Deploying Spring Boot and MongoDB as Containers Using Kubernetes and Docker

For this tutorial, you'll have a Dockerized sample spring-boot application that talks to MongoDB for GET/POST REST APIs and deployed in Kubernetes cluster.

Prerequisites

• minikube
• kubectl
• docker
• maven

Docker is a Linux container management toolkit with a “social” aspect, allowing users to publish container images and consume those published by others. A Docker image is a recipe for running a containerized process, and in this guide, we will build one for a simple Spring boot application.

Find the Github repository here.

Docker File:

FROM openjdk:8-jdk-alpine
ADD target/spring-boot-mongo-docker-1.0.0.jar app.jar
ENV JAVA_OPTS=””
ENTRYPOINT exec java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar /app.jar

Docker Compose:

version: “2.1”
services:
mongo:
image: mongo:3.2.4
ports:
– 27017:27017
command: –smallfiles

mongo-init:
build: ./mongo-init
links:
– mongo

mongo-client:
image: mongoclient/mongoclient
ports:
– 3030:3000
environment:
– MONGOCLIENT_DEFAULT_CONNECTION_URL=mongodb://mongo:27017
links:
– mongo

# APP ***************************************************************************************
spring-boot-mongo-docker:
image: aritranag20/spring-boot-mongo-docker
ports:
– 8080:8080
links:
– mongo
entrypoint: “java -Djava.security.egd=file:/dev/./urandom -jar /app.jar”

Set Up a Spring Boot App

If you want to run with Maven, execute:

./mvn package && java -jar target/spring-boot-mongo-docker-1.0.0.jar

and go to http://localhost:8080/customer/ to see your persisted customers.

Dockerisation

We need a container with JDK to run our Spring Boot application. There are many images with JDK 8 publicly available already, but just to get the end-to-end experience, we will built a minimal container based on Alpine Linux with JDK 8:

docker build -t  aritranag20/spring-boot-mongo-docker .

Then log into Docker, with your credentials after signing up on docker.io,

docker login

Execute the following command to push the image to the Docker registry.

docker push aritranag20/spring-boot-mongo-docker

Containerize It

If you want to run with Docker, execute:

./docker-compose up

Deploying on Kubernetes

Now that we have the image of our application available in the Docker registry, we can deploy it in a Kubernetes cluster. We will also set up a node for MongoDB to be used as a backend by our application.

Start local Kubernetes cluster with the following command:

minikube start

We can then launch a dashboard for the cluster:

minikube dashboard

Next, create the deployment of our application in the cluster.

kubectl create -f deployment.yml

We can see a description of the service with:

kubectl describe service spring-boot-mongo-docker

Now get the exact address of the service with:

minikube service spring-boot-mongo-docker

which will launch browser and point to the endpoint. For e.g. in my case,

curl http://192.168.99.101:30864/user =>
[{"id":"58bcd7ad5908010005cce257","firstName":"Arun","lastName":null,"email":null,"address":{"street1":null,"street2":null,"town":null,"postcode":null,"state":null}}]

Summary

Congratulations! You’ve just created a Docker container for a Spring Boot app with MongoDB and hosted the app in Kubernetes! Spring Boot apps run on port 8080 inside the container by default and we mapped that to the same port on the pods which is load balanced across multiple replicas of the service and can be assessed by getting the NodePort from  kubectl describe service spring-boot-mongo-docker  command.

Optional

Finally to stop your local kubernetes cluster:

minikube stop