GoJudge

GoJudge is a small programming contest management system written in Go.

Note

Please note, this project is mostly educational. If you really want to use it in production environment (i.e. running local programming contests) - use it at your own risk!

Goal of this project

Currently, there is no certain goal for it. I wanted to get experience using Go and at the same time was doing some contests on Codeforces (at which I am no very good by the way). So, I decided to make a Go web application for judging.

Getting Started

One of the things that I don't like in other contest systems is their installation. For example, ejudge requires Linux and compilation from scratch. It is also quite complex to configure. Another one, DOMJudge, which is used at ACM ICPC, needs some dependencies, like MySQL server and also Linux OS.

GoJudge tries to minimize effort needed to install and setup a working instance of GoJudge.

Pre-built binary

You can download GoJudge prebuilt binary in GitHub Releases page for your system. It includes GoJudge executable, Sandbox runner and starting directory structure.

Starting GoJudge is quite straightforward - just run gojudge main executable

cd gojudge
gojudge

Compiling from source

To compile and run from source, you will need Git and working Go installation.

git clone https://github.com/MrOnlineCoder/GoJudge.git
cd GoJudge
go get ./...
go build
gojudge

Usage

If GoJudge server has successfully started, open your favourite browser and browse to

http://localhost:1337

GoJudge client interface must open just for you.

GoJudge will create default administrator user on first run. Use it to log in and setup your contest.

Default administrator username: admin

Default administrator password: admin

Do not forget to change admin's password after successful login!

Features

Please note, not all features are well-tested and ready to use.

• No dependencies or third-party software needed for running
• Uses SQLite for storing all data
• Easy to use client interface built in Vue and Bootstrap
• Supports different methods for checking participants' solutions
• Runs submissions in a safe cross-platform sandbox environment
• Cross-platform: can run both on Windows and Linux

TODO

• Saving contest to a file (or DB)
• Scoreboard
• Handle contest end and results
• Jury user interface
• Realtime submission status update via WebSockets
• Clarifications
• Token based checking
• Checking using external checker program
• Configuration files
• Test on Linux
• Write sandbox runner for Linux
• Improve Windows sandbox by using access tokens
• Testing protocol

Architecture

• Web server: Golang net/http server with gorilla/mux router
• Web client: Vue.js SPA application
• Web UI: Bootstrap via Bootstrap-Vue
• Judging system: serveral worker goroutines, which receive incoming submission via channels

More on judging: GoJudge starts several worker goroutines (usually the number of workers equal the number of CPU cores on the machine). Each worker awaits for incoming submission and when one is avaliable, starts judging it. All commands are executed with os.Exec. Firstly, submission source code is written to a file in sandbox folder. Then, compiler is called to compile the submission. After that, compiled submission is ran through a set of tests, running via sandbox_runner each test. Final verdict is written to the database and source code and executable files for submission get deleted from sandbox folder.

Sandbox Security

All submissions executables are executed by sandbox_runner.

Sandbox Runner must do next things:

• Accept 3 arguments: path to exe timelimit, in ms memory limit, in KB
• Redirect own stdin/stdout to submission stdin/stdout
• Handle time limit: if programs runs longer than allowed, terminate it and return TIME_LIMIT_EXCEEDED verdict
• Handle memory limit
• Handle runtime error of the target executable
• Restrict program as much as possible - ideally allow it only to read stdin and write to stdout.
• If everything went OK, executable's stdout contents must be present in sandbox_runner stdout, runner must exit with code 0 (zero)
• If there was an internal error in sandbox_runner itself (i.e. syscall for executing submission executable failed), return verdict FAIL
• If any program limit was exceeded, return TIME_LIMIT_EXCEEDED or MEMORY_LIMIT_EXCEEDED respectively
• If there was a runtime error in target program, return RUNTIME_ERROR verdict
• Returning verdict means printing it in stderr and exiting with non-zero code (usually 1)

License

MIT (see LICENSE file)