docker-compose.yml

# The only containerised service is the Piston code-execution sandbox.
# The Next.js app and its SQLite database run natively on Node (npm run dev).
#
#   docker compose up -d               # start the judge
#   ./scripts/install-runtimes.sh      # one-time: install language runtimes
#   npm run dev                        # run the app on the host
#   curl localhost:3000/api/health     # verify app <-> db <-> piston
services:
  piston:
    image: ghcr.io/engineer-man/piston
    # Piston needs privileged mode for its sandbox isolation (nsjail).
    privileged: true
    environment:
      # Raise the per-run cap (default 3000ms) so per-problem time limits up to
      # 10s are honoured. The submit/run routes pass each problem's own limit.
      - PISTON_RUN_TIMEOUT=10000
      - PISTON_COMPILE_TIMEOUT=20000
      # Ceiling for per-run memory (512 MiB). The judge passes each problem's own
      # memory limit (default 256 MiB) per request, which must be <= this cap.
      - PISTON_RUN_MEMORY_LIMIT=536870912
    # Published on localhost so the Node app and the install script can reach it.
    ports:
      - "127.0.0.1:2000:2000"
    volumes:
      - piston-packages:/piston/packages
    tmpfs:
      - /tmp:exec
    restart: unless-stopped

volumes:
  piston-packages: