Target

Target of this repository is show how to build spring boot application Docker image and deploy it with kind and k8s at least in local.

Prerequisites

We will need next tools installed:

1. JDK 8+
2. Docker
3. Kubernetes
4. Kind

Project

This is simple rest application that response with 'Hello World!' on root rout. To get try you can clone it with:

git clone https://github.com/demkom58/gradle-spring-boot-deploy-example.git

or

git clone [email protected]:demkom58/gradle-spring-boot-deploy-example.git

Build

We can build Docker image using Cloud Native Buildpacks (Paketo Buildpacks) without writing any Dockerfile or Docker-compose.

To build image we need spring boot plugin. Here are few examples:

Maven

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>

Gradle

plugins {
    id 'org.springframework.boot' version '2.5.4'
}

It's included by default in spring start project generator. Now we can start Docker and enter command to build image:

Gradle	Maven
./gradlew bootBuildImage	./mvnw spring-boot:build-image

When execution will be done, we should see new image appeared in docker images with name of project and current version of project in tag.

Open terminal and enter docker images gradle-spring-boot-deploy-example:0.0.1-SNAPSHOT to get detailed info about built image. Result:

REPOSITORY                          TAG              IMAGE ID       CREATED        SIZE
gradle-spring-boot-deploy-example   0.0.1-SNAPSHOT   93abbee19f85   41 years ago   289MB

To check that everything build right we can run our image and check out application. Also, just for fun we can redirect port 8080 to 80: docker run --name gradle-spring-boot-deploy-example -p 80:8080 gradle-spring-boot-deploy-example:0.0.1-SNAPSHOT

Go to localhost or localhost:80 in your web browser and check that everything works correctly, we should get in response:

Hello World!

We can stop container using Ctrl + C and remove container using docker rm gradle-spring-boot-deploy-example.

Deploy

Let's start Kubernetes cluster using kind:

kind create cluster

We need say K8s to load Docker image from registry like that:

kind load docker-image gradle-spring-boot-deploy-example:0.0.1-SNAPSHOT

To create deployment in k8s open terminal and enter next command:

kubectl create deployment example-app --image=gradle-spring-boot-deploy-example:0.0.1-SNAPSHOT

Now we can use kubectl get deployment to get deployments and kubectl get pod to get pods.

> kubectl get deployment
NAME          READY   UP-TO-DATE   AVAILABLE   AGE
example-app   1/1     1            1           44s

> kubectl get pod
NAME                           READY   STATUS    RESTARTS   AGE
example-app-584b66b696-q6ggs   1/1     Running   0          46s

Now we need make application in k8s accessible from outside. Using next command we will expose our deployment's port 8080:

kubectl expose deployment example-app --type=ClusterIP --name=gradle-spring-boot-deploy-example --port=8080

We can check created services with kubectl get svc:

> kubectl get svc
NAME                                TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)   AGE
gradle-spring-boot-deploy-example   ClusterIP   10.96.58.78   <none>        8080/TCP    34s
kubernetes                          ClusterIP   10.96.0.1     <none>        443/TCP   25m

Now let's configure port forwarding like with Docker, execute: kubectl port-forward service/gradle-spring-boot-deploy-example 801:8080

Open localhost:801 in web browser, and we should see same response that have with docker only :)

To terminate port forwarding we can press Ctrl + C

Clear workspace

1. To delete service enter: kubectl delete svc gradle-spring-boot-deploy-example
2. To delete deployment enter: kubectl delete deployment example-app
3. To delete cluster enter: kind delete cluster