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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: Robert Haas <robertmhaas@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Thomas Munro <thomas.munro@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2024-09-10T22:35:35Z
Lists: pgsql-hackers 
Hi,

On 2024-09-10 13:33:36 -0400, Robert Haas wrote:
> On Tue, Sep 10, 2024 at 12:59 PM Andres Freund <andres@anarazel.de> wrote:
> > I still think that we'd be better off to just return an error to the client in
> > postmaster, rather than deal with this dead-end children mess. That was
> > perhaps justified at some point, but now it seems to add way more complexity
> > than it's worth. And it's absurdly expensive to fork to return an error. Way
> > more expensive than just having postmaster send an error and close the socket.
> 
> The tricky case is the one where the client write() -- or SSL_write() -- blocks.

Yea, SSL definitely does make it harder. But it's not exactly rocket science
to do non-blocking SSL connection establishment. After all, we do manage to
do so in libpq...

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 Fix outdated comment; all running bgworkers are in BackendList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.