Horton

Re: failures in t/031_recovery_conflict.pl on CI

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@postgresql.org, Thomas Munro <thomas.munro@gmail.com>
Date: 2022-05-03T04:05:57Z
Lists: pgsql-hackers 
Hi,

On 2022-05-02 23:44:32 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > I ended up committing the extension of the test first, before the fix. I think
> > that's the cause of the failure on longfin on serinus. Let's hope the
> > situation improves with the now also committed (and backpatched) fix.
> 
> longfin's definitely not very happy: four out of six tries have ended with

Too bad :(


> psql:<stdin>:8: ERROR:  canceling statement due to conflict with recovery
> LINE 1: SELECT * FROM test_recovery_conflict_table2;
>                       ^
> DETAIL:  User was holding shared buffer pin for too long.
> timed out waiting for match: (?^:User transaction caused buffer deadlock with recovery.) at t/031_recovery_conflict.pl line 358.
> 
> 
> I can poke into that tomorrow, but are you sure that that isn't an
> expectable result?

It's not expected. But I think I might see what the problem is:

$psql_standby{stdin} .= qq[
    BEGIN;
    -- hold pin
    DECLARE $cursor1 CURSOR FOR SELECT a FROM $table1;
    FETCH FORWARD FROM $cursor1;
    -- wait for lock held by prepared transaction
    SELECT * FROM $table2;
    ];
ok( pump_until(
		$psql_standby{run},     $psql_timeout,
		\$psql_standby{stdout}, qr/^1$/m,),
	"$sect: cursor holding conflicting pin, also waiting for lock, established"
);

We wait for the FETCH (and thus the buffer pin to be acquired). But that
doesn't guarantee that the lock has been acquired. We can't check that with
pump_until() afaics, because there'll not be any output. But a query_until()
checking pg_locks should do the trick?

Greetings,

Andres Freund

Commits

  1. Disable 031_recovery_conflict.pl until after minor releases.

  2. Temporarily skip recovery deadlock test in back branches.

  3. Backpatch addition of pump_until() more completely.

  4. Fix timing issue in deadlock recovery conflict test.

  5. Backpatch 031_recovery_conflict.pl.

  6. Fix possibility of self-deadlock in ResolveRecoveryConflictWithBufferPin().

  7. Backpatch addition of wait_for_log(), pump_until().

  8. Add tests for recovery deadlock conflicts.

  9. Phase 3 of pgindent updates.