Resource subclass and its init return value #663
Description
Hi there,
thanks a lot for this library and its great documentation! I could manage to port important parts of my application to using this, without any bigger issues.
One thing I had to spend some time for was the following.
Consider I subsclass a Resource, which creates a asyncio.Task, which should be cancelled on shutdown. I could not get this to work, except with this workaround:
class DispatcherQueueConsumerResource(resources.Resource): async def init(self, loop: AbstractEventLoop, disp, queue, **kwargs) -> Optional[Task]: t: Task = loop.create_task(disp.queue_consumer(queue)) # If this is an async method, we store the task to have that usable in `shutdown`. # # The `shutdown` method receives this method as an awaited coroutine and *not* the task we # just created and may return. Ergo does the cancellation not work, if we don't store our own # copy here. setattr(self, '__t', t) return async def shutdown(self, t: Task) -> None: to_cancel = None t_ = getattr(self, '__t', None) if t_: # Take `self.__t` with preference to_cancel = t_ elif t: to_cancel = t else: log.error("Nothing to shutdown: %s, %s", self, t) return try: if isinstance(to_cancel, Task): to_cancel_task = to_cancel elif inspect.iscoroutine(to_cancel): to_cancel_task = asyncio.create_task(to_cancel) else: raise RuntimeError(f"Don't know what I got here: {t}") was_cancelled = to_cancel_task.cancel() if was_cancelled: wait_for_seconds = 0.1 await asyncio.wait_for(to_cancel_task, wait_for_seconds) foo = 1 except AttributeError as e: log.error('Could not call `%s.cancel`: %s', to_cancel, e)As described in the init comment, we will receive a coroutine of DispatcherQueueConsumerResource.init as parameter in DispatcherQueueConsumerResource.shutdown, no matter what is returned from DispatcherQueueConsumerResource.init. It is hackable with this subclass solution, but not using the generator approach.
If I would be using the parameter t in shutdown, my code stalls forever when calling shutdown_resources. Therefore using the generator approach for my Resource is not working as is.
Just in case this is relevant, cause I saw this bug, I'm also using FastAPI in my application.
Please let me know if I should provide more information :)
Cheers!