Distributed Notification System

Overview

This is a scalable, microservices-based system for multi-channel notifications (email & push).
The solution is composed of the following services:

• api-gateway (Laravel): Main entrypoint & orchestrator.
• user-service (NestJS): Manages user profiles, contact info, notification preferences.
• template-service (NestJS): Manages notification templates, variable rendering.
• email-service (NestJS): Delivers email notifications.
• push-service (NestJS): Delivers push notifications.
• rabbitmq: Queue broker powering async delivery and retries.
• postgres: Data storage for gateway/service state.
• redis: Caching and idempotency for notifications.
• nginx: Reverse proxy and static asset handler.

Architecture

See system-design.png for full diagram.

Main Flow:

1. Client/system sends notification request to API Gateway.
2. Gateway validates data, checks idempotency, fetches user info.
3. Notification details are stored in DB and published to RabbitMQ.
4. Email and Push services consume queue messages, fetch templates, personalize, deliver notifications.
5. Services post delivery status updates to API Gateway, which updates notification records.
6. Monitoring endpoints and logs provide visibility into system health and operations.

Features

• Idempotency and duplicate prevention.
• Horizontal scaling of API and delivery services.
• Dead letter queues and retry strategies for failed messages.
• Real-time queue monitoring via RabbitMQ UI (localhost:15672).
• Centralized health checks for all dependencies.

Getting Started

Prerequisites

• Docker (and docker-compose)
• NodeJS / npm
• PHP >= 8.2
• Composer

Setup

1. Clone repository

   git clone <repo-url>
   cd distributed-notification-system
   

2. Start all services

   docker-compose up --build
   

3. Access API Gateway

   • Via Nginx:
     http://localhost:8000

4. RabbitMQ management

   • http://localhost:15672 (guest/guest)

5. Run tests

   • API Gateway:

     cd api-gateway
     php artisan test
     

Service Endpoints

Service	Port	Description
api-gateway	8000	Main API
user-service	4000	User profiles & preferences
template-service	4100	Template management
email-service	4200	Email delivery
push-service	4300	Push delivery
rabbitmq	5672/15672	Queue broker / Management UI
postgres	5432	Database
redis	6379	Cache

Folder Structure

distributed-notification-system/ ├── api-gateway/ ├── user-service/ ├── email-service/ ├── push-service/ ├── template-service/ ├── nginx.conf ├── docker-compose.yml └── system-design.png

Configuration

• All environment variables for each service are managed in their respective .env files.
• Make sure to adjust connection strings, secrets, and ports as needed per environment.

Scaling & Deployment

• The system supports horizontal scaling for stateless services.
• Queued message ingestion auto-scales with consumers.
• Can be deployed to any cloud or on-premise environment supporting Docker.

Troubleshooting

• Check logs (docker-compose logs <service>).
• Use health endpoints (/v1/health, etc.).
• Access RabbitMQ management for message queue diagnostics.

License

MIT

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