Kubernetes for Impatient Java Developers

Project presentation for JConf Peru 2025

This is a basic Quarkus Maven project configured to explore Kubernetes concepts with easy deployment to local clusters (like k3s) and external clusters (like Red Hat OpenShift Sandbox).

🚀 Features

• ✅ RESTful API with two endpoints
• ✅ Health checks (liveness, readiness, startup)
• ✅ Automatic Kubernetes manifest generation
• ✅ Container image build with JIB
• ✅ Ready for k3s and OpenShift deployment
• ✅ JSON support with Jackson

📋 Prerequisites

• Java 17+
• Maven 3.9+
• Docker (for container image builds)
• kubectl (for Kubernetes deployments)
• k3s, minikube, or access to Red Hat OpenShift Sandbox

🏃 Running the Application Locally

Development Mode

Run the application in dev mode with live coding enabled:

./mvnw quarkus:dev

The application will be available at:

• Main app: http://localhost:8080
• Dev UI: http://localhost:8080/q/dev/
• Health: http://localhost:8080/health

Test the Endpoints

# Simple greeting
curl http://localhost:8080/hello

# Application info
curl http://localhost:8080/hello/info

# Health check
curl http://localhost:8080/health

�� Building Container Images

Build with JIB (no Docker daemon required)

./mvnw clean package -Dquarkus.container-image.build=true

This creates a container image: jconfperu/quarkus-k8s-demo:1.0.0-SNAPSHOT

Push to Registry (optional)

./mvnw clean package \
  -Dquarkus.container-image.build=true \
  -Dquarkus.container-image.push=true \
  -Dquarkus.container-image.registry=docker.io \
  -Dquarkus.container-image.username=<your-username> \
  -Dquarkus.container-image.password=<your-password>

☸️ Deploying to Kubernetes

Generate Kubernetes Manifests

Kubernetes manifests are automatically generated during the build in target/kubernetes/:

./mvnw clean package

The generated files include:

• target/kubernetes/kubernetes.yml - Complete Kubernetes deployment
• target/kubernetes/kubernetes.json - JSON format

Deploy to Local k3s Cluster

1. Install k3s (if not already installed):

curl -sfL https://get.k3s.io | sh -

2. Build and load the image:

# Build the container image
./mvnw clean package -Dquarkus.container-image.build=true

# Import to k3s (if using local registry)
docker save jconfperu/quarkus-k8s-demo:1.0.0-SNAPSHOT | sudo k3s ctr images import -

3. Deploy to k3s:

sudo kubectl apply -f target/kubernetes/kubernetes.yml

4. Check deployment status:

sudo kubectl get pods
sudo kubectl get svc quarkus-k8s-demo

5. Access the application:

# Get the service URL
sudo kubectl get svc quarkus-k8s-demo

# Port forward to access locally
sudo kubectl port-forward svc/quarkus-k8s-demo 8080:80

6. Test the application:

curl http://localhost:8080/hello
curl http://localhost:8080/hello/info

Deploy to Red Hat OpenShift Sandbox

1. Login to OpenShift:

oc login --token=<your-token> --server=<your-server>

2. Build and deploy with OpenShift profile:

./mvnw clean package -Dquarkus.profile=openshift \
  -Dquarkus.container-image.build=true \
  -Dquarkus.kubernetes.deploy=true

This will:

• Build the container image
• Push to OpenShift's internal registry
• Deploy the application
• Create a Route for external access

3. Get the application URL:

oc get route quarkus-k8s-demo

4. Access the application:

curl https://<route-url>/hello
curl https://<route-url>/hello/info

🧪 Running Tests

./mvnw test

📦 Packaging Options

Standard JAR

./mvnw package
java -jar target/quarkus-app/quarkus-run.jar

Uber JAR

./mvnw package -Dquarkus.package.jar.type=uber-jar
java -jar target/quarkus-k8s-demo-1.0.0-SNAPSHOT-runner.jar

Native Executable

./mvnw package -Dnative -Dquarkus.native.container-build=true
./target/quarkus-k8s-demo-1.0.0-SNAPSHOT-runner

🔧 Configuration

Key configuration properties in src/main/resources/application.properties:

• quarkus.kubernetes.replicas=2 - Number of replicas
• quarkus.kubernetes.service-type=LoadBalancer - Service type
• quarkus.container-image.group=jconfperu - Container image group
• quarkus.container-image.build=false - Auto-build images

📚 API Endpoints

Endpoint	Method	Description
/hello	GET	Returns a greeting message
/hello/info	GET	Returns application information (JSON)
/health	GET	SmallRye health check endpoint
/health/live	GET	Liveness probe
/health/ready	GET	Readiness probe
/health/started	GET	Startup probe

🛠️ Technology Stack

• Quarkus 3.17.5 - Supersonic Subatomic Java Framework
• Java 17 - LTS version
• RESTEasy Reactive - JAX-RS implementation
• Jackson - JSON processing
• SmallRye Health - Health check implementation
• Quarkus Kubernetes - Automatic manifest generation
• JIB - Container image building without Docker

📖 Learn More

• Quarkus
• Quarkus Kubernetes Guide
• Quarkus Container Images Guide
• k3s Documentation
• Red Hat OpenShift Sandbox

🤝 Contributing

This is a demo project for JConf Peru 2025. Feel free to fork and experiment!

📝 License

This project is open source and available under standard terms.