Kubernetes Control Plane

When you deploy Kubernetes, you get a cluster. A Kubernetes cluster consists of a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node.

The worker node(s) host Pods which are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster.

Kubernetes components

1. API server
   Api server is the component of the control plane that exposes the Kubernetes API. The main implementation of the API server is the kube-apiserver which scales horizontally.
2. etcd
   Consistent and highly available key value store used to store all cluster data.
3. scheduler
   Watches for newly created Pods with no assigned node, and selects a node for them to run on.
4. controller manager
   Runs multiple controller processes. Logically each controller is a seperate process. But to reduce complexity they are run as a single process. These controllers include
   a. Node controller
   b. Replication controller
   c. Endpoints controller
   d. Service Account and Token controller
5. cloud controller manager
   The cloud controller manager lets you link your cluster into your cloud provider’s API, and separates out the components that interact with that cloud platform from components that just interact with your cluster.