How to use loop.run_forever?

[jaklaassen-affirm]

Hi, this project is great! Thanks for putting it together.

I've been experimenting with running asyncio functions in gevent with loop.run_forever. I had trouble getting the asyncio loop to actually run any scheduled tasks because the event loop would never be notified when create_task is called because calling create_task does not notify selector.select. I was able to resolve this by making EventLoop.call_soon call self._write_to_self() in the same way that EventLoop.call_soon_threadsafe does, to notify the selector.

Something like this:

class GeventEventloop(asyncio.SelectorEventLoop):
    def __init__(self, selector=None):
        super(GeventEventloop, self).__init__(selector or gevent.selectors.DefaultSelector())

    def call_soon(self, callback, *args, context=None):
        handle = super(GeventEventloop, self).call_soon(callback, *args, context=context)
        self._write_to_self() # Without this, it never runs the task function
        return handle


loop = GeventEventloop()
loop_greenlet = gevent.spawn(loop.run_forever)
loop_greenlet.start()


async def logit(text):
    print(text)

def callit(fn, *args):
    task = loop.create_task(fn(*args))
    event = gevent.event.Event()
    def done(_):
        event.set()
    task.add_done_callback(done)
    event.wait()
    return task.result()

greenlets = []
for i in range(20):
    greenlets.append(gevent.spawn(callit, logit, "meow"))

gevent.wait(greenlets)

I'm curious if I'm doing something wrong, or if there is something useful to add to the framework or docs.