k8service

Kubernetes Services Explained - ClusterIP vs NodePort vs Loadbalancer vs External

Pre-requisite for Kind cluster

If you use a Kind cluster, you must perform the port mapping to expose the container port. Use the below config to create a new Kind cluster

kind: Cluster

apiVersion: kind.x-k8s.io/v1alpha4

nodes:

- role: control-plane

  extraPortMappings:

  - containerPort: 30001

    hostPort: 30001

- role: worker

- role: worker

What is Service in Kubernetes

Different applications communicate with each other within Kubernetes using a service; it is also used to access applications outside the cluster.

There are 4 types of Services:

ClusterIP(For Internal access)

NodePort(To access the application on a particular port)

LoadBalancer(To access the application on a domain name or IP address without using the port number)

External (To use an external DNS for routing)

ClusterIP

Sample YAML for ClusterIP

apiVersion: v1

kind: Service

metadata:

  name: cluster-svc

  labels:

    env: demo

spec:

  ports:

  - port: 80

  selector:

    env: demo

NodePort

Sample YAML for Nodeport

apiVersion: v1

kind: Service

metadata:

  name: nodeport-svc

  labels:

    env: demo

spec:

  type: NodePort

  ports:

  - nodePort: 30001

    port: 80

    targetPort: 80

  selector:

    env: demo

LoadBalancer

Your loadbalancer service will act as nodeport if you are not using any managed cloud Kubernetes such as GKE,AKS,EKS etc. In a managed cloud environment, Kubernetes creates a load balancer within the cloud project, which redirects the traffic to the Kubernetes Loadbalancer service.

Sample YAML for Loadbalancer

apiVersion: v1

kind: Service

metadata:

  name: lb-svc

  labels:

    env: demo

spec:

  type: LoadBalancer

  ports:

  - port: 80

  selector:

    env: demo

Create Pod:

apiVersion: apps/v1

kind: Deployment

metadata:

  name: nginx-deploy

  labels:

    env: demo

spec:

  replicas: 3

  selector:

    matchLabels:

      env: demo

  template:

    metadata:

      labels:

        env: demo

      name: nginx  

    spec:

      containers:

      - name: nginx

        image: nginx

        ports:

        - containerPort: 80