7/20/2021

Simple SpringBoot Application Deployment In Kubernetes

The purpose of this blog post is to explain how to deploy simple spring boot application inside Kubernetes cluster and access rest services which exposed by those applications.

Please note this is not my own creation but inspired by another blog post.

Also I am using minikube as single node Kubernetes cluster and you can follow below official document to learn more about it.

https://minikube.sigs.k8s.io/docs/

Steps to follow

Start minikube

$ minikube start

Open minikube tunnel in another terminal to enable access k8s services out side the cluster

$ minikube tunnel

Clone SpringBoot repository

https://github.com/dhanuka84/tutorials.git

cd ./tutorials/spring-cloud/spring-cloud-kubernetes/kubernetes-minikube

Building demo-backend app & Docker image

cd ./demo-backend

mvn package spring-boot:repackage

# this is important otherwise k8s cluster can't pull the docker image

eval $(minikube docker-env)

docker build --file=Dockerfile --tag=demo-backend:latest --rm=true .

Building demo-frontend app & Docker image

/kubernetes-minikube/demo-frontend$ mvn package spring-boot:repackage

docker build --file=Dockerfile --tag=demo-frontend:latest --rm=true .

Deploy backend and frontend applications

kubectl create deploy demo-backend --image=demo-backend:latest --port=8080 --replicas=3 --dry-run=client -o yaml > deploy.yml

vi deploy.yml

We need to change the image pull policy to Never in deployment (line: 22). Please refer below document for more details.

https://kubernetes.io/docs/concepts/configuration/overview/

kubectl apply -f deploy.yml

kubectl create deploy demo-frontend --image=demo-frontend:latest --port=8081 --replicas=3 --dry-run=client -o yaml > frontend.yml

Edit image pull policy as below and deploy

kubectl apply -f frontend.yml

Expose both frontend and backend deployments/apps

dhanuka@dhanuka:~/kubernetes-minikube$ kubectl expose deploy demo-backend

service/demo-backend exposed

dhanuka@dhanuka:~/kubernetes-minikube$ kubectl expose deploy demo-frontend --type=NodePort

service/demo-frontend exposed #Get the node_ip and node_port for external access for front-end service

dhanuka@dhanuka:~/kubernetes-minikube$ minikube service --url demo-frontend

http://192.168.49.2:32143

Access the backend through frontend

Explaining with SpringBoot application.

Backend application expose a rest API with server port 8080 and return a message with "Hello from " prefix and pod name.

Frontend application expose an rest API with server port 8081 and return a message with "Message from backend is: " prefix plus message getting from Backend service.

So when we access the front end service with node_ip and node_port as below we will get the message as below.