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🎉 Codespaces

I was curious about how Codeforces worked, so I created my own version!
Welcome to Codespaces — your social problem-solving playground! 🧑‍💻✨

✨ Features

  • ✏️ Create Your Own Problems: Feeling creative? You can also create and manage your own coding problems! 🎨
  • 🔍 Codeforces Problem Scraping: Enter a Codeforces problem link and watch the magic happen! The problem statement and test cases are automatically parsed and shared across all users in the room. 🌟
  • 🚀 Code Evaluation: Evaluate code submissions on the fly in a safe and secure sandboxed environment!
  • 👩‍💻 Collaborative Coding: Team up with your friends and solve problems together in real-time with up to 10 users.
  • 🎤 Group Voice Chat: Integrated group voice chat for seamless collaboration using WebRTC.
  • 📦 Problem Packages: Easily store and manage problem packages.
  • 🧮🖼️ Math & Image Rendering: Supports rendering math equations and images in problem statements.
  • ⚡ Caching: Lightning-fast caching for problem statements and packages using Redis.

Can even be used to host contests completely locally (for the most part).

🎬 Demo

Check out the demo here 🍿
(Hosting is currently down as I lost access to my EC2 instance 😢)

🏗️ System Architecture

High-Level

A (not-so-)little monolithic system that handles everything from scraping to collaborative coding.

Submission Handling

  1. Backend pulls test data from the database (or cache if available).
  2. Every new submission triggers a Docker container (Alpine Linux).
  3. Container compiles and runs the code in a sandbox:
    • 2-second time limit
    • 256 MB memory limit
    • No internet access
    • Max 100 processes (to avoid fork bombs)

🐳 Inside the Container

Steps performed:

  1. Compile code and put it in a sandboxed environment with the input data.
  2. Randomly change the root password to prevent access.
  3. Lock environment so code can’t access anything outside its sandbox.
  4. Run code with a 2-second time limit.
  5. Compare program output to expected output, return verdict.

🔧 Implementation Details

  • 🎤 Group Voice Chat: WebRTC
  • 🐳 Docker API: Spawn containers for code evaluation
  • 🤝 Collaboration: Socket.IO for real-time coding
  • ⛏ Web Scraping: BeautifulSoup custom scraper for Codeforces
  • 🏖 Sandboxing: Non-privileged users inside Docker
  • 📦 Problem Packages: Stored in MongoDB
  • ⚡ Redis Caching: Cache problem packages & test data
  • 🧮 Math Rendering: KaTeX
  • 🚫 Rate Limiting: Added to compilation API

Supported Languages: C++ only for now.

🎯 Current Objectives

  • Make the submission system more scalable & efficient (possibly microservice).
  • Multi-node setup using free-tier EC2 + Kubernetes auto-scaling.
  • Fix recent security issue related to compiling untrusted code.

🚀 Usage

Prerequisites: Docker & Redis installed in backend.

# Clone repository
git clone https://github.com/nubskr/codespace.git
cd codespace

# Install dependencies
npm install

# Pull container images & setup environment variables
sudo ./setup.sh
cd ./server
vim .env

# Example .env
MONGODB_URI=''
AWS_ACCESS_KEY_ID=''
AWS_SECRET_ACCESS_KEY=''
AWS_REGION=''
S3_BUCKET_NAME=''
CONCURRENT_SCRAPING_WORKERS=''
CONCURRENT_SUBMISSION_WORKERS=''

# Start backend
npm start

# Start frontend
cd ..
cd ./frontend
npm start