Kubernetes Services

 Hello everyone !! In this post, we will discuss the Kubernetes Services, What, and How we can deploy the service on a Kubernetes cluster.

What is Kubernetes Service?

We have Kubernetes services for not to remember the pod IP address, it is more comfortable inter-connecting the pods using service names.

Why we need Kubernetes Services?

We will get to know once we deploy the following different kinds of Kubernetes services on your Kubernetes cluster.

Types of Kubernetes Services

• NodePort
• ClusterIP
• Headless 
• Loadbalancer

Kubernetes Service types

NodePort

The node port will be a port enabled on a Node per microservice application. 

Let's have pod defination in myapp.yaml

apiVersion: v1
kind: Pod
metadata:
    name: myapp-pod
    labels:
        app: myapp
spec:
    containers:
        - name: nginx-containers
          image: nginx

Create the myapp pod using the above defination.

Example nodeport.yaml file

apiVersion: v1
kind: Service
metadata:
  name: appservice
spec:
  type : NodePort
  ports:
    - port: 80
      targetPort: 80
      nodePort: 30008
  selector:
    app: myapp

kubectl create -f nodeport.yaml
kubctl get services
kubectl describe service appservice

ClusterIP 

- Headless services such as database services which are needed to be exposed to internal Kubernetes services like web application service.

apiVersion: v1
kind: Service
metadata:
  name: app-service
spec:
  ports:
    - port: 80
      protocol: TCP
  selector:
    app: app-server
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-server
  labels:
    app: app-server
spec:
  selector:
    matchLabels:
      app: app-server
  template:
    metadata:
      labels:
        app: app-server
    spec:
      containers:
      - name: web-server
        image: nginx
        ports:
        - containerPort: 80

Load balancer

You can configure a LoadBalancer on any of the Cloud provider. GCP, AWS OCI etc. 

Here in the below we will consider the example of LoadBalancer using AWS cloud ELB

apiVersion: v1
kind: Service
metadata:
  name: lb-service
  labels:
    app: lb-service
spec:
  type: NodePort
  ports:
  - port: 80
  selector:
    app: frontend

Now we have the frontend-deployment.yml file as :

apiVersion: apps/v1
kind: Deployment
metadata:
  name: frontend-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: frontend
  minReadySecond: 30
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
        maxUnavailable: 0
  template:
    metadata:
      labels:
        app: frontend
    spec:
      containers:
      - name: frontend-container
        image: nginx

Reference:

1. ExternalName service Stackoverflow Question