# Nginx API Gateway Implementation Summary

**Status**: ✅ Complete
**Date**: 2026-01-30
**Version**: 1.0.0

## Overview

Production-ready Nginx API gateway for intelligent routing between Go (high-performance) and Python (AI/analytics) backends. Includes monitoring, caching, rate limiting, SSL/TLS, and comprehensive testing.

## Architecture

```
Internet/Clients
       │
       ▼
┌──────────────────────────────────────────────────┐
│              Nginx API Gateway                   │
│  • Intelligent routing (Go vs Python)           │
│  • Rate limiting (100 req/s API, 10 req/s AI)   │
│  • Caching (5min TTL for Go endpoints)          │
│  • SSL/TLS termination                          │
│  • Security headers (CORS, CSP, HSTS)           │
│  • Load balancing with health checks            │
└──────────────┬───────────────────┬───────────────┘
               │                   │
       ┌───────┴────────┐  ┌──────┴─────────┐
       ▼                │  │                ▼
┌─────────────┐         │  │      ┌─────────────┐
│ Go Backend  │         │  │      │   Python    │
│   :8080     │         │  │      │  Backend    │
│             │         │  │      │   :8000     │
│ • Items     │         │  │      │             │
│ • Links     │         │  │      │ • AI/LLM    │
│ • Projects  │         │  │      │ • Specs     │
│ • Graph     │         │  │      │ • Analytics │
│ • Search    │         │  │      │ • Execution │
│ • Webhooks  │         │  │      │ • Auth      │
│ • WebSocket │         │  │      │ • MCP       │
└──────┬──────┘         │  │      └──────┬──────┘
       │                │  │             │
       └────────────────┼──┼─────────────┘
                        ▼  ▼
                ┌──────────────────┐
                │   PostgreSQL     │
                │     Redis        │
                │      NATS        │
                └──────────────────┘
                        │
                        ▼
                ┌──────────────────┐
                │   Monitoring     │
                │  • Prometheus    │
                │  • Grafana       │
                │  • Exporters     │
                └──────────────────┘
```

## Files Created

### Nginx Configuration
1. **`/nginx/nginx.conf`** (Main config)
   - Worker processes: auto-detect
   - Connections: 4096 per worker
   - Gzip compression
   - Buffer optimization

2. **`/nginx/conf.d/tracertm.conf`** (Gateway routing)
   - Upstream definitions (Go, Python)
   - Rate limiting zones
   - Backend routing rules
   - Caching configuration
   - Health checks
   - WebSocket support
   - Security headers

3. **`/nginx/conf.d/ssl.conf`** (SSL/TLS config)
   - Modern cipher suites (TLS 1.2+)
   - OCSP stapling
   - HSTS headers
   - HTTP → HTTPS redirect

### Monitoring
4. **`/monitoring/prometheus.yml`**
   - Scrape configs for both backends
   - Nginx metrics (via exporter)
   - Database metrics
   - 15s scrape interval

5. **`/monitoring/dashboards/backend-comparison.json`**
   - Request rate comparison
   - Response time (p50, p95, p99)
   - Error rates by backend
   - Cache hit ratio
   - Resource usage

### Docker & Infrastructure
6. **`/docker-compose.yml`** (Production deployment)
   - Services: Nginx, Go, Python, Postgres, Redis, NATS
   - Exporters: Nginx, Postgres, Redis
   - Monitoring: Prometheus, Grafana
   - Health checks for all services
   - Proper dependencies

### Frontend Integration
7. **`/frontend/apps/web/src/api/client.ts`** (Updated)
   - API routing map (Go vs Python)
   - Development mode: direct backend routing
   - Production mode: Nginx handles routing
   - Automatic backend selection

### Documentation
8. **`/nginx/README.md`** (Comprehensive docs)
   - Architecture overview
   - Feature documentation
   - Setup guides (dev & prod)
   - Performance tuning
   - Troubleshooting

9. **`/GATEWAY_QUICK_START.md`** (Quick start)
   - 5-minute setup guide
   - Common tasks
   - Testing procedures
   - Production deployment

### Utilities
10. **`/scripts/test_gateway.sh`** (Test suite)
    - Health check tests
    - Backend routing tests
    - Rate limiting tests
    - Cache verification
    - Security headers check
    - Comprehensive reporting

11. **`/Makefile.gateway`** (Convenience commands)
    - `make start/stop/restart`
    - `make health/test/logs`
    - `make ssl-setup`
    - `make deploy`

12. **`/.env.gateway`** (Configuration template)
    - Database credentials
    - Grafana passwords
    - API keys
    - Log levels

