Cactus

Cactus is a programming contest hosting application. It is a single all-in-one binary that lets you host on-site programming contests over a local area network, with a web-based interface for managing problems, submissions, and standings.

Features

• Single binary with embedded web UI — no client installation needed
• Automatic judging with sandboxed code execution
• Support for C and C++ submissions
• Real-time updates via WebSocket
• Contest standings with scoring and penalty calculation
• Clarification (Q&A) system
• User management with participant, judge, and administrator roles
• CSV account import

Build

task

Usage

sudo ./cactus

Cactus requires sudo for sandboxing submitted code (when using the default ptrace jail). On first run, it creates a config.toml file that you can edit:

[core]
addr = ":5050"              # Server address

[belt]
size = 2                    # Number of concurrent judging workers

[sandbox]
# mode = "jail"             # Options: "jail" (ptrace, default), "docker"
# docker_image = "cactus-sandbox"

The web interface will be available at http://localhost:5050.

Docker Sandbox

To use Docker instead of the ptrace jail for sandboxing, first build the sandbox image:

task sandbox-image

Then set mode = "docker" under [sandbox] in config.toml. You can customize the image name with docker_image.

Why Cactus?

In 2014, I wanted to build an alternative to PC^2; a better way of hosting on-site programming contests over the local area network. Unlike PC^2, Cactus doesn't need a client to be installed on every computer. Cactus can be distributed as a single all-in-one binary.

Cactus served as my creative outlet until I started working on Toph.

License

Cactus is available under the BSD 3-Clause License.