Affects Version/s: None
Fix Version/s: None
We had this scenario on an active NN machine.
- Disk array controller firmware has a bug. So disks stop working.
- ZKFC and NN still considered the node healthy; Communications between ZKFC and ZK as well as ZKFC and NN are good.
- The machine can be pinged.
- The machine can't be sshed.
So all clients and DNs can't use the NN. But ZKFC and NN still consider the node healthy.
The question is how we can have ZKFC and NN detect such OS/HW specific issues quickly? Some ideas we discussed briefly,
- Have other machines help to make the decision whether the NN is actually healthy. Then you have to figure out to make the decision accurate in the case of network issue, etc.
- Run OS/HW health check script external to ZKFC/NN on the same machine. If it detects disk or other issues, it can reboot the machine for example.
- Run OS/HW health check script inside ZKFC/NN. For example NN's HAServiceProtocol#monitorHealth can be modified to call such health check script.