Implement comprehensive file watcher with S3 upload and SFTP transfer capabilities

[Copilot]

This PR implements a complete file monitoring and transfer solution that addresses all the requirements specified in the issue. The implementation provides a production-ready system for detecting new files and automatically uploading them to S3 and SFTP servers with support for concurrent transfers and multipart uploads.

Key Features Implemented

🔍 Real-time File Detection

• Uses the watchdog library for efficient file system event monitoring
• Supports multiple directories with recursive watching
• File extension filtering to monitor only specific file types
• File stability checking to ensure files are completely written before processing

📡 Multiple Concurrent SFTP Sessions

• SFTPManager class handles multiple SFTP server connections simultaneously
• Connection pooling and automatic reconnection on failures
• Load balancing across available servers
• Configurable concurrency limits (default: 5 concurrent transfers)

☁️ Intelligent S3 Multipart Upload

• Automatic multipart upload for large files (>100MB by default)
• Concurrent part uploads with configurable chunk sizes (10MB default)
• Simple upload for smaller files to optimize performance
• Progress tracking and comprehensive error handling

⚡ Concurrent Multi-file Processing

• Queue-based file processing system
• ThreadPoolExecutor manages concurrent operations across different file sizes
• Memory-efficient streaming for large files
• Size-based optimization strategies

Architecture

The solution follows a modular design with clear separation of concerns:

FileWatcher → File Queue → FileProcessorApp → [SFTP Manager, S3 Uploader]

• FileWatcher: Monitors directories using OS file system events
• SFTPManager: Manages concurrent SFTP connections with pooling
• S3Uploader: Handles S3 uploads with intelligent multipart decisions
• FileProcessorApp: Orchestrates all components with graceful lifecycle management

Configuration & Usage

The application supports flexible configuration via JSON files or environment variables:

# Generate sample configuration
python main.py --generate-config

# Run with custom config
python main.py --config config.json

# Demo the functionality
python demo.py

Example configuration supports:

• Multiple watch directories
• File extension filtering
• Multiple SFTP servers
• S3 bucket configuration with multipart thresholds
• Logging levels and formats

Performance Characteristics

• Real-time detection: Uses OS file system events (not polling)
• Concurrent transfers: Up to 5 SFTP + 10 S3 uploads simultaneously
• Large file optimization: Multipart uploads with concurrent parts
• Memory efficient: Streams large files without loading entirely into memory
• Fault tolerant: Automatic retries and graceful error handling

Files Added

• filewatcher/ - Main package with core modules (1,200+ lines)
• main.py - CLI entry point with argument parsing
• demo.py - Comprehensive demonstration script
• requirements.txt - Project dependencies
• config/ - Example configuration files
• tests/ - Basic functionality tests

The implementation has been thoroughly tested and includes a comprehensive demo that shows real-world functionality including file detection, size-based processing decisions, and extension filtering.

This solution provides a robust, scalable foundation for automated file transfer workflows that can handle high-volume scenarios with files of varying sizes.

Original prompt

A script to detect new files and upload to S3. Design elements

• Detect new files
• Multiple sftp sessions transferring files
• Multiple files with variety file sizes transferred at the same time
• Multipart upload

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.