📬 Notification Service (Microservice Architecture)

This repository demonstrates a microservices-based Notification System using Node.js with NestJS, RabbitMQ (message broker), and unit testing for building production-grade, scalable infrastructure. It is designed to process and deliver notifications (e.g., email, SMS) via queue-based architecture and strategy pattern.

✅ Ideal for developers and learners exploring real-world microservice design in Node.js.

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🛠 Tech Stack

Layer/Component	Technology Used
Framework	NestJS
Language	TypeScript
Messaging	RabbitMQ (via amqplib)
Email Client	SMTP / Nodemailer
Design Pattern	Strategy Pattern
Persistence	MongoDB (via Mongoose)
Validation	Joi, class-validator
Testing	Jest + Supertest
Containerization	Docker + Docker Compose

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📦 Project Structure

micro-notify/
├── services/
│   ├── notification-service/        # Main API service
│   │   ├── application/
│   │   ├── domain/
│   │   ├── infrastructure/
│   │   ├── presentation/
│   │   └── queue/                   # Queue publishing logic
│   └── email-worker/                # Worker service that consumes queue and sends emails
│       ├── queue/
│       └── mail/

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✅ Features

• REST API for triggering notifications
• RabbitMQ integration for decoupled message handling
• Email strategy using SMTP
• SMS strategy (stubbed for extension)
• Strategy Pattern for dynamic message handling (Email, SMS, etc.)
• Worker service that consumes queue and sends notifications
• Unit tests for controller layer (using Jest)
• Docker support for simplified local setup

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🚀 Getting Started

Prerequisites

• Node.js >= 18
• MongoDB running locally (mongodb://localhost:27017)
• RabbitMQ running locally (amqp://localhost)
• Docker (optional for running RabbitMQ/MongoDB containers)

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1️⃣ Clone the Repository

git clone https://github.com/yourusername/micro-notify.git
cd micro-notify

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2️⃣ Start RabbitMQ & MongoDB (Docker optional)

If you don’t have RabbitMQ locally, you can use:

docker-compose -f docker-compose.local.yml up -d

This will start RabbitMQ at localhost:5672 and MongoDB at localhost:27017.

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3️⃣ Install Dependencies

cd services/notification-service
npm install

cd ../email-worker
npm install

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4️⃣ Run Services

• Run Notification API:

cd services/notification-service
npm run start:dev

• Run Email Worker:

cd services/email-worker
npm run start:dev

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5️⃣ Trigger Notification

Send a POST request to:

POST http://localhost:3000/notifications

With body:

{
  "recipient": "test@example.com",
  "subject": "Welcome to our system",
  "body": "<b>Hello!</b> You have a new message.",
  "notificationType": "WELCOME",
  "mediaType": "EMAIL"
}

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🧪 Testing

cd services/notification-service
npm run test

✅ Jest-based unit tests are implemented for controller endpoints.

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📦 Dockerization

Each service has its own Dockerfile.

You can also run both services together using a full docker-compose.yml (optional).

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🧠 Learning Outcomes

This project helps you learn:

• Microservice architecture using NestJS
• Queue-based communication using RabbitMQ
• Dynamic messaging using the Strategy pattern
• Dependency injection and modular codebase
• Controller, Service, and Factory design separation
• Robust error handling and reconnection logic
• Writing unit tests for REST APIs

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📚 Future Enhancements

• Add support for AWS SNS/SQS
• Extend SMS sending via Twilio
• Add custom retry logic for failed messages
• UI dashboard for queue monitoring
• Log aggregator (e.g., ELK or Prometheus)

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📧 Contact

Author: Mostafizur Rahman LinkedIn: linkedin.com/in/mostafiz Email: mostafiz571@gmail.com

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📜 License

This project is open-source and available under the MIT License.

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Full Project Structure

micro-notify/
├── services/                       # Microservices directory
│   ├── notification-service/      # Core notification logic
│   ├── user-service/              # Authentication and user management
│   ├── email-worker/              # Email processing worker
│   ├── audit-service/             # Logging and auditing
│   └── api-gateway/               # API Gateway
├── ui/                            # Next.js frontend dashboard
├── docker-compose.yml             # Container orchestration
├── .env.example                   # Environment variables template
└── README.md                      # Project documentation

Services Overview

• notification-service: Handles core notification logic and storage
• user-service: Manages authentication and user profiles
• email-worker: Processes email notifications asynchronously
• audit-service: Handles logging and auditing of operations
• api-gateway: Central entry point for all API requests
• ui: Next.js based frontend dashboard

Getting Started

1. Clone the repository
2. Copy .env.example to .env and configure environment variables
3. Run docker-compose up to start all services