Ok… so for me… this is the scenario… and my take on it.
What we have is (and dont laugh please… its not my setup) :
- 3 Nodes running 3.0.14, inside Docker containers (I know… why would you do that).
- 2 Nodes on 3.2.22 (as a part of my upgrade process)
We were getting that error ^ on the logs on the 3.2.22 nodes, but only when communicating to the 3.0.14 nodes. We did not get them between the 3.2.22 nodes.
Also, the 3.0.14 nodes did not report the error when communicating to teh 3.2.22 nodes. They just reported connection opens and closes.
I have deduced from this it is a version issue with the heartbeat. Thee errors happen every 30 secinds , like clockwork. Data gets through from Primary to secondaries Ok, so it is not affecting operations.
I tried installing the older version on teh new nodes, but hit an issue as I have stopped automatic upgrades. I suspect that would have fixed it… but then , for me, I would have hit it again as a part of a rolling update.
Consequently I am leaving it, as teh old nods will be disappearing soon.
Its a version issue between 3.0.14 and 3.2.22… unless it crops up again.
Hope this helps someone, as it may not be limited to these versuions… and also I am not 100% suere docker isn;t playing a part in this either… but thats going too.