Kubernetes Control Plane and Data Plane Concepts

Internal

• Kubernetes Concepts

Cluster

A Kubernetes cluster consists of a set of nodes. Of those, a small number are master nodes, which are collectively known as the control plane, and a potentially relatively larger number of worker nodes, which run the cluster's workload.

Node

A node is a Linux host that can run as a VM, a bare-metal device or an instance in a private or public cloud. A node can be a master or worker.

Control Plane

The control plane is the cluster's set of master nodes. The control plane exposes the API via the API Server and contains the cluster store, controller manager, scheduler and other management components. The control plane makes workload scheduling decisions, performs monitoring and responds to external and internal events.

Master Node

A master node is a collection of system services that manage the Kubernetes cluster. The master nodes are sometimes called heads or head nodes, and most often simply masters. Collectively, they represent the control plane. While it is possible to execute user workloads on the master node, this is generally not recommended.

HA Master Nodes

The recommended configuration includes 3 or 5 replicated masters.

Data Plane

The data plane is the cluster's set of worker nodes.

Worker Node

A worker node, most often referred simply as "node" (as opposite to master), is where the application services run. Collectively, the worker nodes make up the data plane. A worker node constantly watches for new work assignments.