🔔 Notification Service

Notification Service is an asynchronous microservice built with FastAPI for managing and delivering notifications across multiple channels (Email, Telegram, In-App). Designed with scalability and high performance in mind, it leverages background task processing and real-time WebSocket communication.

🚀 Key Features

• Multi-Channel Delivery: Seamlessly send messages via Email (SMTP), Telegram (Bot API), and In-App (WebSockets).
• Asynchronous Architecture: Fully async implementation using FastAPI, asyncpg, and SQLAlchemy 2.0 for maximum throughput.
• Background Processing: Time-consuming tasks (like reaching out to 3rd-party APIs or SMTP servers) are offloaded to Celery workers using Redis as a message broker.
• Real-Time Updates: Clients instantly receive notification statuses via WebSockets powered by Redis Pub/Sub for cross-worker event broadcasting.
• Secure Authentication: JWT-based authentication (access tokens) and secure password hashing (bcrypt).
• Templating Engine: Create and manage dynamic notification templates using Jinja-like variables ({{ username }}, {{ user_id }}).
• Containerized: Ready for deployment with Docker and Docker Compose, wrapping the API, Celery worker, PostgreSQL, and Redis in a single isolated environment.

🛠️ Tech Stack

• Backend Framework: FastAPI, Pydantic
• Database & ORM: PostgreSQL, SQLAlchemy 2.0 (async), Alembic (Migrations)
• Task Queue & Cache: Celery, Redis
• Real-time: WebSockets, Redis Pub/Sub
• Testing: Pytest, pytest-asyncio, HTTPX
• Deployment: Docker, Docker Compose

🏗️ Architecture

graph TB
    Client["Client (HTTP)"] -->|POST /notifications/send| API["FastAPI"]
    WS_Client["Client (WS)"] <-->|WebSocket| API

    API -->|"Save to DB (status=pending)"| DB[(PostgreSQL)]
    API -->|"Publish Task"| Broker["Redis (Broker)"]
    Broker --> Worker["Celery Worker"]

    Worker -->|Email| SMTP["SMTP Server"]
    Worker -->|Telegram| TG["Telegram Bot API"]
    Worker -->|In-App| RedisPub["Redis Pub/Sub"]

    RedisPub -->|"Push Event"| API
    API -->|"WebSocket Push"| WS_Client

    Worker -->|"Update Status"| DB

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⚙️ Quick Start (Docker)

1. Clone the repository

   git clone https://github.com/your-username/notification-service.git
   cd notification-service

2. Set up Environment Variables Create a .env file based on the template (provide your DB credentials, SMTP, and Telegram tokens).

3. Run with Docker Compose

   docker-compose up --build -d

   The API will be available at http://localhost:8000.

4. Apply Database Migrations (if not run automatically)

   docker exec -it notify-api alembic upgrade head

📚 API Endpoints Overview

Interactive documentation available at http://localhost:8000/docs (Swagger UI).

• Auth: POST /auth/register, POST /auth/login
• Templates: GET /templates/, POST /templates/, GET /templates/{id}, PATCH /templates/{id}, DELETE /templates/{id}
• Notifications:
  • POST /notifications/send - Schedule a notification (background task)
  • GET /notifications/ - History & Pagination
  • GET /notifications/stats - Delivery statistics
  • GET /notifications/{id} - Specific notification status
• WebSocket: ws://localhost:8000/ws/notifications- Connect to receive live updates.

🧪 Testing

The project includes a comprehensive test suite using pytest and an in-memory SQLite database to mock services and test business logic without external dependencies.

pytest tests/ -v