CodeCamp

An online coding-judge platform: submit solutions to programming problems, have them compiled and run against test cases, and track results on contest leaderboards.

This is the API + frontend monorepo. The codebase was revamped in v2.0.0: boot-blocking bugs fixed, configuration centralised, secrets moved to the environment, and the code-execution judge rewritten in Go with OS-level sandboxing.

Architecture

 ┌─────────────────────────┐
Browser ──────────► │ Angular SPA │ (built into server/public)
└─────────────┬───────────┘
│ HTTP (REST + JWT)
┌─────────────▼───────────┐
│ API server (Node/Express) │ server/ · port 80
│ users, contests, problems, │
│ solutions, rankings │
└──────┬───────────────┬─────┘
│ HTTP │ Mongoose
GET /:id │ ▼
┌──────▼──────┐ ┌──────────┐
│ Judge (Go) │◄──┤ MongoDB │
│ judge/ │ │OnlineJudge│
│ port 3001 │ └──────────┘
│ gcc/g++/ │
│ javac/python│ (rlimit + timeout sandbox)
└─────────────┘

• server/ — Express API. Auth (JWT), contests, problems, solution submission, rankings. Serves the built SPA from server/public/.
• judge/ — Go service. Looks up a submission, compiles and runs it under CPU/memory/output/wall-clock limits, compares output to the expected file, and returns a verdict (true / false / "CE" / "TLE" / "RE").
• contest/ — shared Mongoose models (Contest, Problem, Ranking).
• codecamp-front/ — Angular SPA (single-page UI).

The server and judge share one MongoDB. The server writes test cases to judge/result/{input,output}/<contest>/<problem>.txt; the judge reads them.

Prerequisites

• Node.js 18+ and npm (API server + frontend)
• Go 1.21+ (judge service)
• MongoDB 4.x+ running locally (default mongodb://127.0.0.1:27017/OnlineJudge)
• Compilers/interpreters on PATH for the languages you want to judge: gcc, g++, javac/java, python3
• A Unix-like OS for the judge (Linux/macOS) — the sandbox uses POSIX setrlimit.

Setup

# 1. Configure
cp .env.example .env # then edit secrets / URIs# 2. Install API server deps
npm install
# 3. Build the frontend (outputs into server/public, served by the API)
npm run start:front

Environment variables (.env)

Variable	Purpose	Dev default
NODE_ENV	development / production	development
MONGODB_URI	Mongo connection (server + judge)	mongodb://127.0.0.1:27017/OnlineJudge
JWT_SECRET	JWT signing/verification secret	insecure dev fallback
SESSION_KEYS	comma-separated session keys	dev keys
PORT_SERVER	API server port	80
JUDGE_URL	where the server reaches the judge	http://localhost:3001
JUDGE_PORT	judge listen port	3001

In production the server refuses to start unless JWT_SECRET and SESSION_KEYS are set.

Running

npm run start:server # API server (Node)
npm run start:judge # judge service (Go) — cd judge && go run ./cmd/judge
npm start # both together (via concurrently)

Health checks: GET http://localhost:80/health and GET http://localhost:3001/health.

API (selected endpoints)

Method	Path	Description
GET	/health	liveness + DB status
POST	/users/signup	register (validated)
POST	/users/signin	login → JWT
GET	/users/profile	current user (JWT required)
POST	/contest	create contest
GET	/contest · /contest/:id	list / get contest
GET	/contest/:id/problems/:code	get problem
POST	/solution	submit a solution (validated)
GET	/solution/history/:username	paginated submission history
GET	/rankings/:contestId	contest leaderboard

The judge

Supported languages and their submission requirements:

Language	Aliases	Notes
C	c	compiled with gcc -O2
C++	cpp, c++	compiled with g++ -O2
Java	java	top-level class must be Main
Python	py, python, python3	run with python3

Each submission runs in a fresh temp directory with setrlimit caps on CPU time, memory, file-write size and open files, plus a wall-clock kill. The language and filenames come from a fixed allowlist and commands are executed via exec arg-slices (no shell), so submission data can never be injected into a shell command.

Testing

npm run lint # eslint over server/ + contest/ + scripts/
npm test# API smoke test (signup → signin → profile); SKIPs if no Mongocd judge && go vet ./... && go test ./... # judge unit tests

Known follow-ups (out of scope for the v2.0.0 revamp)

• Full Angular major-version upgrade (currently aligned on a self-consistent Angular 5 + CLI 1.7 toolchain).
• Container-per-submission isolation for the judge (current isolation is OS rlimits + timeout; a Docker seam is left for this).
• OAuth login strategies (passport providers were removed as dead code; auth is currently username/password + JWT).

License

MIT