Error: ExternaName not working In Kubernetes

Symptom:

   We have ExternName for our DB service: test-db-svc:

apiVersion: v1
kind: Service
metadata:
  name: test-db-svc
  namespace: test-stage-ns
spec:
  externalName: 10.10.10.10
  ports:
  - port: 1521
    protocol: TCP
    targetPort: 1521
  sessionAffinity: None
  type: ExternalName

   After we upgrade Kubernetes Master nodes, DNS service stops resolving the ExternalName

 curl -v telnet://test-db-svc:1521
* Could not resolve host: test-db-svc; Name or service not known
* Closing connection 0curl: 
(6) Could not resolve host: test-db-svc; Name or service not known

Solution:

   It is due to the new version of Kubernetes doesn't support IP address on ExternalName. We need to replace it with FQDN

apiVersion: v1
kind: Service
metadata:
  name: test-db-svc
  namespace: test-stage-ns
spec:
  externalName: testdb.testdomain.com
  ports:
  - port: 1521
    protocol: TCP
    targetPort: 1521
  sessionAffinity: None
  type: ExternalName