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SSE Implementation Summary

What Was Implemented

✅ Server-Sent Events (SSE) for real-time stream updates
✅ Subscription filtering (by stream ID, user, or all events)
✅ Automatic client management and cleanup
✅ Broadcasting system with targeted delivery
✅ Connection statistics endpoint
✅ Complete documentation with examples
✅ HTML test client

Architecture Decision: SSE vs WebSockets

Chose SSE because:

  • Unidirectional (server → client) fits DeFi streaming use case
  • Simpler implementation, automatic reconnection
  • Lower overhead for broadcasting updates
  • Better HTTP/2 compatibility
  • Easier to debug and monitor

Files Created

backend/
├── src/
│   ├── services/
│   │   └── sse.service.ts          # Core SSE service
│   ├── controllers/
│   │   └── sse.controller.ts       # SSE endpoint handler
│   └── routes/
│       └── events.routes.ts        # /events routes
├── docs/
│   └── SSE_IMPLEMENTATION.md       # Full documentation
└── test-sse-client.html            # Test client

Files Modified

  • src/app.ts - Added events routes
  • src/controllers/stream.controller.ts - Integrated SSE broadcasting

API Endpoints

Subscribe to Events

GET /events/subscribe?streams=1&streams=2
GET /events/subscribe?users=GABC...
GET /events/subscribe?all=true

Connection Stats

GET /events/stats

Event Types

  • stream.created - New stream created
  • stream.topped_up - Stream received funds
  • stream.withdrawn - Funds withdrawn
  • stream.cancelled - Stream cancelled
  • stream.completed - Stream completed

Quick Test

  1. Start the backend:
cd backend
npm run dev
  1. Open test client:
open test-sse-client.html
# or
python3 -m http.server 8000
# then visit http://localhost:8000/test-sse-client.html
  1. Test with curl:
curl -N http://localhost:3001/events/subscribe?all=true
  1. Trigger an event:
curl -X POST http://localhost:3001/streams \
  -H "Content-Type: application/json" \
  -d '{
    "sender": "GABC...",
    "recipient": "GDEF...",
    "tokenAddress": "CUSDC...",
    "ratePerSecond": "1000000",
    "depositedAmount": "86400000000",
    "startTime": 1708560000
  }'

Production Considerations

Security

  • Add JWT authentication to /events/subscribe
  • Implement per-IP connection limits
  • Use reverse proxy (nginx/CloudFlare) for DDoS protection

Scaling

  • Add Redis pub/sub for multi-instance deployments
  • Monitor connection count and set alerts
  • Implement connection pooling limits

Monitoring

  • Track active connections
  • Monitor events/second
  • Alert on reconnection spikes

Load Testing

Expected capacity (single instance):

  • 10,000 connections: ~100MB memory
  • 1,000 events/sec: Minimal CPU impact
  • Connection overhead: ~10KB per client

Next Steps

  1. Integrate with actual blockchain indexer
  2. Add authentication middleware
  3. Implement Redis for horizontal scaling
  4. Add Prometheus metrics
  5. Create frontend React hook
  6. Add E2E tests

Documentation

Full documentation: backend/docs/SSE_IMPLEMENTATION.md

Includes:

  • Client implementation examples (JS, React)
  • Reconnection strategies
  • Load & security considerations
  • Horizontal scaling guide
  • Monitoring recommendations