How to Expose an App in Kubernetes to the Internet

One of the features that Kubernetes provides is "service discovery and load balancing". Kubernetes can expose a container using the DNS name or using their own IP address. If traffic to a container is high, Kubernetes is able to load-balance and distribute the network traffic so that the deployment is stable.

This article shows how to create a Kubernetes Service object that exposes an external IP address.

Before you begin

• Install kubectl
• Use a Kubernetes control plane such as that provided by AWS's Elastic Kubernetes Service
• Configure kubectl to communicate with your Kubernetes API server

Objectives

• Run five instances of a Hello World application
• Create a Service object that exposes an external IP address
• Use the Service object to access the running application

Run five instances of a Hello World application

Run a Hello World application in your cluster by creating the following deployment file (load-balancer-example.yaml)

apiVersion: apps/v1
? ?
kind: Deployment
? ?
metadata:
? ?
? labels:
? ?
? ? app.kubernetes.io/name: load-balancer-example
? ?
? name: hello-world
? ?
spec:
? ?
? replicas: 5
? ?
? selector:
? ?
? ? matchLabels:
? ?
? ? ? app.kubernetes.io/name: load-balancer-example
? ?
? template:
? ?
? ? metadata:
? ?
? ? ? labels:
? ?
? ? ? ? app.kubernetes.io/name: load-balancer-example
? ?
? ? spec:
? ?
? ? ? containers:
? ?
? ? ? - image: gcr.io/google-samples/node-hello:1.0
? ?
? ? ? ? name: hello-world
? ?
? ? ? ? ports:
? ?
? ? ? ? - containerPort: 8080

        

The proceeding command creates a Deployment and an associated ReplicaSet. The ReplicaSet has five Pods each of which runs the Hello World application.

kubectl apply -f load-balancer-example.yaml        

Display information about the deployment

kubectl get deployments hello-world 

kubectl describe deployments hello-world        

Display information about your ReplicaSet objects

kubectl get replicasets

kubectl describe replicasets        

Create a Service object that exposes the deployment

The proceeding command will create a Service object that exposes Hello World application for access from the Internet. It will declaratively provision a classic load balancer within your AWS account.

kubectl expose deployment hello-world --type=LoadBalancer --name=my-service        

Display information about the Service using the proceeding commands

kubectl get services my-service

kubectl describe services my-service        

Make notes of the LoadBalancer Ingress's DNS name and the value of the Port and NodePort exposed by the Service. Use the DNS address and port number to access the Hello World application.

curl https://ae5cb07ebfaf14fb283c20d988a0da90-1987687362.eu-west-1.elb.amazonaws.com:8080        

The response to a successful request is a hello message:

Hello Kubernetes!        

Cleaning up

To delete the Service, enter this command:

kubectl delete services my-service        

To delete the Deployment, the ReplicaSet, and the Pods that are running the Hello World application, enter this command:

kubectl delete deployment hello-world        

What's next

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