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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tomas Vondra <tomas@vondra.me>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Noah Misch <noah@leadboat.com>, Michael Paquier <michael@paquier.xyz>, Thomas Munro <thomas.munro@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2025-03-07T17:41:24Z
Lists: pgsql-hackers 
Hi,

On 2025-03-07 18:03:04 +0100, Tomas Vondra wrote:
> On 3/7/25 16:49, Andres Freund wrote:
> > Hi,
> > 
> > On 2025-03-07 16:25:09 +0100, Tomas Vondra wrote:
> >> FWIW I keep running into this (and skink seems unhappy too). I ended up
> >> just adding a sleep(1), right before
> >>
> >> push(@sessions, background_psql_as_user('regress_superuser'));
> >>
> >> and that makes it work on all my machines (including rpi5).
> > 
> > Can you confirm that the fix attached to my prior email suffices to address
> > the issue on your machine too?  I'm planning to push the fixes soon.
> > 
> 
> Yes, the v2 fixes that too.

Cool, thanks for testing.


> I got confused by the message suggesting
> 
>   ... this pump stuff is all about getting better error messages
>   on a test failure. It doesn't help with the original issue.
> 
> which made me believe the tests will still fail, so I haven't tried the
> patches before.

That was just about 0002 (and 0001) neither fixing the race themselves, nor
being required to fix the race. 0002 does make it easier to understand what
went wrong, that's all...

Greetings,

Andres Freund

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.