How do I restart celery workers gracefully?

Question

While issuing a new build to update code in workers how do I restart celery workers gracefully?

Edit: What I intend to do is to something like this

Answer 1

What should happen to long running tasks? I like it this way: long running tasks should do their job. Don't interrupt them, only new tasks should get the new code.

But this is not possible at the moment: https://groups.google.com/d/msg/celery-users/uTalKMszT2Q/-MHleIY7WaIJ