Understanding Kubernetes Node Types: Worker, Control Plane, and Edge Nodes

Kubernetes nodes are the machines that run applications and tasks in a cluster. Each node runs essential components such as kubelet, kube-proxy, a container runtime, and network plugins, and communicates with the master (control plane) via the Kubernetes API server.

Node roles include:

Worker node: Executes application workloads.

Control Plane node: Maintains cluster state, schedules pods, and handles networking.

Edge node: Operates at the network edge to communicate with external networks.

All nodes must register with the control plane and provide sufficient CPU, memory, and storage resources.

Worker Node Overview

A Worker node is the most common node type, running components like kubelet, a container runtime (e.g., Docker), and network plugins. The control plane assigns pods to workers, and each worker must have enough resources and a compatible runtime.

Example commands:

gcloud compute instances create worker-node --machine-type n1-standard-1 --zone us-central1-a

Creating a Pod on a Worker node:

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: my-container
    image: nginx:latest

Creating a PersistentVolumeClaim (PVC):

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1Gi

Running a Job on a Worker node:

apiVersion: batch/v1
kind: Job
metadata:
  name: hello-world
spec:
  completions: 1
  parallelism: 1
  template:
    spec:
      containers:
      - name: hello-world
        image: busybox
        command: ["/bin/sh", "-c", "echo Hello, World!"]
      restartPolicy: Never

Control Plane Node Overview

The Control Plane node runs critical components such as kube-apiserver, etcd, kube-scheduler, and kube-controller-manager to maintain cluster state and schedule workloads. Typically a cluster has at least one control plane node, with multiple nodes for high availability.

Example command to create a Deployment from the control plane:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: nginx:latest

Viewing cluster resources:

kubectl get all

Adding a new Worker node to the cluster:

gcloud container clusters add-node cluster-name --zone us-central1-a --num-nodes=1

Marking a node as unschedulable for maintenance:

kubectl drain node-name

Edge Node Overview

An Edge node is a specialized Worker node positioned at the network edge to handle external traffic. It can serve as an Edge Gateway, Edge Router, Edge Firewall, or Edge CDN, providing security, routing, and caching functions.

Example command to create an Edge Gateway node:

gcloud compute instances create edge-gateway --machine-type n1-standard-1 --zone us-central1-a

Configuring an edge service:

kubectl edit svc/my-service

Setting up a firewall rule for the edge node:

gcloud compute firewall-rules create allow-http --allow tcp:80 --target-tags=edge-node --source-ranges=0.0.0.0/0

Deploying an edge cache:

kubectl run my-cache --image=nginx --expose=true --port=80
kubectl proxy