Kubelet is not a control plane component, but it plays a key role in the operation of a Kubernetes cluster.

Kubelet is an agent that runs on every node in a Kubernetes cluster. It ensures that containers in pods are started and run according to their specifications. Kubelet continuously interacts with kube-apiserver to verify and maintain the state of nodes and containers. It is also responsible for starting control plane components.

Kubelet interactions

Kubelet interactions are shown in the architecture diagram of the control-plane-manager module.

Kubelet interacts with the following components:

  1. kubernetes-api-proxy: Proxies requests to kube-apiserver that are sent to the localhost address. It is part of the control-plane-manager module.
  2. kube-apiserver-healthcheck: Checks the health of kube-apiserver.

The following components interact with kubelet:

  1. kube-apiserver:

    • Retrieving pod logs (the kubectl logs command)
    • Executing commands in running pods (the kubectl exec command)
    • Port forwarding (the kubectl port-forward command)

  2. prometheus-main: Collects kubelet metrics.