Introducing Kubernetes runtime components

A Kubernetes cluster contains two types of nodes: master nodes and worker nodes. Master nodes manage the cluster, while the main purpose of worker nodes is to run the actual workload, for example, the containers we deploy in the cluster. Kubernetes is built up of a number of runtime components. The most important components are as follows:

• There are components that run on master nodes, constituting the control plane:
  • The API server, the entry point to the control plane. This exposes a RESTful API, which, for example, the Kubernetes CLI tool known as kubectl uses.
  • etcd, a highly available and distributed key-value store, used as a database for all cluster data.
  • A controller manager, which contains a number of controllers that continuously evaluate the desired state versus the current state for the objects defined in the etcd database. Whenever the desired or current state changes, a controller that&...