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Learn Kubernetes: A Deep Dive

Accessing Apps from Outside the Cluster

Explore how to access applications running in Kubernetes from outside the cluster using NodePort and LoadBalancer services. Understand the flow of external traffic to pods via cluster nodes and key limitations of these exposure methods, enabling you to manage external access effectively.

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NodePort Services

NodePort Services build on top of ClusterIP Services by adding a dedicated port on every cluster node that external clients can use. We call this dedicated port the NodePort.

The following YAML shows a NodePort Service called skippy.

YAML
apiVersion: v1
kind: Service
metadata:
  name: skippy           <<==== Registered with the internal cluster DNS (ClusterIP)
spec:
  type: NodePort         <<==== Service type
  ports:
  - port: 8080           <<==== ClusterIP port
    targetPort: 9000     <<==== Application port in container
    nodePort: 30050      <<==== External port on every cluster node (NodePort)
  selector:
    app: hello-world

Posting this to the cluster will create a ClusterIP Service with the usual internally routable IP and DNS name. It will also create port 30050 on every cluster node and map it back to the ClusterIP. ...