Multi-Get Coding Challenge

Task

Build an application that downloads part of a file from a web server, in chunks.

This is a simplified version of a “download booster”, which speeds up downloads by requesting files in multiple pieces simultaneously (saturating the network), then reassembling the pieces.

Installation and Usage

$ mvn clean install 

## View usage information
$ java -jar multiget.jar --help

usage: java -jar multiget.jar <URL> [OPTIONS]
Download part of a file in chunks

 -c,--chunks <arg>   number of chunks to download
 -f,--file <arg>     name of the file to output
 -h,--help           print help message
 -p,--parallel       download the chunks in parallel
 -s,--size <arg>     size of the chunks to download

Please report issues at https://github.com/elainaRenee/multi-get/issues

Exit Codes

-1 - Invalid argument
 0 - Success
 1 - Fail

Testing

$ mvn clean test

Requirements

• Source URL should be specified with a required command-line option
• File is downloaded in 4 chunks (4 requests made to the server)
• Only the first 4 MiB of the file should be downloaded from the server
• Output file may be specified with a command-line option (but may have a default if not set)
• No corruption in file - correct order, correct size, correct bytes (you don’t need to verify correctness, but it should not introduce errors)
• File is retrieved with GET requests

Optional features

• File is downloaded in parallel rather than serial
• Support files smaller than 4 MiB (less chunks/adjust chunk size)
• Configurable number of chunks/chunk size/total download size

Out of scope

• HTTPS
• Server doesn’t support range request, or serves it incorrectly
• Other HTTP methods (PUT/POST/DELETE)
• Re-use existing connections with HTTP keep-alive

Additional notes

• You may use any system or open-source libraries you need to perform this task
• You can assume the test file will be bigger than the test size (> 4 MiB)
• Document your assumptions if this document is unclear and they affect your design