Demo - Users App deployed on Kubernetes

Simple Users Spring Boot deployment on Minikube

Prerequisites

- Install VirtualBox from https://www.virtualbox.org/wiki/Downloads	
- Install Minikube from https://kubernetes.io/docs/tasks/tools/install-minikube/ 
- Install kubectl from https://kubernetes.io/docs/tasks/tools/install-kubectl/

Create and run a simple Spring Boot app

1 - To create a simple app go to Spring initializr and then add the following dependencies: web, actuator, jpa, rest, hsqldb and lombok.

Alternatively, you can do the following

# curl https://start.spring.io/hello.zip -d bootVersion=1.5.9.RELEASE \
     -d dependencies=web, actuator, jpa, rest, hsqldb, lombok \
     -d groupId=com.ssense.k8s -d artifactId=users \
     -d name=user -d baseDir=user -o user.zip
#unzip user.zip
#cd user

2 - Once you create the endpoints you need on Spring Boot, you need to add a property enabling the /application/env endpoint. This allows us to inspect environment variables added by Kubernetes.

src/main/resources/application.properties

endpoints.env.enabled=true

Also we need to add in the same file the in-memory db connection properties

spring.datasource.url=jdbc:hsqldb:file:target/testdb
spring.datasource.username=sa
spring.jpa.hibernate.ddl-auto=create
spring.datasource.initialize=true

3 - Create a Dockerfile so we can package this app as a Docker image

Dockerfile

 #the parent image
 FROM openjdk:8
 
 # the volume where your docker image will be saved locally
 VOLUME /tmp
 
 # copy your app into the container
 ADD ./target/users-0.0.1-SNAPSHOT.jar /users.jar
 
 
 RUN sh -c 'touch /users.jar'
 
 # allows to configure a container that will run as an executable
 ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/users.jar"]

The Dockerfile will define what goes on the environment inside your container.

4 - start Docker. Start the virtualBox and the minikube with a local Kubernetes cluster

minikube start

5 - Build the app and the Docker image. Note: we share the Docker environment used by Minikube, so we can communicate with the built-in Docker inside the Minikube

eval $(minikube docker-env)
./mvnw clean package
docker build -t $USER/users:0.0.1 .

One you create the image you can check where your image is with

docker images

6 - Now we run a Kubernetes deployment on the running Minikube cluster

kubectl run users --image $USER/users:0.0.1 --port 8080
kubectl expose deployment users --type=NodePort

7 - Our service now run on the Minikube cluster, let's find out the IP address for the minikube and the external port for our service.

minikube service users --url
kubectl get service users
kubectl describe services users

And if you need to check the pods deployed

kubectl get pods

Now if you need to scale up your application (the sales are coming??), we add 4 more pods (5 total)

kubectl scale deployment users --replicas=5
kubectl get pods

Finally if you need to update your deployed image, build a new version of the application, create the new image and update it in Kubernetes:

docker build -t $USER/users:0.0.2 .
kubectl set image deployment/users users=users:0.0.2

Clean everything

 kubectl delete all -l run=users
 minikube stop