Control plane components (API server, scheduler, controller manager, etcd) in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Role of the Kubernetes API Server

Which statement best describes the primary role of the Kubernetes API server in the control plane?

A It stores all cluster data and state persistently.

B It schedules pods onto nodes based on resource availability.

C It acts as the central management point that exposes the Kubernetes API and processes REST requests.

D It manages the lifecycle of pods and nodes by running controllers.

💡 Hint

Think about which component handles communication and API requests in Kubernetes.

The API server is the central hub that exposes the Kubernetes API and processes REST requests from users and components.

💻 Command Output

intermediate

Output of etcdctl get Command

What is the expected output of the following command if the key 'config/version' exists with value 'v1.20.0' in etcd? etcdctl get config/version

Kubernetes

etcdctl get config/version

A config/version

B

config/version
v1.20.0

C Error: key not found

D v1.20.0

💡 Hint

Remember etcdctl outputs the key and value by default.

By default, etcdctl get outputs the key on one line and the value on the next line.

🔀 Workflow

advanced

Order of Control Plane Components Processing a Pod Creation

Arrange the order in which the Kubernetes control plane components process a pod creation request.

A 1,2,4,3

B 1,2,3,4

C 1,3,2,4

D 1,4,2,3

💡 Hint

Think about when the state is saved and when scheduling happens.

The API server first receives the request and stores it in etcd. Then the scheduler assigns the pod to a node, and finally the controller manager manages the pod lifecycle.

❓ Troubleshoot

advanced

Identifying the Cause of Pod Scheduling Failure

A pod remains in Pending state indefinitely. Which control plane component is most likely responsible for this issue?

A Scheduler is not running or unable to assign the pod to a node.

B API Server is down, so pod creation requests are not processed.

C Controller Manager failed to create the pod on the node.

D etcd has lost cluster state data for the pod.

💡 Hint

Consider which component decides where pods run.

The scheduler assigns pods to nodes. If it is down or stuck, pods remain Pending.

✅ Best Practice

expert

Ensuring High Availability of etcd in Kubernetes

What is the best practice to ensure high availability and data consistency of etcd in a Kubernetes cluster?

A Deploy an odd number of etcd instances in a cluster with quorum-based consensus.

B Run a single etcd instance on the master node with frequent backups.

C Use multiple etcd instances but allow them to run independently without synchronization.

D Store etcd data on local disks of worker nodes for faster access.

💡 Hint

Think about how distributed systems maintain consistency and availability.

Running an odd number of etcd instances in a cluster ensures quorum-based consensus, providing high availability and consistency.