Certified Kubernetes Application Developer (CKAD) Practice Test

What is the purpose of a liveness probe?

1. To ensure a container is ready to receive requests

2. To check if a container is running and alive

3. To manage the scaling of a pod based on load

4. To monitor resource usage of a pod

The correct answer is: To check if a container is running and alive

A liveness probe is specifically designed to determine if a container within a pod is still running and 'alive' in the sense that it is functioning correctly. If a liveness probe fails, Kubernetes will automatically restart the container to restore it to a healthy state. This is critical for maintaining the stability and availability of applications running in a Kubernetes environment. This mechanism is essential for scenarios where a container may be running but is stuck in a state where it cannot process requests or perform its tasks, which may not necessarily be detected by other probes like readiness probes. Therefore, the correct identification of an application's operational status through a liveness probe helps ensure high availability by allowing for automatic recovery of malfunctioning containers. Understanding the purposes of other options is also beneficial. For instance, readiness probes ensure that a container is ready to accept traffic, managing how requests are routed during the startup phase of an application. Scaling concerns are not directly related to liveness probes; those are handled by Kubernetes' Horizontal Pod Autoscaler or similar mechanisms based on metrics like resource utilization or custom metrics. Monitoring resource usage pertains to tools and APIs that track the performance of pods rather than the health of individual containers.