KubeNodeUnschedulableCritical #

Meaning #

At least one Kubernetes node is marked as unschedulable for 24 hours.

This can be an intended situation, but often indicates that something is blocking an update.

Impact #

When Nodes are marked as unschedulable for an extended period of time, workloads can not get scheduled on them, reducing the resiliency of the cluster.

Diagnosis #

Find the unscheduable Node:

kubectl get nodes

Check taints and events:

kubectl describe nodes <relevant node>

check for blocking PodDisruptionBudgets:

kubectl get pdb --all-namespaces

Mitigation #

Resolve the problem blocking workload that. Most likely there is some draining not going through due to a blocking PodDisruptionBudget.