06-Services.md

Services

A service is a grouping of pods that are running on a cluster lables should be same for the respective pods and services

Types of services

• NodePort
• LoadBalancer
• ClusterIP

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NodePort

• exposes our webapp to the outside world

• let us assume we have deployment app and if we want to expose the app to outside world than we need a service of type NodePort.
• nodeport range 30000-32767

nodeport is the port on the node itself port refers to the port on service targetport refers to the port on the target container where actual app is running

Downsides of NodePort

1. you can only have once service per port
2. You can only use ports 30000 - 32767
3. If your node/VM IP address change, you need to deal with that

Create the deployment file nginx-deploy.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx-app
specs:
  replicas: 1
  selector:
    matchLabels:
      app: nginx-app
  template:
    metadata:
    labels:
      app: nginx-app
    specs:
      containers:
      - name: nginx-container
        image: nginx:1.7.9
        ports:
        - containerPort: 80

Create the Nodeport service file nginx-svc-np.yml

apiVersion: v1
kind: Service
metadata:
  name: my-service
  labels:
    app: nginx-app
spec:
  selector:
    app:nginx-app
  type: NodePort
  ports:
    - nodePort: 31000
      port: 80
      targetPort: 80

In service manifest file the selector section should be same as the pod label section

Create the deployment file

• kubectl create -f nginx-deploy.yml

  Create the nodeport service

  • kubectl create -f nginx-svc-np.yml

  To display the service

  • kubectl get service -l app=nginx-app

  To get complete details about the service

  • kubectl describe svc my-service

  Now we can access the app using:

  1. Pod IP
  • kubectl get pod -o wide

  we will get the pod ip address here . so use curl http://pod_IP:targetport

  2. Using service IP
  • kubectl get svc -l app=nginx-app

  we will get the service ip and the service port so use curl http://Service_IP:port_number

  3. Using Node IP (external IP) Find the external ip of node on which the pod is running
  • kubctl get pod -o wide (to check where the pod is running)

Find the nodeport assigned to the service kubectl describe svc -l app=nginx-app

open in any browser NodeIP:NodePort/

To delete the files created we can simply delete the service we created and it will delete all the files related to that service

• kubectl delete svc my-service

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LoadBalancer