Probe failure and container restart behavior in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What happens when a liveness probe fails in Kubernetes?

In Kubernetes, if a liveness probe fails repeatedly, what is the expected behavior for the container?

A The container is restarted by the kubelet.

B The container is paused but not restarted.

C The pod is deleted and recreated by the scheduler.

D Nothing happens; the container continues running.

💡 Hint

Think about how Kubernetes ensures containers stay healthy.

A liveness probe failure signals Kubernetes that the container is unhealthy. Kubernetes restarts the container to try to fix the issue.

💻 Command Output

intermediate

Output of 'kubectl describe pod' after readiness probe failure

You run kubectl describe pod myapp and see the readiness probe failing repeatedly. What status will the pod show in the output?

A Pod status will be <strong>Succeeded</strong>.

B Pod status will be <strong>CrashLoopBackOff</strong>.

C Pod status will be <strong>Pending</strong>.

D Pod status will be <strong>Running</strong> but <em>Ready</em> condition will be <strong>False</strong>.

💡 Hint

Readiness probes affect traffic routing but not pod lifecycle.

When readiness probes fail, the pod stays running but is marked as not ready, so it won't receive traffic.

❓ Troubleshoot

advanced

Why does a container restart repeatedly despite a successful readiness probe?

A container restarts repeatedly, but its readiness probe always succeeds. What is the most likely cause?

A The pod resource limits are too high.

B The readiness probe failure causes restarts.

C The liveness probe is failing, causing restarts.

D The container image is missing.

💡 Hint

Readiness probes do not trigger restarts.

Liveness probe failures cause container restarts. Readiness probes only control traffic routing.

🔀 Workflow

advanced

Order of events when a liveness probe fails repeatedly

Arrange the following Kubernetes events in the correct order when a liveness probe fails repeatedly:

A 2,1,3,4

B 1,2,3,4

C 1,3,2,4

D 3,1,2,4

💡 Hint

Think about how Kubernetes handles unhealthy containers step-by-step.

The kubelet first detects the failure, then kills the container, restarts it, and updates pod status accordingly.

✅ Best Practice

expert

Choosing probe types to avoid unnecessary container restarts

You want to ensure your container restarts only when truly unhealthy, but you also want to control traffic routing carefully. Which probe configuration is best?

A Use a liveness probe that checks critical health and a readiness probe that checks service availability.

B Use only a readiness probe to control restarts and traffic.

C Use only a liveness probe for both restarts and traffic control.

D Disable both probes and rely on manual restarts.

💡 Hint

Consider the distinct roles of liveness and readiness probes.

Liveness probes trigger restarts on failure, readiness probes control traffic routing without restarts. Using both properly avoids unnecessary restarts.