Scenario

In namespace disco, the application discovery-app relies on DNS-based discovery of peer pods. The service discovery-svc is supposed to return all backend pod IPs, but currently:

kubectl exec deploy/testpod -n disco -- nslookup discovery-svc.disco.svc.cluster.local

returns only one IP instead of individual pod IPs. The application cannot discover its peers and fails to form a cluster.

Task

Fix the service configuration so that DNS resolution of discovery-svc returns one IP per pod, allowing the application to discover all running instances.

Step 1: Verify the issue

kubectl exec deploy/testpod -n disco -- nslookup discovery-svc.disco.svc.cluster.local

Returns only one IP (the ClusterIP), not individual pod IPs.

Step 2: Check current service configuration

kubectl get svc discovery-svc -n disco -o yaml

Notice it has a clusterIP assigned (e.g., 10.43.x.x). This is a regular service that load-balances to pods but DNS only returns the single ClusterIP.

Step 3: Understand the fix

For DNS to return individual pod IPs, the service must be headless (clusterIP: None). A headless service:

• Has no cluster IP
• DNS returns A records for each pod IP directly
• Used for stateful apps, peer discovery, and direct pod addressing

Step 4: Export and modify the service

kubectl get svc discovery-svc -n disco -o yaml > discovery-svc.yaml

Edit the file discovery-svc.yaml:

Change clusterIP to None and remove already existing clusterIPs

apiVersion: v1
kind: Service
metadata:
  name: discovery-svc
  namespace: disco
spec:
  clusterIP: None    # Changed from assigned IP to None
  selector:
    app: discovery
  ports:
  - port: 80
    targetPort: 80

Step 5: Delete and recreate the service

kubectl delete svc discovery-svc -n disco
kubectl apply -f discovery-svc.yaml

Note: clusterIP cannot be changed on an existing service - must delete and recreate.

Step 6: Verify DNS returns multiple IPs

kubectl exec deploy/testpod -n disco -- nslookup discovery-svc.disco.svc.cluster.local

Should now return 3 IP addresses (one per pod).