Kubernetes API Server: Architecture, Authentication, Authorization, and Debugging#

The API server (kube-apiserver) is the front door to your Kubernetes cluster. Every interaction – kubectl commands, controller reconciliation loops, kubelet status updates, admission webhooks – goes through the API server. It is the only component that reads from and writes to etcd. If the API server is down, the cluster is unmanageable. Everything else (scheduler, controllers, kubelets) can tolerate brief API server outages because they cache state locally, but no mutations happen until the API server is back.