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

Heikki Linnakangas <hlinnaka@iki.fi>

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From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Tomas Vondra <tomas@vondra.me>
Cc: Thomas Munro <thomas.munro@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Andres Freund <andres@anarazel.de>
Date: 2024-12-09T12:30:25Z
Lists: pgsql-hackers 
On 09/12/2024 01:12, Tomas Vondra wrote:
> On 11/14/24 15:13, Heikki Linnakangas wrote:
>> On 09/10/2024 23:40, Heikki Linnakangas wrote:
>>> I pushed the first three patches, with the new test and one of the small
>>> refactoring patches. Thanks for all the comments so far! Here is a new
>>> version of the remaining patches.
>>>
> Hi, the TAP test 001_connection_limits.pl introduced by 6a1d0d470e84
> seems to have problems with valgrind :-( I reliably get this failure:

How exactly do you run the test with valgrind? What platform?

It works for me, with this:

(cd build && ninja && rm -rf tmp_install && meson test --suite setup && 
valgrind --leak-check=no --gen-suppressions=all 
--suppressions=/home/heikki/git-sandbox/postgresql/src/tools/valgrind.supp 
--time-stamp=yes 
--error-markers=VALGRINDERROR-BEGIN,VALGRINDERROR-END 
--log-file=$HOME/pg-valgrind/%p.log --trace-children=yes meson test 
--suite postmaster )

> t/001_connection_limits.pl .. 3/? # Tests were run but no plan was
> declared and done_testing() was not seen.
> # Looks like your test exited with 29 just after 4.
> t/001_connection_limits.pl .. Dubious, test returned 29 (wstat 7424, 0x1d00)
> All 4 subtests passed
> 
> 
> and tmp_check/log/regress_log_001_connection_limits says:
> 
> 
> [23:48:44.444](1.129s) ok 3 - reserved_connections limit
> [23:48:44.445](0.001s) ok 4 - reserved_connections limit: matches
> process ended prematurely at
> /home/user/work/postgres/src/test/postmaster/../../../src/test/perl/PostgreSQL/Test/BackgroundPsql.pm
> line 154.
> # Postmaster PID for node "primary" is 198592
> 
> 
> That BackgroundPsql.pm line is this in wait_connect()
> 
>    $self->{run}->pump()
>      until $self->{stdout} =~ /$banner/ || $self->{timeout}->is_expired;
> 
> By trial and error I found that it fails on this line 70:
> 
>    push(@sessions, background_psql_as_user('regress_superuser'));
> 
> but I have no idea idea why. There are multiple similar calls a couple
> lines earlier, and those work fine. And various other TAP tests with
> background_sql() work fine too.
> 
> So what's so special about this particular line?

Weird. Valgrind makes everything slow; is it a timeout? Any other clues 
in the logs?

-- 
Heikki Linnakangas
Neon (https://neon.tech)

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.