Re: [HACKERS] random isolation test failures
Alvaro Herrera writes: > Excerpts from Tom Lane's message of mar sep 27 01:11:39 -0300 2011: >> Hmm, is that really an appropriate fix? I'm worried that it might mask >> event-ordering differences that actually are significant. > In the attached, it only affects the case where there is one blocking > command and another command that unblocks it; this is only exercised by > the much-beaten fk-deadlock cases. If either of the steps fails with a > deadlock error, it is reported identically, i.e. the error message is > emitted as > "error in s1u1 s2u1: ERROR: deadlock detected" > So the deadlock could have been detected in either s1u1 or s2u1; we > don't really care. Hmm. For the case of "deadlock detected", we actually don't *want* to care because the infrastructure is such that either process might report it. So I agree that this is a good fix for that case. I'm just worried whether it will obscure other situations where it's important to know which command failed. But if you're convinced there aren't any, fine. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] random isolation test failures
Excerpts from Tom Lane's message of mar sep 27 01:11:39 -0300 2011: > > Alvaro Herrera writes: > > I just tweaked isolationtester so that it collects the error messages > > and displays them all together at the end of the test. After seeing it > > run, I didn't like it -- I think I prefer something more local, so that > > in the only case where we call try_complete_step twice in the loop, we > > report any errors in either. AFAICS this would make both expected cases > > behave identically in test output. > > Hmm, is that really an appropriate fix? I'm worried that it might mask > event-ordering differences that actually are significant. In the attached, it only affects the case where there is one blocking command and another command that unblocks it; this is only exercised by the much-beaten fk-deadlock cases. If either of the steps fails with a deadlock error, it is reported identically, i.e. the error message is emitted as "error in s1u1 s2u1: ERROR: deadlock detected" So the deadlock could have been detected in either s1u1 or s2u1; we don't really care. The way error messages are reported in all the other cases is not changed, and these do not have a prefix; so if anything were to behave differently, we would find out because a spurious prefix would appear. -- Álvaro Herrera The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support isolation-fix-2.patch Description: Binary data -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] random isolation test failures
Alvaro Herrera writes: > I just tweaked isolationtester so that it collects the error messages > and displays them all together at the end of the test. After seeing it > run, I didn't like it -- I think I prefer something more local, so that > in the only case where we call try_complete_step twice in the loop, we > report any errors in either. AFAICS this would make both expected cases > behave identically in test output. Hmm, is that really an appropriate fix? I'm worried that it might mask event-ordering differences that actually are significant. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] random isolation test failures
Excerpts from Noah Misch's message of lun sep 26 21:57:40 -0300 2011: > These sporadic failures happen whenever the test case takes longer than > deadlock_timeout (currently 100ms for these tests) to setup the deadlock. I > outlined some mitigating strategies here: > http://archives.postgresql.org/message-id/20110727171438.ge18...@tornado.leadboat.com > > I'd vote for #1: let's double the deadlock_timeout until the failures stop. > Other opinions? I just tweaked isolationtester so that it collects the error messages and displays them all together at the end of the test. After seeing it run, I didn't like it -- I think I prefer something more local, so that in the only case where we call try_complete_step twice in the loop, we report any errors in either. AFAICS this would make both expected cases behave identically in test output. The only thing left to figure out is where to store the error message between calls ... clearly Step is not the right place for it. I'm on it now, anyway. -- Álvaro Herrera The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support isolation-fix.patch Description: Binary data -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] random isolation test failures
On Mon, Sep 26, 2011 at 01:10:27PM -0400, Tom Lane wrote:
> Andrew Dunstan writes:
> > We are seeing numerous occasional buildfarm failures of the fk-deadlock2
> > isolation test,
>
> Yeah, I complained about this already, but Kevin disclaims all
> responsibility for the fk isolation tests. It looks like Alvaro
> and Noah Misch are the people to be harassing.
Yep; I took advantage of Kevin's test harness for some unrelated tests.
These sporadic failures happen whenever the test case takes longer than
deadlock_timeout (currently 100ms for these tests) to setup the deadlock. I
outlined some mitigating strategies here:
http://archives.postgresql.org/message-id/20110727171438.ge18...@tornado.leadboat.com
I'd vote for #1: let's double the deadlock_timeout until the failures stop.
Other opinions?
Thanks,
nm
*** a/src/test/isolation/specs/fk-deadlock.spec
--- b/src/test/isolation/specs/fk-deadlock.spec
***
*** 19,25 teardown
}
session "s1"
! setup { BEGIN; SET deadlock_timeout = '100ms'; }
step "s1i"{ INSERT INTO child VALUES (1, 1); }
step "s1u"{ UPDATE parent SET aux = 'bar'; }
step "s1c"{ COMMIT; }
--- 19,25
}
session "s1"
! setup { BEGIN; SET deadlock_timeout = '200ms'; }
step "s1i"{ INSERT INTO child VALUES (1, 1); }
step "s1u"{ UPDATE parent SET aux = 'bar'; }
step "s1c"{ COMMIT; }
*** a/src/test/isolation/specs/fk-deadlock2.spec
--- b/src/test/isolation/specs/fk-deadlock2.spec
***
*** 24,30 teardown
}
session "s1"
! setup { BEGIN; SET deadlock_timeout = '100ms'; }
step "s1u1" { UPDATE A SET Col1 = 1 WHERE AID = 1; }
step "s1u2" { UPDATE B SET Col2 = 1 WHERE BID = 2; }
step "s1c"{ COMMIT; }
--- 24,30
}
session "s1"
! setup { BEGIN; SET deadlock_timeout = '200ms'; }
step "s1u1" { UPDATE A SET Col1 = 1 WHERE AID = 1; }
step "s1u2" { UPDATE B SET Col2 = 1 WHERE BID = 2; }
step "s1c"{ COMMIT; }
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Re: [HACKERS] random isolation test failures
Andrew Dunstan writes: > We are seeing numerous occasional buildfarm failures of the fk-deadlock2 > isolation test, Yeah, I complained about this already, but Kevin disclaims all responsibility for the fk isolation tests. It looks like Alvaro and Noah Misch are the people to be harassing. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] random isolation test failures
Andrew Dunstan wrote: > We are seeing numerous occasional buildfarm failures of the > fk-deadlock2 isolation test > If this is harmless, we could provide an alternative results file > as a simple fix. If it's not harmless, it should be fixed. I agree, but don't look at me. I'm not the one who added the tests, nor are they related to serializable snapshot isolation. Tom recently raised the same issue on this thread: http://archives.postgresql.org/pgsql-hackers/2011-09/msg00991.php Alvaro? -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
