Web Application Containerization Exercise

This exercise will help you explore containerization, Docker, and Kubernetes basics. You'll containerize a simple web application that displays an environment variable.

Prerequisites

• Docker installed
• Minikube installed
• kubectl installed
• Docker Hub account

Files Provided

• index.html: Basic web page
• server.js: Simple Node.js server

Exercise Steps

1. Create Dockerfile

Create a Dockerfile that:

• Uses node:alpine as base image
• Sets up a working directory
• Copies both HTML and JS files
• Exposes port 3000
• Runs the Node.js server

2. Build and Test Docker Image Locally

# Build image (replace USERNAME with your Docker Hub username and provide a version number of your choice)
docker build -t USERNAME/capstone-web:<version> .

# Test locally
docker run -d -p 8080:3000 -e APPNAME="Local Test App" USERNAME/capstone-web:latest

# Verify in browser
open http://localhost:8080

3. Push to Docker Hub

# Login to Docker Hub
docker login

# Push image
docker push USERNAME/capstone-web:latest

4. Create Kubernetes Deployment YAML

Create a deployment.yaml that includes:

• Deployment resource
  • 2 replicas
  • Container image from your Docker Hub
  • Environment variable APPNAME
  • Container port 3000
• NodePort service
  • Maps to port 3000
  • NodePort type

5. Deploy to Minikube

# Start Minikube if not running
minikube start

# Apply deployment
kubectl apply -f deployment.yaml

# Get NodePort
kubectl get svc

# Get Minikube IP
minikube ip

6. Test Deployment

Access your application at:

http://MINIKUBE_IP:NODEPORT

Success Criteria

• Docker image builds successfully
• Application runs locally with Docker
• Application shows environment variable value
• Kubernetes deployment works
• Application accessible via NodePort
• Environment variable displays correctly in K8s deployment

Troubleshooting Tips

• Use docker ps to check running containers
• Use docker logs CONTAINER_ID for container logs
• Use kubectl get pods to check pod status
• Use kubectl describe pod POD_NAME for detailed pod info
• Use kubectl logs POD_NAME for pod logs

Clean Up

# Stop local Docker container
docker ps
docker stop CONTAINER_ID

# Delete K8s deployment
kubectl delete -f deployment.yaml

# Stop Minikube (optional)
minikube stop