Debugging service connectivity in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Check pod connectivity with kubectl exec

You want to verify if a pod named webapp-1 can reach the service backend on port 8080. Which command will correctly test this connectivity?

A kubectl exec -it webapp-1 -- ping backend 8080

B kubectl exec webapp-1 curl backend:8080

C kubectl exec webapp-1 -- nc -z backend 8080

D kubectl exec webapp-1 -- curl backend:8080

💡 Hint

Remember to use the correct syntax for kubectl exec with commands.

Option D correctly uses kubectl exec with the pod name, the -- separator, and the command curl backend:8080 to test HTTP connectivity. Option D misses the -- separator, causing a syntax error. Option D uses ping with a port, which is invalid. Option D uses nc but nc may not be installed and the syntax is incomplete.

🧠 Conceptual

intermediate

Understanding Kubernetes Service Types

Which Kubernetes service type exposes the service on a cluster-internal IP only, making it reachable only from within the cluster?

A NodePort

B ClusterIP

C LoadBalancer

D ExternalName

💡 Hint

Think about which service type does not expose ports outside the cluster nodes.

ClusterIP exposes the service on an internal IP accessible only within the cluster. NodePort and LoadBalancer expose services externally. ExternalName maps to an external DNS name.

❓ Troubleshoot

advanced

Diagnosing DNS resolution failure inside a pod

A pod cannot resolve the service name database. Which command inside the pod will help verify if DNS resolution is working?

A nslookup database

B curl database

C ping -c 1 database

D dig database

💡 Hint

Use a command that queries DNS directly.

The nslookup command queries DNS and shows if the name resolves. curl tests HTTP but fails if DNS fails silently. ping may not be installed or blocked. dig is not always installed in minimal containers.

🔀 Workflow

advanced

Order the steps to debug a Kubernetes service connectivity issue

Put these steps in the correct order to debug why a pod cannot connect to a service:

A 1,2,3,4

B 2,1,3,4

C 3,1,2,4

D 1,3,2,4

💡 Hint

Start from DNS, then endpoints, then connectivity, then logs.

First verify DNS resolution (step 1), then check if the service has endpoints (step 2), then test actual connectivity (step 3), and finally check application logs (step 4).

✅ Best Practice

expert

Identify the cause of intermittent service connectivity failures

A Kubernetes service intermittently fails to connect to its pods. Which is the most likely cause?

A The service type is ClusterIP instead of NodePort.

B The pod's container image is outdated.

C Pods are crashing and restarting frequently causing endpoints to be temporarily missing.

D The cluster nodes have insufficient CPU resources.

💡 Hint

Think about what causes endpoints to disappear temporarily.

If pods crash and restart often, the service endpoints list changes, causing intermittent connectivity failures. Service type or image version does not cause intermittent connectivity. Insufficient CPU may cause slowness but not intermittent connection drops.