Auto-Scaling is OFF and Cluster-Upgrade is OFF but still dont know why cluster get restarted today morning. All Nodes got replace/change and All Pods got restarted
Reason is that it got restarted due to node got upgrade from 1.22 to 1.23 version
I have Regular Version in GKE Cluster
You should double-check with Google support (if you have a support plan), but I know from painful experience that if you're running a version of GKE that falls out of support, they may force-upgrade you to keep you within support, even if you have cluster upgrade turned off -- unless you use a maintenance exclusion.
The REGULAR channel release notes are here: https://cloud.google.com/kubernetes-engine/docs/release-notes-regular
The December 5th one is probably the one that affected you.
If you disable node auto-upgrade, you are responsible for ensuring that the cluster's nodes run a version compatible with the cluster's version, and that the version adheres to the Kubernetes version and version skew support policy.
Nodes running versions that have reached their end of life date are auto-upgraded even when auto-upgrade is disabled, to ensure supportability and version skew compatibility.
For more information you can read this link.
You can also check this link for temporary mitigation.
