Event-Driven Microservices with NestJS

A modern microservices architecture implementation using NestJS, Kafka, and Event Sourcing patterns. This project demonstrates how to build scalable and maintainable microservices using CQRS and Event Sourcing principles.

Project Structure

EVENT-DRIVEN-NESTJS/
├── api-gateway/               # API Gateway service
├── inventory-service/         # Inventory management service
├── order-service/            # Order management service
│   ├── src/
│   │   ├── api/
│   │   │   └── controllers/  # API Controllers
│   │   ├── application/
│   │   │   ├── handlers/     # Command and Event Handlers
│   │   │   └── sagas/       # Sagas for process management
│   │   ├── domain/
│   │   │   ├── aggregates/  # Domain Aggregates
│   │   │   ├── commands/    # Command Definitions
│   │   │   ├── events/      # Event Definitions
│   │   │   └── interfaces/  # Domain Interfaces
│   │   └── infrastructure/
│   │       ├── persistence/ # Database and Event Store
│   │       └── messaging/   # Kafka Integration
├── payment-service/          # Payment processing service
├── shared-lib/              # Shared code and utilities
│   ├── src/
│   │   ├── commands/        # Shared Commands
│   │   ├── events/          # Shared Events
│   │   ├── interfaces/      # Shared Interfaces
│   │   └── utils/          # Utility Functions
└── docker-compose.yml       # Docker composition for services

Features

• ✨ Event-Driven Architecture
• 🎯 CQRS Pattern Implementation
• 📊 Event Sourcing
• 🚀 Microservices Architecture
• 🔄 Apache Kafka Integration
• 🛡️ TypeScript Support
• 🐳 Docker Support

Current Implementation

Order Service

• Create Order API with Event Sourcing
• Command and Event Handlers
• Database persistence with TypeORM
• Event Store implementation
• Kafka integration for event publishing

Prerequisites

• Node.js (v18 or higher)
• Docker and Docker Compose
• MySQL
• Apache Kafka

Getting Started

1. Clone the repository:

git clone [your-repository-url]
cd event-driven-nestjs

2. Install dependencies:

# Install shared library dependencies
cd shared-lib
npm install

# Install service dependencies
cd ../order-service
npm install

3. Start the infrastructure services:

docker-compose up -d

4. Run the services:

# Start order service
cd order-service
npm run start:dev

API Endpoints

Order Service

• POST /api/orders - Create a new order

  {
    "userId": "string",
    "items": [
      {
        "id": "string",
        "quantity": number,
        "price": number
      }
    ]
  }

Architecture

This project follows these architectural patterns:

• Event Sourcing: All changes to the domain objects are stored as a sequence of events
• CQRS: Separation of command and query responsibilities
• Microservices: Distributed system with separate services for different business capabilities

Technical Stack

• Framework: NestJS
• Message Broker: Apache Kafka
• Database: MySQL
• ORM: TypeORM
• API Documentation: Swagger (coming soon)
• Container: Docker
• Language: TypeScript

Upcoming Features

• Inventory Service Implementation
• Payment Service Integration
• API Gateway Implementation
• Service Discovery
• Distributed Tracing
• API Documentation
• Unit and Integration Tests
• CI/CD Pipeline

Development

# Start development server
npm run start:dev

# Build the project
npm run build

# Run tests (coming soon)
npm run test

Docker Support

The project includes Docker support for easy development and deployment:

# Start all services
docker-compose up -d

# Stop all services
docker-compose down

# View logs
docker-compose logs -f

Running with Docker

The services are containerized using Docker. Use the following commands to run the entire system:

1. Start the services:

docker-compose up -d

2. Check service status:

docker-compose ps

3. View service logs:

docker-compose logs -f [service-name]

4. Stop the services:

docker-compose down

Environment Configuration

Each service requires specific environment variables. Create a .env file in each service directory:

Order Service

# Database
DB_HOST=mysql
DB_PORT=3306
DB_USER=user
DB_PASS=password
DB_NAME=eventstore

# Kafka
KAFKA_BROKER=kafka:9092
KAFKA_GROUP_ID=order-service-group

Contributing

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

License

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

Contact

Reza Masoomi Niaragh - [email protected]

Project Link: https://github.com/rezamasoomin/event-driven-nestJs