channels: warnings/errors logged after disconnecting async http request

Hi,

I’m using version 2.1.1. I set up a simple consumer (almost the same as the SSE example from the docs). If I use runserver, and connect a client and then disconnect, some ugly logging occurs some time after.

10 seconds after disconnecting, there’s a warning:

2018-05-19 21:20:20,065 - WARNING - server - Application instance <Task pending coro=<AsyncHttpConsumer.__call__() running at /home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/channels/generic/http.py:25> wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x7fb79ead45b8>()]>> for connection <WebRequest at 0x7fb79fb2ff28 method=GET uri=/events/ clientproto=HTTP/1.1> took too long to shut down and was killed.

A client disconnecting from a stream is something I would consider to be normal behavior, and should probably not cause noisy logging.

60 seconds after disconnecting, there’s an exception:

Exception in callback AsyncioSelectorReactor.callLater.<locals>.run() at /home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/twisted/internet/asyncioreactor.py:287
handle: <TimerHandle when=275136.787314338 AsyncioSelectorReactor.callLater.<locals>.run() at /home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/twisted/internet/asyncioreactor.py:287>
Traceback (most recent call last):
  File "/usr/lib/python3.6/asyncio/events.py", line 145, in _run
    self._callback(*self._args)
  File "/home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/twisted/internet/asyncioreactor.py", line 290, in run
    f(*args, **kwargs)
  File "/home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/daphne/server.py", line 276, in timeout_checker
    protocol.check_timeouts()
  File "/home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/daphne/http_protocol.py", line 260, in check_timeouts
    self.basic_error(503, b"Service Unavailable", "Application failed to respond within time limit.")
  File "/home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/daphne/http_protocol.py", line 293, in basic_error
    (b"Content-Type", b"text/html; charset=utf-8"),
  File "/home/justin/dev/django-eventstream/examples/chat/venv3/lib/python3.6/site-packages/daphne/http_protocol.py", line 208, in handle_reply
    raise ValueError("HTTP response has already been started")
ValueError: HTTP response has already been started

That said, the warnings and errors appear to be harmless. New connections work as expected.

Here’s the consumer:

class EventsConsumer(AsyncHttpConsumer):
    async def handle(self, body):
        await self.send_headers(headers=[
	    ("Cache-Control", "no-cache"),
            ("Content-Type", "text/event-stream"),
        ])
        while True:
            payload = "data: %s\n\n" % datetime.now().isoformat()
            await self.send_body(payload.encode("utf-8"), more_body=True)
            await asyncio.sleep(1)