## Routing Rules

### Python Backend Routes
```nginx
/api/v1/ai/*               → python:8000
/api/v1/specifications/*   → python:8000
/api/v1/spec-analytics/*   → python:8000
/api/v1/execution/*        → python:8000
/api/v1/hatchet/*          → python:8000
/api/v1/chaos/*            → python:8000
/api/v1/mcp/*              → python:8000
/api/v1/recording/*        → python:8000
/api/v1/blockchain/*       → python:8000
/api/v1/auth/*             → python:8000
```

**Characteristics**:
- Rate limit: 10 req/s (AI operations)
- No caching (dynamic content)
- Long timeout: 600s (AI processing)
- Buffering disabled (streaming responses)

### Go Backend Routes
```nginx
/api/v1/items/*            → go:8080
/api/v1/links/*            → go:8080
/api/v1/projects/*         → go:8080
/api/v1/graph/*            → go:8080
/api/v1/bulk/*             → go:8080
/api/v1/search/*           → go:8080
/api/v1/export/*           → go:8080
/api/v1/import/*           → go:8080
/api/v1/webhooks/*         → go:8080
/api/v1/traceability/*     → go:8080
/ws                        → go:8080 (WebSocket)
```

**Characteristics**:
- Rate limit: 100 req/s (high throughput)
- Caching: 5min TTL for GET requests
- Standard timeout: 300s
- Connection pooling: 64 keepalive

## Key Features

### 1. Intelligent Routing
- Path-based routing to appropriate backend
- Automatic failover on health check failure
- Keepalive connections (32 Python, 64 Go)
- 3 max failures, 30s timeout

### 2. Rate Limiting
- **API endpoints**: 100 req/s, burst 50
- **AI endpoints**: 10 req/s, burst 20
- **Connections**: 50 concurrent per IP
- Zone size: 10MB (tracks ~160k IPs)

### 3. Caching
- **Go backend GET requests**: 5min TTL
- **Cache size**: 1GB max
- **Cache key**: `$request_uri|$request_body`
- **Headers**: X-Cache-Status (HIT/MISS/BYPASS)
- **Inactive eviction**: 60min

### 4. Security
- **Headers**: X-Frame-Options, X-Content-Type-Options, X-XSS-Protection
- **CORS**: Configurable origins, credentials support
- **SSL/TLS**: TLS 1.2+, modern ciphers
- **HSTS**: 2 years max-age
- **CSP**: Configurable Content Security Policy

### 5. WebSocket Support
- Dedicated `/ws` endpoint to Go backend
- Long timeout: 24 hours
- Buffering disabled
- Upgrade header handling

### 6. Monitoring
- **Prometheus metrics**: Both backends + Nginx
- **Grafana dashboards**: Performance comparison
- **Exporters**: Nginx, Postgres, Redis
- **Access logs**: Custom format with timing

### 7. Health Checks
- `/health` - Main gateway (→ Go)
- `/health/go` - Go backend health
- `/health/python` - Python backend health
- Docker health checks for all services

## Performance Benchmarks

### Expected Performance
| Metric | Go Backend | Python Backend |
|--------|-----------|----------------|
| Throughput | 5,000+ req/s | 500-1,000 req/s |
| Latency (p50) | <10ms | <50ms |
| Latency (p95) | <50ms | <200ms |
| Cache hit rate | 70-90% | N/A |
| Concurrent conns | 10,000+ | 1,000+ |

### Resource Usage
| Service | CPU | Memory |
|---------|-----|--------|
| Nginx | <5% | 50MB |
| Go Backend | 10-30% | 200MB |
| Python Backend | 30-60% | 500MB |
| PostgreSQL | 10-20% | 500MB |
| Redis | <5% | 100MB |

## Testing

### Automated Test Suite
```bash
./scripts/test_gateway.sh
```

Tests performed:
1. Health checks (main, Go, Python)
2. Go backend routing (items, links, projects, graph, search)
3. Python backend routing (AI, specs, auth)
4. WebSocket connection
5. Rate limiting (110 requests)
6. Cache headers (X-Cache-Status)
7. CORS headers
8. Security headers

### Manual Testing
```bash
# Health
curl http://localhost/health

# Go backend
curl http://localhost/api/v1/items

# Python backend
curl http://localhost/api/v1/ai/health

# WebSocket
wscat -c ws://localhost/ws

# Rate limit
for i in {1..110}; do curl http://localhost/api/v1/items; done

# Cache
curl -I http://localhost/api/v1/items  # MISS
curl -I http://localhost/api/v1/items  # HIT
```

## Deployment

### Development
```bash
make setup        # Initial setup
make start        # Start services
make health       # Check health
make test         # Run tests
make logs         # View logs
```

### Production
```bash
# 1. Configure environment
cp .env.gateway .env
# Edit .env with production values

# 2. Set up SSL
make ssl-setup

# 3. Deploy
make deploy

# 4. Verify
make health
make test
```

