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Re: Refactoring postmaster's code to cleanup after child exit

Tomas Vondra <tomas@vondra.me>

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From: Tomas Vondra <tomas@vondra.me>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Thomas Munro <thomas.munro@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Andres Freund <andres@anarazel.de>
Date: 2024-12-10T11:39:39Z
Lists: pgsql-hackers 

On 12/10/24 11:00, Heikki Linnakangas wrote:
> On 09/12/2024 22:55, Heikki Linnakangas wrote:
>> Not sure how to fix this. A small sleep in the test would work, but in
>> principle there's no delay that's guaranteed to be enough. A more
>> robust solution would be to run a "select count(*) from
>> pg_stat_activity" and wait until the number of connections are what's
>> expected. I'll try that and see how complicated that gets..
> 
> Checking pg_stat_activity doesn't help, because the backend doesn't
> register itself in pg_stat_activity until later. A connection that's
> rejected due to connection limits never shows up in pg_stat_activity.
> 
> Some options:
> 
> 0. Do nothing
> 
> 1. Add a small sleep to the test
> 

I'd just add a short sleep. Yeah, sleeps are not great, but everything
else seems like a lot of effort just to make this one test pass under
valgrind, and I don't think it's worth it.

Can we make the sleep conditional on valgrind, so that regular builds
are not affected? I guess regular builds could fail too, but I don't
think we've seen such failures until now.


regards

-- 
Tomas Vondra

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 test name and username used in failed connection attempts

  2. tests: Don't fail due to high default timeout in postmaster/003_start_stop

  3. tests: Fix race condition in postmaster/002_connection_limits

  4. Pass MyPMChildSlot as an explicit argument to child process

  5. Assign a child slot to every postmaster child process

  6. Kill dead-end children when there's nothing else left

  7. Replace postmaster.c's own backend type codes with BackendType

  8. Use an shmem_exit callback to remove backend from PMChildFlags on exit

  9. Add test for dead-end backends

  10. Add test for connection limits

  11. Fix garbled process name on backend crash

  12. Consolidate postmaster code to launch background processes

  13. Fix comment on processes being kept over a restart

  14. Refactor code to handle death of a backend or bgworker in postmaster

  15. Make BackgroundWorkerList doubly-linked

  16. Minor refactoring of assign_backendlist_entry()

  17. Fix outdated comment; all running bgworkers are in BackendList

  18. Allow building with MSVC and Strawberry perl

  19. Fix rare failure in LDAP tests.

  20. Allow notifications to bgworkers without database connections.