docs/components/WEBSOCKET_API_IMPLEMENTATION.md

# WebSocket & API Implementation Summary

## Overview
Production-ready WebSocket support and comprehensive REST API have been successfully implemented for the Crypto API Monitoring System.

## Files Created/Updated

### 1. `/home/user/crypto-dt-source/api/websocket.py` (NEW)
Comprehensive WebSocket implementation with:

#### Features:
- **WebSocket Endpoint**: `/ws/live` - Real-time monitoring updates
- **Connection Manager**: Handles multiple concurrent WebSocket connections
- **Message Types**:
  - `connection_established` - Sent when client connects
  - `status_update` - Periodic system status (every 10 seconds)
  - `new_log_entry` - Real-time log notifications
  - `rate_limit_alert` - Rate limit warnings (≥80% usage)
  - `provider_status_change` - Provider status change notifications
  - `ping` - Heartbeat to keep connections alive (every 30 seconds)

#### Connection Management:
- Auto-disconnect on errors
- Graceful connection cleanup
- Connection metadata tracking
- Client ID assignment

#### Background Tasks:
- Periodic broadcast loop (10-second intervals)
- Heartbeat loop (30-second intervals)
- Automatic rate limit monitoring
- Status update broadcasting

### 2. `/home/user/crypto-dt-source/api/endpoints.py` (NEW)
Comprehensive REST API endpoints with:

#### Endpoint Categories:

**Providers** (`/api/providers`)
- `GET /api/providers` - List all providers (with category filter)
- `GET /api/providers/{provider_name}` - Get specific provider
- `GET /api/providers/{provider_name}/stats` - Get provider statistics

**System Status** (`/api/status`)
- `GET /api/status` - Current system status
- `GET /api/status/metrics` - System metrics history

**Rate Limits** (`/api/rate-limits`)
- `GET /api/rate-limits` - All provider rate limits
- `GET /api/rate-limits/{provider_name}` - Specific provider rate limit

**Logs** (`/api/logs`)
- `GET /api/logs/{log_type}` - Get logs (connection, failure, collection, rate_limit)

**Alerts** (`/api/alerts`)
- `GET /api/alerts` - List alerts with filtering
- `POST /api/alerts/{alert_id}/acknowledge` - Acknowledge alert

**Scheduler** (`/api/scheduler`)
- `GET /api/scheduler/status` - Scheduler status
- `POST /api/scheduler/trigger/{job_id}` - Trigger job immediately

**Database** (`/api/database`)
- `GET /api/database/stats` - Database statistics
- `GET /api/database/health` - Database health check

**Analytics** (`/api/analytics`)
- `GET /api/analytics/failures` - Failure analysis

**Configuration** (`/api/config`)
- `GET /api/config/stats` - Configuration statistics

### 3. `/home/user/crypto-dt-source/app.py` (UPDATED)
Production-ready FastAPI application with:

#### Application Configuration:
- **Title**: Crypto API Monitoring System
- **Version**: 2.0.0
- **Host**: 0.0.0.0
- **Port**: 7860
- **Documentation**: Swagger UI at `/docs`, ReDoc at `/redoc`

#### Startup Sequence:
1. Initialize database (create tables)
2. Configure rate limiters for all providers
3. Populate database with provider configurations
4. Start WebSocket background tasks
5. Start task scheduler

#### Shutdown Sequence:
1. Stop task scheduler
2. Stop WebSocket background tasks
3. Close all WebSocket connections
4. Clean up resources

#### CORS Configuration:
- Allow all origins (configurable for production)
- Allow all methods
- Allow all headers
- Credentials enabled

#### Root Endpoints:
- `GET /` - API information and endpoint listing
- `GET /health` - Comprehensive health check
- `GET /info` - Detailed system information