### Monitoring Access
- **Grafana**: http://localhost:3000 (admin/admin)
- **Prometheus**: http://localhost:9090
- **Nginx metrics**: http://localhost/metrics (internal only)

## Configuration Tuning

### High-Traffic Sites
```nginx
# nginx.conf
worker_processes auto;
worker_connections 8192;

# tracertm.conf
limit_req_zone ... rate=500r/s;  # Increase rate limit
proxy_cache_path ... max_size=10g;  # Larger cache
```

### AI-Heavy Workloads
```nginx
# tracertm.conf
location ~ ^/api/v1/ai/ {
    limit_req zone=ai_limit burst=50;  # More burst
    proxy_read_timeout 1800s;  # 30min timeout
}
```

### Low-Latency Requirements
```nginx
# tracertm.conf
proxy_cache_valid 200 1m;  # Shorter cache TTL
keepalive 128;  # More keepalive connections
```

## Troubleshooting Guide

### 502 Bad Gateway
```bash
# Check backend health
docker-compose ps
docker-compose logs go-backend python-backend

# Verify network
docker-compose exec nginx ping go-backend
```

### High Memory Usage
```bash
# Check stats
docker stats

# Adjust cache
# Edit nginx/conf.d/tracertm.conf
proxy_cache_path ... max_size=500m;  # Reduce cache
```

### Slow Responses
```bash
# Check Grafana dashboards
# Look at response time by backend

# Identify bottleneck
docker-compose logs -f python-backend  # If Python slow
docker-compose logs -f postgres  # If database slow
```

### Cache Not Working
```bash
# Verify cache directory
docker-compose exec nginx ls -la /var/cache/nginx/

# Check headers
curl -I http://localhost/api/v1/items

# Clear cache
make cache-clear
```

## Security Considerations

1. **SSL/TLS in Production**
   - Use Let's Encrypt or valid certificates
   - Enable HSTS
   - Force HTTPS redirect

2. **Rate Limiting**
   - Tune based on expected traffic
   - Use different zones for different endpoints
   - Monitor for abuse

3. **CORS**
   - Restrict origins in production
   - Don't use `*` wildcard
   - Validate credentials

4. **Database**
   - Strong passwords
   - Limited user permissions
   - Regular backups

5. **Monitoring**
   - Restrict Grafana/Prometheus access
   - Use strong passwords
   - Enable authentication

## Maintenance

### Daily
- Monitor Grafana dashboards
- Check error rates
- Review access logs

### Weekly
- Database backups: `make db-backup`
- Review resource usage: `make stats`
- Update dependencies

### Monthly
- SSL certificate renewal (auto with Let's Encrypt)
- Review and tune rate limits
- Analyze cache hit rates
- Security updates

## Future Enhancements

1. **Auto-scaling**
   - Kubernetes deployment
   - Horizontal pod autoscaling
   - Dynamic rate limits

2. **Advanced Caching**
   - Redis-based cache
   - Cache warming
   - Intelligent invalidation

3. **Better Observability**
   - Distributed tracing (Jaeger)
   - ELK stack integration
   - APM tools

4. **HA & Failover**
   - Multiple Nginx instances
   - Database replication
   - Redis clustering

5. **Edge Computing**
   - CDN integration
   - Global load balancing
   - Regional backends

## Success Metrics

✅ **Completed**:
- [x] Nginx routing configuration
- [x] Rate limiting implementation
- [x] Caching for Go endpoints
- [x] SSL/TLS support
- [x] WebSocket routing
- [x] Health checks (all backends)
- [x] Prometheus monitoring
- [x] Grafana dashboards
- [x] Frontend client integration
- [x] Comprehensive testing
- [x] Documentation
- [x] Docker Compose setup

✅ **Verified**:
- [x] Routing works for both backends
- [x] Rate limits enforced
- [x] Cache hit rate >0%
- [x] Health checks passing
- [x] Monitoring data flowing
- [x] Test suite passes
- [x] Documentation complete

## Quick Reference

### Start/Stop
```bash
make start        # Start all services
make stop         # Stop all services
make restart      # Restart all services
```

### Monitoring
```bash
make health       # Check health
make test         # Run tests
make logs         # View logs
make stats        # Resource usage
```

### Configuration
```bash
make config-test  # Test Nginx config
make config-reload # Reload Nginx
make cache-clear  # Clear cache
```

### Production
```bash
make ssl-setup    # Set up SSL
make deploy       # Production deploy
make db-backup    # Backup database
```

## Support

- **Documentation**: `/nginx/README.md`
- **Quick Start**: `/GATEWAY_QUICK_START.md`
- **Test Suite**: `./scripts/test_gateway.sh`
- **Makefile**: `make help`

## License

Proprietary - TracerTM
Version: 1.0.0
Date: 2026-01-30
