Blazer - Concurrent file downloader

A CLI tool to download files from anywhere concurrently using the power of go-routines written using stdlib without any dependencies.

Features

Control thread count
Resume from interruption
File integrity check - SHA256

Install

3 different ways:

go get -u github.com/arvryna/blazer
Download specific version from releases: https://github.com/arvryna/blazer/releases

Build from source:

git clone git@github.com:arvryna/blazer.git
make package

Usage

blazer -url=example.com/1.mp4 -t=10

Flags

blazer -h
Usage of blazer:
  -checksum string
        checksum SHA256(currently supported) to verify file
  -out string
        output path to store the downloaded file
  -t int
        Thread count - Number of concurrent downloads (default 10)
  -url string
        Valid URL to download
  -v    prints current version of blazer

Benchmarks

Name	Size	Blazer	cURL	Wget
Debian ISO	300 MB	1min 10 sec (25 threads)	2min 40 sec	3 min 10 sec
Windows-10	5.4 GB	20min 52sec (25 threads)	46min 52 sec	40 min 25 sec

Demo

Usage examples:

Integration with node.js server here

FAQ

How blazer works ?

Blazer makes use of RFC7233 to identify the size of the resource to download, and then initiates partial downloads concurrently with the help of multiple go-routines, once all segements are downloaded, we finally merge all the individual segments into the final file. Number of segments = thread count passed as param to blazer CLI

How file resumption work ?

If download is either interrupted manually or because of any network errors (Timeout RCP(connection reset by peer) - may happen if "-t" is a large number than server can handle) then those segments may fail and you may have to restart the download with same URL and thread count for retry to work because, temp folder name is a hash of URL and thread count.
When download is re-initiated, blazer downloads only the segments that were not successful during the previous attempt. Because a temproary download cache is stored in the current directory of download, which will be used to restart from where it was left off.
File resumption won't work if the number of threads used is different from the previous attempt.

Roadmap:

Possiblity of adding a config file for ~/.blazerc in home directory, to add new features like storing history of downloads
Ability to perform concurrent file uploads
Figuring out optimal thread count at runtime by considering various factors like network speed, server bandwidth, etc.,
Showing an interactive progress bar with higher accuracy
Add more algorithms for file integrity check

arvryna / blazer

readme