I have a Postgresql 9.1+134wheezy4 running on Debian 7 Wheezy. From 2015-02-07 on (I guess it has been backported then, see below) I regularly see the following line in /var/log/postgresql/postgresql-9.1-main.log:
2015-02-07 11:08:33 CET LOG: using stale statistics instead of current ones because stats collector is not responding
I shows a up few times a day, nothing spectacular or to worry about. But I don't get the meaning of the line and couldn't find documentation about it. It is mentioned in the changelogs for 9.3.6 and 9.4.1:
Change "pgstat wait timeout" warning message to be LOG level, and rephrase it to be more understandable (Tom Lane)
This message was originally thought to be essentially a can't-happen case, but it occurs often enough on our slower buildfarm members to be a nuisance. Reduce it to LOG level, and expend a bit more effort on the wording: it now reads "using stale statistics instead of current ones because stats collector is not responding".
Unfortunately, it does not explain the meaning. I also had WARNING: pgstat wait timeout until it changed in February as often as the new message. The information on the log line are also not helpful/constructive. A frequent advice is to restart the server or to remove the shared memory segment.
These are the logs for a postgresql restart:
2015-05-25 17:01:39 CEST LOG: using stale statistics instead of current ones because stats collector is not responding
2015-05-25 18:00:04 CEST LOG: received fast shutdown request
2015-05-25 18:00:04 CEST LOG: aborting any active transactions
2015-05-25 18:00:04 CEST LOG: autovacuum launcher shutting down
2015-05-25 18:00:04 CEST LOG: shutting down
2015-05-25 18:00:04 CEST LOG: database system is shut down
2015-05-25 18:00:06 CEST LOG: database system was shut down at 2015-05-25 18:00:04 CEST
2015-05-25 18:00:06 CEST LOG: database system is ready to accept connections
2015-05-25 18:00:06 CEST LOG: autovacuum launcher started
2015-05-25 18:00:07 CEST LOG: incomplete startup packet
Could it mean that the statistics collector is somehow broken or misconfigured? What is the reason for this behaviour and how can it be avoided?
