An Online Judging system (often shortened to OJ) is a tool used for programming competitions. It handles taking user submissions and… well… judging them. Usually this involves running the submission against a series of test cases.
This was a big undertaking for me as a project but overall I learned so much about many, many things from it. Some cool features include.
- WebSocket-based submission and feedback to users
- Fully customizable branding so the site can be customized for different schools / brands
- Git-based export of all problems for users, simply run
git cloneto get a copy of all your submissions! - From-scratch jailing system for running user code inside of, utilizing various Linux kernel features
- SAML integration so institutions can use their current auth instead of making users make new accounts
- Live updating leaderboard with animations for when teams change places
- Confetti :)
For the Git export I learned how Git worked at a low-level and re-implemented the “dumb” clone protocol in Rust, which involved creating a fake repo over HTTP.
For the jailing of user code I learned many parts of Linux process isolation. This was a very long process and arguably the most complex part of the site. I actually made a write-up on how the system works within the repo.
As of right now the system has not been integrated at my institution but the application code is done. In the future I want to add support for teams.