Buildfarm members gaur, pademelon, and gharial have all recently shown
failures like this:
***
/home/bfarm/bf-data/HEAD/pgsql.build/src/test/regress/expected/select_parallel.out
Thu Feb 16 20:35:14 2017
---
/home/bfarm/bf-data/HEAD/pgsql.build/src/test/regress/results/select_parallel.out
Thu Feb 16 21:17:58 2017
***************
*** 163,167 ****
-- provoke error in worker
select stringu1::int2 from tenk1 where unique1 = 1;
ERROR: invalid input syntax for integer: "BAAAAA"
- CONTEXT: parallel worker
rollback;
--- 163,166 ----
======================================================================
The failure appears intermittent on gharial but is quite reproducible
on gaur/pademelon. I inserted some debug elog calls and got this trace
of events:
2017-02-17 00:28:32.641 EST [18934] LOG: RegisterDynamicBackgroundWorker:
grabbing slot 1
2017-02-17 00:28:32.641 EST [18934] STATEMENT: select count(*) from a_star;
2017-02-17 00:28:32.643 EST [18934] LOG: LaunchParallelWorkers: registered 1
of 1 workers
2017-02-17 00:28:32.643 EST [18934] STATEMENT: select count(*) from a_star;
2017-02-17 00:28:32.731 EST [18934] LOG: RegisterDynamicBackgroundWorker:
grabbing slot 2
2017-02-17 00:28:32.731 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:32.824 EST [18934] LOG: LaunchParallelWorkers: registered 1
of 4 workers
2017-02-17 00:28:32.824 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:32.824 EST [18934] LOG: RegisterDynamicBackgroundWorker:
grabbing slot 3
2017-02-17 00:28:32.824 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:32.923 EST [18934] LOG: LaunchParallelWorkers: registered 2
of 4 workers
2017-02-17 00:28:32.923 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:32.923 EST [18934] LOG: RegisterDynamicBackgroundWorker:
grabbing slot 4
2017-02-17 00:28:32.923 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:32.989 EST [18934] LOG: LaunchParallelWorkers: registered 3
of 4 workers
2017-02-17 00:28:32.989 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:32.989 EST [18934] LOG: RegisterDynamicBackgroundWorker:
grabbing slot 5
2017-02-17 00:28:32.989 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:33.040 EST [18934] LOG: LaunchParallelWorkers: registered 4
of 4 workers
2017-02-17 00:28:33.040 EST [18934] STATEMENT: select length(stringu1) from
tenk1 group by length(stringu1);
2017-02-17 00:28:33.093 EST [18934] LOG: RegisterDynamicBackgroundWorker:
grabbing slot 6
2017-02-17 00:28:33.093 EST [18934] STATEMENT: select count(*) from tenk1
where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
2017-02-17 00:28:33.173 EST [18934] LOG: LaunchParallelWorkers: registered 1
of 4 workers
2017-02-17 00:28:33.173 EST [18934] STATEMENT: select count(*) from tenk1
where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
2017-02-17 00:28:33.173 EST [18934] LOG: RegisterDynamicBackgroundWorker:
grabbing slot 7
2017-02-17 00:28:33.173 EST [18934] STATEMENT: select count(*) from tenk1
where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
2017-02-17 00:28:33.253 EST [18934] LOG: LaunchParallelWorkers: registered 2
of 4 workers
2017-02-17 00:28:33.253 EST [18934] STATEMENT: select count(*) from tenk1
where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
2017-02-17 00:28:33.253 EST [18934] LOG: RegisterDynamicBackgroundWorker: no
free slots of 8
2017-02-17 00:28:33.253 EST [18934] STATEMENT: select count(*) from tenk1
where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
2017-02-17 00:28:33.254 EST [18934] LOG: LaunchParallelWorkers: failed to
register 3 of 4 workers
2017-02-17 00:28:33.254 EST [18934] STATEMENT: select count(*) from tenk1
where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
2017-02-17 00:28:33.557 EST [18934] LOG: RegisterDynamicBackgroundWorker: no
free slots of 8
2017-02-17 00:28:33.557 EST [18934] STATEMENT: select count((unique1)) from
tenk1 where hundred > 1;
2017-02-17 00:28:33.557 EST [18934] LOG: LaunchParallelWorkers: failed to
register 1 of 4 workers
2017-02-17 00:28:33.557 EST [18934] STATEMENT: select count((unique1)) from
tenk1 where hundred > 1;
2017-02-17 00:28:33.703 EST [18934] LOG: RegisterDynamicBackgroundWorker: no
free slots of 8
2017-02-17 00:28:33.703 EST [18934] STATEMENT: select stringu1::int2 from
tenk1 where unique1 = 1;
2017-02-17 00:28:33.703 EST [18934] LOG: LaunchParallelWorkers: failed to
register 1 of 1 workers
2017-02-17 00:28:33.703 EST [18934] STATEMENT: select stringu1::int2 from
tenk1 where unique1 = 1;
2017-02-17 00:28:33.704 EST [18934] ERROR: invalid input syntax for integer:
"BAAAAA"
2017-02-17 00:28:33.704 EST [18934] STATEMENT: select stringu1::int2 from
tenk1 where unique1 = 1;
2017-02-17 00:28:33.854 EST [18336] LOG: ForgetBackgroundWorker: unregistering
background worker "parallel worker for PID 18934" slot 7
2017-02-17 00:28:33.854 EST [18336] LOG: ForgetBackgroundWorker: unregistering
background worker "parallel worker for PID 18934" slot 6
2017-02-17 00:28:33.854 EST [18336] LOG: ForgetBackgroundWorker: unregistering
background worker "parallel worker for PID 18934" slot 5
2017-02-17 00:28:33.854 EST [18336] LOG: ForgetBackgroundWorker: unregistering
background worker "parallel worker for PID 18934" slot 4
2017-02-17 00:28:33.854 EST [18336] LOG: ForgetBackgroundWorker: unregistering
background worker "parallel worker for PID 18934" slot 3
2017-02-17 00:28:33.854 EST [18336] LOG: ForgetBackgroundWorker: unregistering
background worker "parallel worker for PID 18934" slot 2
2017-02-17 00:28:33.855 EST [18336] LOG: ForgetBackgroundWorker: unregistering
background worker "parallel worker for PID 18934" slot 1
In short, it looks to me like ExecShutdownGatherWorkers doesn't actually
wait for parallel workers to finish (as its comment suggests is
necessary), so that on not-too-speedy machines the worker slots may all
still be in use when the next command wants some. This does not seem
like a good thing from a reproducibility or error-detection standpoint.
It is *certainly* not what you would expect from reading any of the
comments in the vicinity.
I don't know if this is a generic logic failure or if there's something
platform-specific about it --- it's suspicious that it's only showing up
on ia64 and hppa architectures.
I also find it curious that nobody had seen this at all until the past
couple days. I suspect that 51ee6f316 changed the number of parallel
workers demanded by the select_parallel regression test, which is, shall
we say, not what its commit log message would suggest.
regards, tom lane
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