KCNA - Cloud Native Application Delivery - Section 3.5

Explain how a running cloud native application is inspected and debugged.

Reading logs and events, exec into a container, port-forwarding, ephemeral debug containers, and the difference between liveness, readiness and startup probes when diagnosing an unhealthy workload.

kubectl logskubectl execport-forwardephemeral containersliveness, readiness and startup probes

Practice question for this objective

Free sampleCloud Native Application Deliverymedium

A team keeps confusing two Kubernetes probe types. One probe decides whether a running container is healthy enough to keep, and when it fails repeatedly the kubelet restarts that container. The other probe decides whether a container is ready to receive traffic, and when it fails the container stays running but is removed from the Service endpoints. Which pairing correctly matches each behaviour to its probe?

  • AThe restart-on-failure behaviour is the liveness probe, and the remove-from-endpoints behaviour is the readiness probe. Correct
  • BThe restart-on-failure behaviour is the readiness probe, and the remove-from-endpoints behaviour is the liveness probe.
  • CThe restart-on-failure behaviour is the startup probe, and the remove-from-endpoints behaviour is the liveness probe.
  • DThe restart-on-failure behaviour is the readiness probe, and the remove-from-endpoints behaviour is the startup probe.
Distinguish liveness probes, which restart unhealthy containers, from readiness probes, which control Service endpoint membership. The kubelet acts differently per probe: a failed liveness probe triggers a container restart, whereas a failed readiness probe only causes the endpoint controller to drop the Pod from Service endpoints, so the container keeps running but stops receiving traffic.

Why A is correct: A failing liveness probe causes the kubelet to restart the container, while a failing readiness probe leaves the container running but pulls it out of the Service endpoints so it receives no traffic, which is exactly the described split.

Why B is wrong: This reverses the two probes, which is a common mix-up, because readiness never restarts a container and liveness never merely deregisters an endpoint.

Why C is wrong: The startup probe only gates when the other probes begin and does not itself remove endpoints, and liveness restarts rather than deregisters, so neither half matches.

Why D is wrong: Readiness does not restart containers and the startup probe governs initial start-up timing rather than endpoint membership, so both descriptions are attached to the wrong probe.

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