Parallel Downloader

DISCLAIMER: This project, including all code and documentation, was entirely generated by AI (Claude 3.7 Sonnet). It has not been manually reviewed, tested, or audited by a human. Use at your own risk.

A high-performance, concurrent file downloader written in Rust that splits downloads into multiple chunks and processes them in parallel to maximize bandwidth utilization.

Features

• HEAD Request Analysis: Automatically fetches file metadata without downloading content
• Parallel Downloading: Downloads file chunks concurrently to maximize throughput
• Progress Visualization: Real-time progress bars for overall download and individual chunks
• Resumable Downloads: Each chunk is tracked separately enabling potential resume capability
• Performance Metrics: Shows download speed and time upon completion
• Configurable Chunks: Adjust the number of parallel connections to optimize for your network

Installation

Prerequisites

• Rust and Cargo (1.60.0 or later recommended)
• An internet connection

Building from Source

1. Clone the repository:

   git clone https://github.com/yourusername/parallel-downloader.git
   cd parallel-downloader
   

2. Build the project:

   cargo build --release
   

3. The executable will be available at ./target/release/parallel-downloader

Usage

Basic Usage

parallel-downloader https://example.com/large-file.zip

With Options

parallel-downloader https://example.com/large-file.zip -o my-download.zip -c 20

Command-line Options

How It Works

1. Size Detection: Makes a HEAD request to determine the total file size
2. Chunking: Divides the file into equal-sized chunks based on the -c parameter
3. Parallel Processing: Creates async tasks for each chunk using Tokio
4. Range Requests: Uses HTTP Range headers to request specific byte ranges
5. Concurrent Writing: Each chunk writes to its designated position in the output file
6. Progress Tracking: Updates progress bars as chunks download

Performance Considerations

• More chunks aren't always better - there's a point of diminishing returns based on your connection and the server's capabilities
• Some servers may limit or reject parallel requests
• Best performance is usually achieved when chunk count is 2-4× the number of CPU cores

Limitations

• Some servers don't support range requests and will return the full file regardless
• Certain CDNs or servers may throttle or block parallel connections
• No support for authentication methods beyond what's in the URL
• No automatic retry mechanism for failed chunks

License

This project is available under the MIT License - see the LICENSE file for details.

Acknowledgements

• This code was generated entirely by Claude, an AI assistant by Anthropic
• Uses the following Rust crates:
  • reqwest: HTTP client
  • tokio: Async runtime
  • clap: Command-line argument parsing
  • indicatif: Progress bars
  • anyhow: Error handling