title: Is celery's apply_async thread or process?
body: <p>Can someone tell me whether Celery executes a task in a thread or in a separate child process? The documentation doesn't seem to explain it (read it like 3 times). If it is a thread, how does it get pass the GIL (particularly whom and how an event is notified)? </p>
  
  <p>How would you compare celery's async with Twisted's reactor model? Is celery using reactor model after all?</p>
  
  <p>Thanks,</p>