| 1 | This is the punchline drawing. Every component on the left — kubectl clients, the scheduler, the controller-manager, every kubelet on every node, kube-proxy, and the cloud-controller-manager — talks to one component in the middle, kube-apiserver. On the right, the apiserver is the only thing that writes to etcd, the cluster's sole persistent store. The arrows in green going back left are status reports and decisions; the arrows in cyan going right are watches and patches. This pattern — everything is API-mediated — is what makes Kubernetes pluggable, observable, and auditable. You can join the cluster by writing a controller that watches the API, and everything else falls into place. |