Prometheus to get trigger an alert when node is in unschedulable state
If you use prometheus-operator, kube-state-metrics return kube_node_status_condition metric:
sum(kube_node_status_condition{condition="Ready",status!="true"})
The above answer would show if a node it ready or not - a node can be ready but unschedulable (an example would be if you cordoned a node with:
kubectl cordon NODE)Below example should cover a ready node that is unschedulable and is also available via kube-state-metrics
sum(kube_node_spec_unschedulable) by (node)
I'm referencing the machine_cpu_cores metric. It will only show nodes that are ready in a Kubernetes cluster.