HTTPStream.app_send is missing http.disconnect handling ?

tl;dr

I don’t see the code responsible for handling http.disconnect in http stream: https://github.com/pgjones/hypercorn/blob/8cef567301a5a3f4363d1c2cad76008e58add8aa/src/hypercorn/protocol/http_stream.py#L117-L177

It looks like an omission to me, especially given the websocket stream has code for handling it corresponding websocket.close

Long versions

I’ve written a simple middleware to simulate the asgi app being not responsive:

class AsgiOfflineMiddleware:

    def __init__(self, asgi_app):
        self.asgi_app = asgi_app
        self._offline_ports = set()
        self._offline_watchdogs_parking = trio.lowlevel.ParkingLot()

    @contextmanager
    def offline(self, port: int):
        assert port not in self._offline_ports
        self._offline_ports.add(port)
        self._offline_watchdogs_parking.unpark_all()
        try:
            yield
        finally:
            self._offline_ports.remove(port)
            # No need to unpark given our port has just been re-authorized !

    async def __call__(self, scope, receive, send):
        # Special case for lifespan given it corresponds to server init and not
        # to an incoming client connection
        if scope["type"] == "lifespan":
            return await self.asgi_app(scope, receive, send)

        port = scope["server"][1]

        pretend_to_be_offline = False

        if port in self._offline_ports:
            pretend_to_be_offline = True

        else:

            async def _offline_watchdog(cancel_scope):
                nonlocal pretend_to_be_offline
                while True:
                    await self._offline_watchdogs_parking.park()
                    if port in self._offline_ports:
                        break
                pretend_to_be_offline = True
                cancel_scope.cancel()

            async with trio.open_nursery() as nursery:
                nursery.start_soon(_offline_watchdog, nursery.cancel_scope)
                await self.asgi_app(scope, receive, send)
                nursery.cancel_scope.cancel()

        if pretend_to_be_offline:
            if scope["type"] == "http":
                await send({"type": "http.disconnect"})
            elif scope["type"] == "websocket":
                await send({"type": "websocket.close"})
            else:
                assert False, scope

However it produce errors when trying to close an HTTP connection:

ERROR    hypercorn.error:logging.py:100 Error in ASGI Framework
Traceback (most recent call last):
  File "C:\Users\gbleu\source\repos\parsec-cloud\venv39\lib\site-packages\hypercorn\trio\task_group.py", line 21, in _handle
    await invoke_asgi(app, scope, receive, send)
  File "C:\Users\gbleu\source\repos\parsec-cloud\venv39\lib\site-packages\hypercorn\utils.py", line 247, in invoke_asgi
    await app(scope, receive, send)
  File "C:\Users\gbleu\source\repos\parsec-cloud\parsec-cloud\tests\common\backend.py", line 427, in __call__
    await send({"type": "http.disconnect"})
  File "C:\Users\gbleu\source\repos\parsec-cloud\venv39\lib\site-packages\hypercorn\protocol\http_stream.py", line 177, in app_send
    raise UnexpectedMessageError(self.state, message["type"])
hypercorn.utils.UnexpectedMessageError: Unexpected message type, http.disconnect given the state ASGIHTTPState.REQUEST

[synodriver]

Hi. According to the spec, http.disconnect is an asgi receive event instead of send event, so you can not close the http connection in that way. Return 500 error would be ok.

[touilleMan]

thanks a lot @synodriver 😃 🎉

so it’s websocket.close that is the event the application send, and websocket.disconnect (and http.disconnect) that are send to the application !