a cluster consists of at least one control plane and multiple worker machines called nodes. These control plane and node machines run the Kubernetes cluster orchestration system.

Control plane

The control plane runs the control plane processes, including the Kubernetes API server, scheduler, and core resource controllers. The lifecycle of the control plane is managed by GKE when you create or delete a cluster. This includes upgrades to the Kubernetes version running on the control plane, which GKE performs automatically, or manually at your request if you prefer to upgrade earlier than the automatic schedule.

Control plane and the Kubernetes API

The control plane is the unified endpoint for your cluster. You interact with the cluster through Kubernetes API calls, and the control plane runs the Kubernetes API Server process to handle those requests. You can make Kubernetes API calls directly via HTTP/gRPC, or indirectly, by running commands from the Kubernetes command-line client (kubectl) or by interacting with the UI in the Cloud Console.

The API server process is the hub for all communication for the cluster. All internal cluster processes (such as the cluster nodes, system and components, application controllers) act as clients of the API server; the API server is the single "source of truth" for the entire cluster.

 

Control plane and node interaction

The control plane decides what runs on all of the cluster's nodes. The control plane schedules workloads, like containerized applications, and manages the workloads' lifecycle, scaling, and upgrades. The control plane also manages network and storage resources for those workloads.

The control plane and nodes communicate using Kubernetes APIs.

 

 

 

Nodes

A cluster typically has one or more nodes, which are the worker machines that run your containerized applications and other workloads.

Each node is managed from the control plane, which receives updates on each node's self-reported status.

A node runs the services necessary to support the containers that make up your cluster's workloads. These include the runtime and the Kubernetes node agent (kubelet), which communicates with the control plane and is responsible for starting and running containers scheduled on the node.