we are running many postgresql master/slave setups. The slaves are initialised
from a pg_basebackup from the master and are sync streaming from the master.
When we determine the master has failed, the slave is promoted. Some time after
that, the old master is again initialised with a pg_basebackup and starts
streaming from the new master.
Our setup seems pretty "stock" and has been running for us for some years (with
different versions of postgresql but also different OSes).
Recently, we have gotten this error a fair amount of times: "out-of-order XID
insertion in KnownAssignedXids" when postgresql attempts to start after being
initialised with a pg_basebackup from the current master.
The only reference I can find on that particular error, is from 2012 and the
resulting issue is long fixed in our version of postgresql (9.5.3) ...
Once the issue has occurred, a subsequent re-initialisation (with a completely
new pg_basebackup) does not resolve the issue.
I have a setup in the failing state, so I can produce any kind of log mesages /
details that would be helpful.
Thank you for your support,