Python+asyncio+autobahn websockets: CancelledError not bubbling up in the stack?

[karolyi]

Hey,

I have an asyncio-based websocket client implemented, with an onClose method:

    async def onClose(self, wasClean, code, reason):
        self.app.root.server_info.text = _(
            'Disconnected, reconnecting in 2 seconds')
        Logger.info(f'ServerTalker: Disconnected: {reason}')
        # Tasks in Tasks.all_tasks() are weakref's so this will get
        # garbage collected
        # self.factory.server_talker.transport = None
        try:
            await aiosleep(delay=5)
        except CancelledError:
            print('||| onClose CANCELLED')
            raise
        await self.factory.server_talker.create_server_connection()

Whenever I cancel the aiosleep from outside (aiosleep is just asyncio.sleep), it seems that the CancelledError raised at that point will get swallowed by some other part of the websocket client I don't have control over.

I get the debug from my print, but when I await the cancelled task to have it properly exited, the await takes forever, as if the CancelledError have been suppressed somewhere in the underlying code (not by me).

Could you please look into this?

[karolyi]

Alright, I might be wrong here. Asyncio is not well documented on how to deal with cancelled tasks.

After some googling, I found a locked issue comment that is talking about the exact same issue. That is:

• If you cancel a task, and don't catch the CancelledError, it SHOULD NOT be awaited
• If you cancel a task, but catch the CancelledError, it SHOULD be awaited otherwise one can get errors at shutdown (python exiting).