Load-Balanced URL Shortener

A scalable URL shortening service built with Flask and MySQL, deployed on Kubernetes with load balancing capabilities.

Features

• URL shortening and redirection
• Load balancing across multiple replicas
• Persistent MySQL storage
• Horizontal Pod Autoscaling (HPA)
• Stress testing capabilities
• Monitoring and metrics

Prerequisites

1. Install the following tools:

   • Docker Desktop with WSL2 backend
   • Minikube
   • kubectl
   • Python 3.x (for local development)

2. Verify installations

docker --version
minikube version
kubectl version

Linux/WSL Installation

# Install Docker
sudo apt-get update
sudo apt-get install docker.io

# Install Minikube
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64
sudo install minikube-linux-amd64 /usr/local/bin/minikube

# Install kubectl
curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl

Project Setup

1. Clone the repository:

git clone https://github.com/shrxyyya/Load-balanced-URL-Shortener.git
cd Load-balanced-URL-Shortener

2. Start Minikube:

# Start Minikube with Docker driver
minikube start --driver=docker

# Verify Minikube is running
minikube status

3. Build and deploy the application:

# Point shell to minikube's docker-daemon
eval $(minikube docker-env)

# Build the Docker image
docker build -t urlshortener:latest .

# Apply Kubernetes configurations
kubectl apply -f k8s/mysql-secret.yaml
kubectl apply -f k8s/mysql-pvc.yaml
kubectl apply -f k8s/mysql-configmap.yaml
kubectl apply -f k8s/urlshortener-config.yaml
kubectl apply -f k8s/mysql-deployment.yaml
kubectl apply -f k8s/urlshortener-deployment.yaml

# Verify all pods are running
kubectl get pods -w

4. Access the application:

# Terminal 1: Start minikube tunnel (keep this terminal open)
minikube tunnel

# Terminal 2: Forward MySQL port (keep this terminal open) - because my server was created on port 3307
kubectl port-forward service/mysql-service 3307:3306

# Terminal 3: Get the service URL
kubectl get service urlshortener-service

The application will be available at http:// shown in the service output.

Testing

Basic API Testing

1. Make the test script executable:

chmod +x test_api.sh
dos2unix test_api.sh

2. Run the test script:

./test_api.sh

This will:

• Create 10 shortened URLs
• Test redirections
• Show load balancing across pods

Stress Testing

1. Basic Stress Test:

# Terminal 4: Monitor CPU usage
watch -n 2 "kubectl top pods | grep urlshortener"

# -- OR --
# Terminal 4: Monitor HPA - Check current replica set information
kubectl get hpa urlshortener-hpa

# Terminal 3: Run basic stress test
./basic_stress_test.sh

2. Advanced Stress Test:

# Terminal 3: Run advanced stress test
./adv_stress_test.sh

The stress tests will:

• Simulate multiple concurrent users
• Test system performance under load
• Monitor response times and success rates
• Verify load balancing effectiveness

Monitoring

1. View application logs:

# View URL shortener logs
kubectl logs -l app=urlshortener

# View MySQL logs
kubectl logs -l app=mysql

Troubleshooting

1. If pods are not starting:

kubectl describe pods

2. If the service is not accessible:

# Check service status
kubectl get services

# Check service endpoints
kubectl get endpoints urlshortener-service

3. To restart deployments:

kubectl rollout restart deployment urlshortener-deployment
kubectl rollout restart deployment mysql-deployment

Cleanup

To stop and clean up the project:

# Delete all resources
kubectl delete -f k8s/

# Stop minikube
minikube stop

# Optional: Delete minikube cluster
minikube delete

Environment Variables

The application uses the following environment variables (configured in ConfigMaps and Secrets):

• MYSQL_HOST: MySQL service hostname
• MYSQL_PORT: MySQL port (default: 3306)
• MYSQL_USER: MySQL username
• MYSQL_PASSWORD: MySQL password (in secret)
• MYSQL_DATABASE: Database name
• FLASK_ENV: Flask environment

Architecture

The application consists of:

• MySQL Deployment (single pod for data consistency)
• URL Shortener Deployment (3 replicas for high availability)
• Persistent Volume for MySQL data
• Load Balancer Service for external access
• Horizontal Pod Autoscaler for dynamic scaling