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description: HTTP proxy and server patterns
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# HTTP Proxy and Server Patterns

## Request Handling
- Only support GET requests (Steam doesn't use other methods)
- Reject non-GET requests with 405 Method Not Allowed
- Handle health checks at "/" endpoint
- Support LanCache heartbeat at "/lancache-heartbeat"

## Upstream Communication
- Use optimized HTTP transport with connection pooling
- Set appropriate timeouts (10s dial, 15s header, 60s total)
- Enable HTTP/2 and keep-alives for better performance
- Use large buffers (64KB) for better throughput

## Response Streaming
- Stream responses directly to clients for better performance
- Support both full file and range request streaming
- Preserve original HTTP headers (excluding hop-by-hop headers)
- Add cache-specific headers (X-LanCache-Status, X-LanCache-Processed-By)

## Error Handling
- Implement retry logic with exponential backoff
- Handle upstream server errors gracefully
- Return appropriate HTTP status codes
- Log errors with sufficient context for debugging

## Concurrency Control
- Use semaphores to limit concurrent requests globally
- Implement per-client rate limiting
- Clean up old client limiters to prevent memory leaks
- Use proper synchronization for shared data structures

## Header Management
- Copy relevant headers from upstream responses
- Exclude hop-by-hop headers (Connection, Keep-Alive, etc.)
- Add cache status headers for monitoring
- Preserve Content-Type and Content-Length headers

## Client IP Detection
- Check X-Forwarded-For header first (for proxy setups)
- Fall back to X-Real-IP header
- Use RemoteAddr as final fallback
- Handle comma-separated IP lists in X-Forwarded-For

## Performance Optimizations
- Set keep-alive headers for better connection reuse
- Use appropriate server timeouts
- Implement request coalescing for duplicate requests
- Use buffered I/O for better performance

## Security Considerations
- Validate request URLs and paths
- Implement rate limiting to prevent abuse
- Log suspicious activity
- Handle malformed requests gracefully