how to run python script with os.fork on windows?

Question

os.fork() command is not supported under windows, and gives the following error:

AttributeError: 'module' object has no attribute 'fork'

So the general question is How to run a script that contain a call to os.fork() under Windows?. I don't mind using something that only mocks up the behavior and runs much slower, it's only for testing. I also prefer not to change the script as it is a 3rd party module.

To give you a wider perspective, I'm trying to use the module rq a.k.a redis queue on Windows. Eventually I will run the code on heroku server which is a Linux machine, but during the development of the web app I'm using Windows.

Answer 1

There is no easy way to emulate fork() on systems that don't have it, such as Windows. If the code only uses fork() to start a new process with exec, you can port it to use subprocess. But this doesn't appear to be the case in rq, so you have several options:

1. Port rq to Windows, or ask someone to do it for you. The easiest way to port the part of the code that calls fork() might be by using the multiprocessing module. However, you will still need to replace other parts of the code that depend on Unix, such as uses of signal.alarm() in the timeouts module.

2. Use Python under Cygwin, which emulates a fully functional (though slowish) fork(), so Cygwin Python has a working os.fork(). Note that to get os.fork(), you will need to use a Cygwin-built Python, such as the one that Cygwin ships, and not simply run the normal Windows Python under Cygwin.

3. Test the application on a Linux running in a virtual machine.

Among these unhappy options I'd recommend the last one.