#### Middleware:
- CORS middleware
- Global exception handler

## WebSocket Usage Example

### JavaScript Client:
```javascript
const ws = new WebSocket('ws://localhost:7860/ws/live');

ws.onopen = () => {
    console.log('Connected to WebSocket');
};

ws.onmessage = (event) => {
    const message = JSON.parse(event.data);

    switch(message.type) {
        case 'connection_established':
            console.log('Client ID:', message.client_id);
            break;

        case 'status_update':
            console.log('System Status:', message.system_metrics);
            break;

        case 'rate_limit_alert':
            console.warn(`Rate limit alert: ${message.provider} at ${message.percentage}%`);
            break;

        case 'provider_status_change':
            console.log(`Provider ${message.provider}: ${message.old_status} → ${message.new_status}`);
            break;

        case 'ping':
            // Respond with pong
            ws.send(JSON.stringify({ type: 'pong' }));
            break;
    }
};

ws.onclose = () => {
    console.log('Disconnected from WebSocket');
};

ws.onerror = (error) => {
    console.error('WebSocket error:', error);
};
```

### Python Client:
```python
import asyncio
import websockets
import json

async def websocket_client():
    uri = "ws://localhost:7860/ws/live"

    async with websockets.connect(uri) as websocket:
        while True:
            message = await websocket.recv()
            data = json.loads(message)

            if data['type'] == 'status_update':
                print(f"Status: {data['system_metrics']}")

            elif data['type'] == 'ping':
                # Respond with pong
                await websocket.send(json.dumps({'type': 'pong'}))

asyncio.run(websocket_client())
```

## REST API Usage Examples

### Get System Status:
```bash
curl http://localhost:7860/api/status
```

### Get All Providers:
```bash
curl http://localhost:7860/api/providers
```

### Get Provider Statistics:
```bash
curl http://localhost:7860/api/providers/CoinGecko/stats?hours=24
```

### Get Rate Limits:
```bash
curl http://localhost:7860/api/rate-limits
```

### Get Recent Logs:
```bash
curl "http://localhost:7860/api/logs/connection?hours=1&limit=100"
```

### Get Alerts:
```bash
curl "http://localhost:7860/api/alerts?acknowledged=false&hours=24"
```

### Acknowledge Alert:
```bash
curl -X POST http://localhost:7860/api/alerts/1/acknowledge
```

### Trigger Scheduler Job:
```bash
curl -X POST http://localhost:7860/api/scheduler/trigger/health_checks
```

## Running the Application

### Development:
```bash
cd /home/user/crypto-dt-source
python3 app.py
```

### Production (with Gunicorn):
```bash
gunicorn app:app -w 4 -k uvicorn.workers.UvicornWorker --bind 0.0.0.0:7860
```

### Docker:
```bash
docker build -t crypto-monitor .
docker run -p 7860:7860 crypto-monitor
```

## Testing

### Health Check:
```bash
curl http://localhost:7860/health
```

Expected response:
```json
{
  "status": "healthy",
  "timestamp": "2025-11-11T00:30:00.000000",
  "components": {
    "database": {"status": "healthy"},
    "scheduler": {"status": "running"},
    "websocket": {"status": "running", "active_connections": 0},
    "providers": {"total": 8, "online": 0, "degraded": 0, "offline": 0}
  }
}
```

### WebSocket Stats:
```bash
curl http://localhost:7860/ws/stats
```

### API Documentation:
Open browser to: http://localhost:7860/docs

## Features Implemented

### WebSocket Features:
✅ Real-time status updates (10-second intervals)
✅ Connection management (multiple clients)
✅ Heartbeat/ping-pong (30-second intervals)
✅ Auto-disconnect on errors
✅ Message broadcasting
✅ Client metadata tracking
✅ Background task management

### REST API Features:
✅ Provider management endpoints
✅ System status and metrics
✅ Rate limit monitoring
✅ Log retrieval (multiple types)
✅ Alert management
✅ Scheduler control
✅ Database statistics
✅ Failure analytics
✅ Configuration stats

### Application Features:
✅ FastAPI with full documentation
✅ CORS middleware (all origins)
✅ Database initialization on startup
✅ Rate limiter configuration
✅ Scheduler startup/shutdown
✅ WebSocket background tasks
✅ Graceful shutdown handling
✅ Global exception handling
✅ Comprehensive logging
✅ Health check endpoint
✅ System info endpoint

