codapi/docs/add-sandbox.md

Adding a sandbox

A sandbox is an isolated execution environment for running code snippets. A sandbox is typically implemented as one or more Docker containers. A sandbox supports at least one command (usually the run one), but it can support more (like test or any other).

Codapi comes with a single sh sandbox preinstalled, but you can easily add others. Let's see some examples.

Python

First, let's create a Docker image capable of running Python with some third-party packages:

cd /opt/codapi
mkdir images/python
touch images/python/Dockerfile
touch images/python/requirements.txt

Fill the Dockerfile:

FROM python:3.11-alpine

RUN adduser --home /sandbox --disabled-password sandbox

COPY requirements.txt /tmp
RUN pip install --no-cache-dir -r /tmp/requirements.txt && rm -f /tmp/requirements.txt

USER sandbox
WORKDIR /sandbox

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1

And the requirements.txt:

numpy==1.26.2
pandas==2.1.3

Build the image:

docker build --file images/python/Dockerfile --tag codapi/python:latest images/python/

And register the image as a Codapi box in boxes.json:

{
    // ...
    "python": {
        "image": "codapi/python"
    }
}

Finally, let's configure what happens when the client executes the run command in the python sandbox. To do this, we edit commands.json:

{
    // ...
    "python": {
        "run": {
            "engine": "docker",
            "entry": "main.py",
            "steps": [
                {
                    "box": "python",
                    "command": ["python", "main.py"]
                }
            ]
        }
    }
}

This is essentially what it says:

When the client executes the run command in the python sandbox, save their code to the main.py file, then run it in the python box (Docker container) using the python main.py shell command.

What if we want to add another command (say, test) to the same sandbox? Let's edit commands.json again:

{
    // ...
    "python": {
        "run": {
            // ...
        },
        "test": {
            "engine": "docker",
            "entry": "test_main.py",
            "steps": [
                {
                    "box": "python",
                    "command": ["python", "-m", "unittest"],
                    "noutput": 8192
                }
            ]
        }
    }
}

Besides configuring a different shell command, here we increased the maximum output size to 8Kb, as tests tend to be quite chatty (you can see the default value in config.json).

To apply the changed configuration, restart Codapi (as root):

systemctl restart codapi.service

And try running some Python code:

curl -H "content-type: application/json" -d '{ "sandbox": "python", "command": "run", "files": {"": "print(42)" }}' http://localhost:1313/v1/exec

Which produces the following output:

{
    "id": "python_run_7683de5a",
    "ok": true,
    "duration": 252,
    "stdout": "42\n",
    "stderr": ""
}