = worker_spi not specified in there, you will
miss to start RegisterBackgroundWorkers. Is giving an initidb time
database name to worker_spi.database work there? If the database for
bg workers doesn't exist, changing bgw_restart_time from
BGW_NEVER_RESTART to say 1 will help to see bg workers coming up
eventually.

I think it's worth adding test cases for the expected number of bg
workers (after creating worker_spi extension) and dynamic bg workers
(after calling worker_spi_launch()). Also, to distinguish bg workers
and dynamic bg workers, you can change
bgw_type in worker_spi_launch to "worker_spi dynamic worker".

- /* get the configuration */
+ /* Get the configuration */

- /* set up common data for all our workers */
+ /* Set up common data for all our workers */

These unrelated changes better be there as-is. Because, the postgres
code has both commenting styles /* Get .... */ or /* get ....*/, IOW,
single line comments starting with both uppercase and lowercase.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com