## Architecture

```
┌─────────────────────────────────────────────────────────────┐
│                     FastAPI Application                      │
│                      (app.py:7860)                          │
├─────────────────────────────────────────────────────────────┤
│                                                              │
│  ┌──────────────────┐  ┌───────────────────┐              │
│  │  REST API        │  │  WebSocket        │              │
│  │  /api/*          │  │  /ws/live         │              │
│  │  (endpoints.py)  │  │  (websocket.py)   │              │
│  └────────┬─────────┘  └─────────┬─────────┘              │
│           │                       │                         │
│           └───────────┬───────────┘                         │
│                       │                                     │
├───────────────────────┼─────────────────────────────────────┤
│                       ▼                                     │
│  ┌─────────────────────────────────────────────────────┐  │
│  │           Core Services Layer                        │  │
│  ├─────────────────────────────────────────────────────┤  │
│  │  • Database Manager (db_manager)                     │  │
│  │  • Task Scheduler (task_scheduler)                   │  │
│  │  • Rate Limiter (rate_limiter)                       │  │
│  │  • Configuration (config)                            │  │
│  │  • Health Checker (health_checker)                   │  │
│  └─────────────────────────────────────────────────────┘  │
│                       │                                     │
├───────────────────────┼─────────────────────────────────────┤
│                       ▼                                     │
│  ┌─────────────────────────────────────────────────────┐  │
│  │              Data Layer                              │  │
│  ├─────────────────────────────────────────────────────┤  │
│  │  • SQLite Database (data/api_monitor.db)            │  │
│  │  • Providers, Logs, Metrics, Alerts                 │  │
│  └─────────────────────────────────────────────────────┘  │
│                                                              │
└─────────────────────────────────────────────────────────────┘
```

## WebSocket Message Flow

```
Client                  Server                  Background Tasks
  │                       │                            │
  ├─────── Connect ──────>│                            │
  │<── connection_est. ───┤                            │
  │                       │                            │
  │                       │<──── Status Update ────────┤
  │<── status_update ─────┤      (10s interval)        │
  │                       │                            │
  │                       │<──── Heartbeat ────────────┤
  │<───── ping ───────────┤      (30s interval)        │
  ├────── pong ──────────>│                            │
  │                       │                            │
  │                       │<──── Rate Alert ───────────┤
  │<── rate_limit_alert ──┤      (when >80%)           │
  │                       │                            │
  │                       │<──── Provider Change ──────┤
  │<── provider_status ───┤      (on change)           │
  │                       │                            │
  ├──── Disconnect ──────>│                            │
  │                       │                            │
```

## Dependencies

All required packages are in `requirements.txt`:
- fastapi
- uvicorn[standard]
- websockets
- sqlalchemy
- apscheduler
- aiohttp
- python-dotenv

## Security Considerations

1. **CORS**: Currently set to allow all origins. In production, specify allowed origins:
   ```python
   allow_origins=["https://yourdomain.com"]
   ```

2. **API Keys**: Masked in responses using `_mask_key()` method

3. **Rate Limiting**: Built-in per-provider rate limiting

4. **WebSocket Authentication**: Can be added by implementing token validation in connection handler

5. **Database**: SQLite is suitable for development. Consider PostgreSQL for production.

## Monitoring & Observability

- **Logs**: Comprehensive logging via `utils.logger`
- **Health Checks**: `/health` endpoint with component status
- **Metrics**: System metrics tracked in database
- **Alerts**: Built-in alerting system
- **WebSocket Stats**: `/ws/stats` endpoint

## Next Steps (Optional Enhancements)

1. Add WebSocket authentication
2. Implement topic-based subscriptions
3. Add message queuing (Redis/RabbitMQ)
4. Implement horizontal scaling
5. Add Prometheus metrics export
6. Implement rate limiting per WebSocket client
7. Add message replay capability
8. Implement WebSocket reconnection logic
9. Add GraphQL API support
10. Implement API versioning

## Troubleshooting

### WebSocket won't connect:
- Check firewall settings
- Verify port 7860 is accessible
- Check CORS configuration

### Database errors:
- Ensure `data/` directory exists
- Check file permissions
- Verify SQLite is installed

### Scheduler not starting:
- Check database initialization
- Verify provider configurations
- Check logs for errors

### High memory usage:
- Limit number of WebSocket connections
- Implement connection pooling
- Adjust database cleanup settings

---

**Implementation Date**: 2025-11-11
**Version**: 2.0.0
**Status**: Production Ready ✅