How can I use pysandbox in a Django request handler?

Question

I want to use pysandbox to allow users to run code on my server. I'm using Django's internal server (manage.py runserver) with this request handler:

def try_sandbox(request):
    from sandbox import Sandbox
    def func(a, b):
        return a + b
    sandbox = Sandbox()
    result = sandbox.call(func, 1, 2)
    return HttpResponse(result)

When accessing the page I get a ValueError:

Request Method: GET
Exception Type: ValueError
Exception Value:   signal only works in main thread
Exception Location: /Library/Python/2.7/site-packages/sandbox/timeout.py in limitedTime, line 45
Python Executable:  /usr/bin/python

Traceback:

Django Version: 1.3.1
Python Version: 2.7.1
File "[...]views.py" in try_sandbox
  77.     result = sandbox.call(func, 1, 2)
File "/Library/Python/2.7/site-packages/sandbox/sandbox_class.py" in call
  44.         return self._call(func, args, kw)
File "/Library/Python/2.7/site-packages/sandbox/sandbox_class.py" in _call
  31.                 return limitedTime(timeout, func, *args, **kw)
File "/Library/Python/2.7/site-packages/sandbox/timeout.py" in limitedTime
  45.             old_alarm = signal(SIGALRM, signalHandler)

Is it possible to use pysandbox in this environment?

(I'm think I'm using pysandbox 1.1 - that's what the version.py in the download says. The download folder says 1.0.1. I'm running Mac OS 10.7.2.)

Answer 1

I've not encountered this error myself so I may be absolutely wrong - but it seems like if pysandbox doesn't like running on non-main threads then you should ensure that it is running on the main thread. If you look at the django runserver documentation, it seems that a --nothreading option has been introduced in the development version of django. If this is what you're running, then it may be worth checking out. For example:

manage.py runserver --nothreading

Alternatively, if you still can't get it working (and don't mind that this idea is probably very inefficient) you could spawn off a separate process using subprocess.check_output or similar, and run your sandboxed code from there. This really isn't a brilliant idea for various reasons, but would definitely cause the sandbox code to be run from a main thread.