What is NodePort and what functionality does it provide?

NodePort is a type of Service in Kubernetes that opens a port on each node of the cluster. Traffic sent to this port on any node is forwarded to the Pod(s) associated with this Service.

Functionality of NodePort:

• Behavior change: Provides external access to the service. Traffic from outside the cluster can reach the service through any node IP and the specified NodePort.
• Ports:
  • NodePort: Default range 30000-32767. Can be changed with cluster settings.
  • TargetPort: The port on the Pod to which traffic is forwarded.
  • Port: The port of the Service inside the cluster.

Port	Description	Usage
NodePort	Port open on each node	External access to the service
TargetPort	Port in the Pod	Forwarding traffic from Service to Pod
Port	Service port inside the cluster	Internal interaction between services

• Availability: The service is accessible via NodeIP:NodePort address from any node in the cluster.
• Restrictions:
  • Requires opening NodePort on each node.
  • Not suitable for production environment due to fixed port range and the need to know the node IP.
  • More difficult to scale compared to LoadBalancer or Ingress.

Example YAML for NodePort Service:

apiVersion: v1
kind: Service
metadata:
  name: my-nodeport-service
spec:
  type: NodePort
  selector:
    app: my-app # Selector for choosing Pods
  ports:
    - protocol: TCP
      port: 80 # Service port
      targetPort: 8080 # Port in Pod
      nodePort: 31000 # Specified NodePort (optional, will be chosen automatically if not)