I just found a few of these errors in a log file during some pgbench
testing tonight. Linux, recent CVS HEAD; given the range of systems and
versions this has been reported against now, this bug doesn't look like
a platform or version/build specific issue.
Unfortunately the instance I had up wasn't setup very well for logging,
but I did notice that all of the ones I saw had nearby messages about
autovacuum issues, which seems to match Tom's earlier suggestion at
http://archives.postgresql.org/pgsql-bugs/2009-07/msg00083.php that the
source of the warning (but not necessarily the underlying problem) for
these is the autovacuum launcher complaining; here's two different sets:
ERROR: canceling autovacuum task
CONTEXT: automatic analyze of table "pgbench.public.pgbench_accounts"
WARNING: pgstat wait timeout
WARNING: pgstat wait timeout
ERROR: canceling autovacuum task
CONTEXT: automatic analyze of table "pgbench.public.pgbench_accounts"
WARNING: pgstat wait timeout
ERROR: canceling autovacuum task
CONTEXT: automatic analyze of table "pgbench.public.pgbench_accounts"
ERROR: canceling autovacuum task
CONTEXT: automatic analyze of table "pgbench.public.pgbench_accounts"
Because of what I'm (not) seeing in pg_stat_bgwriter, I'm suspicious
that its underlying work or messages may be involved here. I'm not
seeing the sort of totals I expect in that view after these large bouts
of activity. Now, my use tonight has included the new
pg_stat_reset_shared('bgwriter') to clear out those stats between runs,
so perhaps that's involved too. Guessing not only because of the
reports going back to 8.4 that also have this error message.
Will keep an eye out for this one now that I know I might run into it,
have already cranked up the logging and will look for something
reproducible to gather more info.
--
Greg Smith 2ndQuadrant Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com www.2ndQuadrant.com