Re: BUG #13657: Some kind of undetected deadlock between query and "startup process" on replica.

On Thu, Oct 1, 2015 at 9:52 PM, Maxim Boguk <maxim(dot)boguk(at)gmail(dot)com> wrote:
>> So wal replay got AccessExclusiveLock on relation 17987 and waiting for
>> something.
>> And query waiting for AccessShareLock on the same relation.
>>
> gdb backtrace from stuck startup process:
> (gdb) bt
> #0 0x00007f04ad862633 in select () from /lib/x86_64-linux-gnu/libc.so.6
> #1 0x00007f04af86488e in pg_usleep (microsec=<optimized out>) at
> /tmp/buildd/postgresql-9.4-9.4.4/build/../src/port/pgsleep.c:53
> #2 0x00007f04af7328ac in WaitExceedsMaxStandbyDelay () at
>
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/storage/ipc/standby.c:171
> #3 ResolveRecoveryConflictWithVirtualXIDs
> (reason=PROCSIG_RECOVERY_CONFLICT_SNAPSHOT, waitlist=0x7f04b13ba2f0) at
>
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/storage/ipc/standby.c:232
> #4 ResolveRecoveryConflictWithVirtualXIDs (waitlist=0x7f04b13ba2f0,
> reason=PROCSIG_RECOVERY_CONFLICT_SNAPSHOT) at
>
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/storage/ipc/standby.c:191
> #5 0x00007f04af544445 in heap_xlog_clean (record=0x7f04b1395b80,
> lsn=107351881751648) at
>
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/access/heap/heapam.c:7329

This backtrace is not indicating that this process is waiting on a relation
lock, it is resolving a recovery conflict while removing tuples, killing
the virtual transaction depending on if max_standby_streaming_delay or
max_standby_archive_delay are set if the conflict gets longer. Did you
change the default of those parameters, which is 30s, to -1? This would
mean that the standby waits indefinitely.
--
Michael