Kcna Kubernetes And Cloud Native Associate · Free Practice Question Medium
Question 49
You are troubleshooting an issue in your Kubernetes cluster where worker nodes are intermittently unable to communicate with the control plane. You suspect an issue with the Kubernetes API server, as some components of the control plane are becoming unreachable. The cluster consists of three master nodes in an HA configuration, and each node is configured with an etcd database. Which of the following could most likely explain the intermittent communication issues between the worker nodes and the control plane?
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A
The container runtime on the worker nodes is causing the API server to crash.
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B
The etcd cluster is out of sync across the master nodes.
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C
The kube-scheduler is misconfigured and causing delays in Pod scheduling.
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D
The kubelet on each worker node is not communicating with the API server due to firewall restrictions.
Reveal correct answer
Correct answer: D
A.
While the container runtime is essential for running containers, issues with it would affect the ability to run workloads on the worker nodes, not the communication between the API server and worker nodes. Additionally, a failing container runtime on the worker nodes wouldn’t crash the API server on the master nodes; these are separate components with different roles.
B.
While etcd is a critical component of the control plane, an out-of-sync etcd cluster would affect the consistency of the data stored in etcd (like the current state of the cluster), but it would not directly cause communication failures between the worker nodes and the API server. More severe etcd issues could lead to broader control plane failures, but the question describes intermittent issues.
C.
The kube-scheduler is responsible for assigning Pods to nodes based on available resources, but it does not handle network communication between worker nodes and the API server. Misconfiguration here would impact Pod scheduling, but it wouldn’t lead to communication failures between the API server and worker nodes.
D.
The kubelet is responsible for communicating with the API server to receive instructions on managing Pods and maintaining node health. If communication is intermittently failing, it is likely that network or firewall issues are preventing the kubelet on the worker nodes from reaching the API server. Ensuring that all necessary ports are open between the kubelet and the API server is crucial for cluster health.
Discussion
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