Guys, still need your help. Previous night: *2019-04-05 00:35:04 UTC LOG: could not truncate directory "pg_serial": apparent wraparound* *2019-04-05 00:40:04 UTC LOG: could not truncate directory "pg_serial": apparent wraparound* (2 checkpoints)
It turned that I have some problem with performance related to predicate locking on this platform. A lot of long prepared statements with the *SerializableXactHashLock* and *predicate_lock_manager* wait_events followed by high CPU usage happened during 00:30 and 00:45. During this period there were 55k pred locks granted at max and 30k in average. Probably because of high CPU usage some statements were spending a lot of time in bind/parse steps. Probably if you advise me what could cause *"pg_serial": apparent wraparound* messages I would have more chances to handle all the performance issues. Thank you! -- Pavel Suderevsky E: psuderev...@gmail.com пн, 11 мар. 2019 г. в 19:09, Pavel Suderevsky <psuderev...@gmail.com>: > Hi, > > PG: 9.6.11 > OS: CentOS > Env: AWS EC2 > > I've faced the following exceptions in PostgreSQL server log: > > could not truncate directory "pg_serial": apparent wraparound > Sometimes it repeats every 5 min and the longest period was 40 min. > > In fact, I can't find any suspicious events happening that periods. > pg_wait_sampling didn't catch any events, no long queries (more than 60s), > Autovacuum workers or transactions in "idle in transaction" state were in > action at this time. > > The only related I could find in archive is: > https://www.postgresql.org/message-id/CACjxUsON4Vya3a6r%3DubwmN-4qTDDfZjuwSzjnL1QjdUc8_gzLw%40mail.gmail.com > >You should not see the errors you are reporting nor > >the warning I mentioned unless a serializable transaction remains > >active long enough for about 1 billion transaction IDs to be > >consumed. > > Database age now is just 18.5 millions of transactions. > > Server has two standbys (sync and async), hot_standby_feedback is off. > > Please advice what I can do to find a reason of these exceptions. >
