The Resilient Notification Gateway

This project is a Node.js microservice designed to send notifications reliably using multiple providers with failover support.

• Provider failover (Primary → Secondary)
• Idempotency using Redis (Duplicate requests are blocked)
• Rate limiting using Redis (10 requests/minute per user)
• Structured logging using Winston
• Health-check endpoint for service and Redis monitoring

• Node.js + Express
• Redis
• BullMQ
• Winston
• TypeScript

Client → API → Middleware → Controller → Service (enqueue jobs) → Queue (BullMQ backed by Redis) → Worker (process jobs) → Primary Provider → Secondary Provider (failover)

npm install

docker run -d -p 6379:6379 redis

npm run start:all

{
  "userId": "1",  
  "message": "Hello",
  "type": "email"
}

• 202 Accepted – Notification queued successfully

• Provider Handling

{"jobId":"1","level":"info","message":"Sent via secondary provider","service":"notification-service"}

• Idempotency

{"key":"notification:2:Hello","level":"warn","message":"Duplicate request blocked","service":"notification-service","userId":"2"}

• Rate Limiting

{"level":"warn","message":"Rate limit exceeded","service":"notification-service","userId":"2"}

• Health Check

{"level":"info","message":"Health check called","service":"notification-service","uptime":24.1770609}

curl -X POST http://localhost:3000/notifications \
-H "Content-Type: application/json" \
-d '{"userId":"1","message":"Hello","type":"email"}'

Endpoint: POST http://localhost:3000/notifications

Headers: Content-Type: application/json

Body (JSON): To check Idempotency

{
  "userId": "1",
  "message": "Hello",
  "type": "email"
}

Body (JSON): To check Rate Limiting

{
  "userId": "1",
  "message": "msg{{$randomInt}}",
  "type": "email"
}

Health-check Endpoint: GET http://localhost:3000/health

• This endpoint verifies that the service is running and that the Redis connection is healthy

Response:

{
  "status": "ok",
  "uptime": 123.45,
  "timestamp": "2026-03-20T10:00:00.000Z"
}

• To check Provider Failover

npm test