On Jan 3, 2020, at 10:11, Miguel Ángel Prosper email@example.com wrote:
Having a way to clear the queue and then shutdown once existing jobs are done is a lot more manageable.
So the only clean way to do this is cooperative: flush the queue, send some kind of message to all children telling them to finish as quickly as possible, then wait for them to finish.
I was personally thinking of an implementation like that, cancel all still in pending and if wait is true the wait for the ones running, for both implementations.
OK, that makes sense. And it seems like it should be implementable; the only hard part is identifying all the edge cases and verifying they all do the right thing for both threads and processes.
But I don’t think “terminate” is the right name. Maybe “cancel”? Or even “shutdown(wait=whatever, cancel=True)?”
I think Java inspired this library, so maybe it’s worth looking at what they do. But IIRC, it’s a much more complicated API in general, and for this case you’d actually have to do something like this:
x.shutdown() # stop new submissions x.cancelAll() # cancel all tasks still in the queue x.purge() # remove and handle all canceled tasks x.join() # wait for already-started tasks to finish
… which probably isn’t what we want.
I didn't actually meant terminate literally, I just called it that as that's what multiprocessing.dummy.Pool.terminate (+ join after) does.
IIRC, it only does that by accident, because dummy.Process.terminate is a no-op, and that isn’t documented but just happens to be what CPython does.