🏗️ Microservices & Distributed Systems

A comprehensive microservices architecture built with Spring Boot, featuring service discovery, message queuing, distributed tracing, and containerization.

🏛️ Architecture Overview

🚀 Services

Core Microservices

• 👤 Customer Service - Port 8080
• 🛡️ Fraud Detection Service - Port 8081
• 📧 Notification Service - Port 8082

Infrastructure Services

• 🎯 Eureka Server - Service Discovery (Port 8761)
• 🚪 API Gateway - Spring Cloud Gateway (Port 8080)
• ⚙️ Config Server - Centralized Configuration (Port 8888)

🛠️ Technology Stack

Component	Technology
Framework	Spring Boot 2.5.7
Language	Java 17
Database	PostgreSQL
Message Broker	RabbitMQ
Service Discovery	Netflix Eureka
API Gateway	Spring Cloud Gateway
Containerization	Docker
Distributed Tracing	Zipkin + Sleuth
Build Tool	Maven

🗄️ Database Configuration

Database Credentials:
  Username: devarifkhan
  Password: password
  Database: mds
  Port: 5433 (local) / 5432 (docker)

🚀 Quick Start

Prerequisites

• Java 17+
• Maven 3.6+
• Docker & Docker Compose
• PostgreSQL

1. Clone Repository

git clone <repository-url>
cd microservices_and_distributed_systems

2. Build All Services

mvn clean install

3. Start Infrastructure (Docker)

docker-compose up -d postgres rabbitmq zipkin

4. Start Services

# Start Eureka Server
cd eureka-server && mvn spring-boot:run

# Start Config Server  
cd config-server && mvn spring-boot:run

# Start API Gateway
cd apigw && mvn spring-boot:run

# Start Core Services
cd customer && mvn spring-boot:run
cd fraud && mvn spring-boot:run  
cd notification && mvn spring-boot:run

🐳 Docker Deployment

Build Images

mvn clean package -Pbuild-docker-image

Run with Docker Compose

docker-compose up

📡 Service Endpoints

Service	Local URL	Docker URL
Eureka Dashboard	http://localhost:8761	http://eureka-server:8761
API Gateway	http://localhost:8080	http://apigw:8080
Customer API	http://localhost:8080/customer	http://customer:8080
Fraud API	http://localhost:8080/fraud	http://fraud:8081
Zipkin UI	http://localhost:9411	http://zipkin:9411

🔧 Configuration Profiles

Each service supports multiple profiles:

• default - Local development
• docker - Docker container deployment
• kube - Kubernetes deployment

📨 Message Queue Architecture

RabbitMQ Configuration

Exchanges:
  - internal.exchange (Topic)

Queues:
  - notification.queue

Routing Keys:
  - internal.notification.routing-key

Message Flow

1. Customer Service → Publishes events → Exchange
2. Fraud Service → Publishes events → Exchange
3. Exchange → Routes messages → Notification Queue
4. Notification Service → Consumes messages → Sends notifications

🔍 Distributed Tracing

All services integrate with Zipkin via Spring Cloud Sleuth:

• Automatic trace generation
• Cross-service correlation
• Performance monitoring
• Request flow visualization

🛡️ Security Features

• API Key Authentication via API Gateway
• Rate Limiting and throttling
• SSL/TLS encryption
• JWT Token validation
• OAuth 2.0 authorization

📊 Monitoring & Observability

• Health Checks - Spring Boot Actuator
• Metrics Collection - Micrometer
• Distributed Tracing - Zipkin + Sleuth
• Centralized Logging - ELK Stack ready

🏗️ Project Structure

microservices_and_distributed_systems/
├── customer/           # Customer microservice
├── fraud/             # Fraud detection service  
├── notification/      # Notification service
├── eureka-server/     # Service discovery
├── apigw/            # API Gateway
├── clients/          # Shared client libraries
├── amqp/             # Message queue utilities
├── k8s/              # Kubernetes manifests
├── docker-compose.yml # Docker orchestration
└── pom.xml           # Parent POM

🔄 Communication Patterns

Synchronous Communication

• Customer → Fraud (HTTP REST)
• API Gateway → All Services (HTTP REST)

Asynchronous Communication

• Customer → RabbitMQ → Notification
• Fraud → RabbitMQ → Notification

🚀 API Examples

Create Customer

curl -X POST http://localhost:8080/api/v1/customers \
  -H "Content-Type: application/json" \
  -d '{
    "firstName": "John",
    "lastName": "Doe", 
    "email": "[email protected]"
  }'

Check Fraud

curl -X GET http://localhost:8080/api/v1/fraud-check/1

🐛 Troubleshooting

Common Issues

1. Port Conflicts

   # Check port usage
   netstat -tulpn | grep :8080

2. Database Connection

   # Test PostgreSQL connection
   psql -h localhost -p 5433 -U devarifkhan -d mds

3. Service Discovery

   • Check Eureka Dashboard: http://localhost:8761
   • Verify service registration

📈 Performance Tuning

JVM Options

-Xms512m -Xmx1024m
-XX:+UseG1GC
-XX:MaxGCPauseMillis=200

Database Optimization

spring:
  datasource:
    hikari:
      maximum-pool-size: 20
      minimum-idle: 5

🤝 Contributing

1. Fork the repository
2. Create feature branch (git checkout -b feature/amazing-feature)
3. Commit changes (git commit -m 'Add amazing feature')
4. Push to branch (git push origin feature/amazing-feature)
5. Open Pull Request

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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