Alert ClusterVersionOperatorDown is firing on OpenShift Container Platform 4

Issue

• We are receiving the below alert in one of our OCP 4 clusters. Although the cluster-version-operator pod is up and running:

  Alert details (rated as a P2)
  alert: ClusterVersionOperatorDown
  expr: absent(up{job="cluster-version-operator"} == 1)
  for: 10m
  labels:
    severity: critical
  annotations:
    message: Cluster version operator has disappeared from Prometheus target discovery. Operator may be down or disabled, cluster will not be kept up to date and upgrades will not be possible.