[main] Long Tribler's shutdown

[drew2a]

Describe the bug
During the Tribler's shutdown, it freezes on this line:

tribler/src/tribler/core/components/restapi/rest/rest_manager.py

Line 169 in 4c7c3aa

await self.runner.cleanup() # self.site.stop() is called inside this method

To Reproduce
Steps to reproduce the behavior:

1. Open Tribler
2. Close Tribler

Screenshots

Additional context
The bug doesn't reproduce while running Tribler headless.

[drew2a]

Going deeper... The freeze happens here:

https://github.com/aio-libs/aiohttp/blob/3ff81dc9c9ce20efd3bf54cf52adaf438c483a92/aiohttp/web_protocol.py#L287-L288

                if self._task_handler is not None and not self._task_handler.done():
                    await self._task_handler

With the following value of self._task_handler:

Wait for  <Task pending name='Task-108' coro=<RequestHandler.start() running at /Users/<user>/Projects/github.com/Tribler/tribler/venv/lib/python3.9/site-packages/aiohttp/web_protocol.py:513>
wait_for=<Task pending name='Task-109' coro=<RequestHandler._handle_request() running at /Users/<user>/Projects/github.com/Tribler/tribler/venv/lib/python3.9/site-packages/aiohttp/web_protocol.py:434>
wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x10ec27a30>()]> cb=[<TaskWakeupMethWrapper object at 0x10eb73eb0>()]>>

[drew2a]

The bug started to appear after merge #7300

[kozlovsky]

As I understand it, the actual reason for the freezing is here:

class EventsEndpoint(RESTEndpoint):
    ...
    async def get_events(self, request):
        ...
        try:
            while True:
                await asyncio.sleep(3600)  # <-- here
        except CancelledError:
            self.events_responses.remove(response)
            return response

The EventsEndpoint response is a stream that never finishes. The response handling code even does not have a code path to finish the response during the shutdown. Also, the code eats and does not reraise the CancelledError exception, and that does not look good to me. I think the correct code should look like this:

class EventsEndpoint(RESTEndpoint):
    ...
    async def get_events(self, request):
        ...
        try:
            while not self._shutdown:
                await asyncio.sleep(1)
        finally:
            self.events_responses.remove(response)
        return response