Interview › Kubernetes, Docker, Helm & Podman
What happens when a liveness probe fails versus when a readiness probe fails?
Kubernetes, Docker, Helm & Podman · Basic level
Answer
When liveness fails, kubelet restarts the container. When readiness fails, Kubernetes removes the Pod from Service endpoints but does not restart it, which is useful when the process is alive but temporarily not able to serve traffic.
Technical explanation
Readiness failure is traffic control, while liveness failure is process recovery; mixing them up causes unnecessary restarts or bad traffic routing.
External dependencies are often appropriate for readiness but risky for liveness because a downstream outage can cause restart storms.
Health and resources are production controls, not just YAML fields; wrong settings cause outages, noisy restarts, bad rollouts, or wasted capacity.
Requests affect scheduling and node capacity planning; readiness affects traffic; liveness affects restart behavior.
Validate settings with real load, startup timing, memory profiles, and deployment rollout behavior.
Hands-on example
1. Create a namespace and deploy a small HTTP app specifically to test: force readiness failure and liveness failure separately to compare behavior.
2. Add probes and resources in YAML, then run kubectl describe pod, kubectl top pod, and kubectl rollout status to observe behavior.
3. Introduce a controlled failure such as slow startup, bad health endpoint, CPU load, or memory spike.
4. Tune thresholds, requests, and limits until rollout and runtime behavior are stable, then document the production values and why.
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More Kubernetes, Docker, Helm & Podman interview questions
- What is Kubernetes, and what problem does it solve over running containers manually?
- Explain the Kubernetes control plane components (API server, etcd, scheduler, controller manager).
- What runs on a worker node (kubelet, kube-proxy, container runtime)?
- What is a Pod, and why does Kubernetes schedule Pods rather than containers?
- What is the difference between a Pod, a ReplicaSet, and a Deployment?
- How does a Deployment perform a rolling update, and how do maxSurge and maxUnavailable work?
- How do you roll back a Deployment, and how does Kubernetes track revisions?
- What is a Service, and what are the types (ClusterIP, NodePort, LoadBalancer, ExternalName)?