TypeError when connection is closed in connect()

I have the same problem then #185 but I think, I can reproduce it.

When you close a connection in the connect() method of a WebsocketConsumer, it works fine with daphne but uvicorn raises a TypeError

Traceback (most recent call last):
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/uvicorn/protocols/websockets/websockets_impl.py", line 140, in run_asgi
    result = await asgi(self.asgi_receive, self.asgi_send)
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/channels/sessions.py", line 179, in __call__
    return await self.inner(receive, self.send)
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/channels/middleware.py", line 41, in coroutine_call
    await inner_instance(receive, send)
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/channels/consumer.py", line 59, in __call__
    [receive, self.channel_receive], self.dispatch
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/channels/utils.py", line 59, in await_many_dispatch
    await task
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/channels/utils.py", line 51, in await_many_dispatch
    result = task.result()
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/uvicorn/protocols/websockets/websockets_impl.py", line 222, in asgi_receive
    data = await self.recv()
  File "/home/ossi/src/channels-examples/.venv/lib/python3.7/site-packages/websockets/protocol.py", line 419, in recv
    return_when=asyncio.FIRST_COMPLETED,
  File "/usr/lib/python3.7/asyncio/tasks.py", line 361, in wait
    fs = {ensure_future(f, loop=loop) for f in set(fs)}
  File "/usr/lib/python3.7/asyncio/tasks.py", line 361, in <setcomp>
    fs = {ensure_future(f, loop=loop) for f in set(fs)}
  File "/usr/lib/python3.7/asyncio/tasks.py", line 592, in ensure_future
    raise TypeError('An asyncio.Future, a coroutine or an awaitable is '
TypeError: An asyncio.Future, a coroutine or an awaitable is required

I created this branch on the django-channels-example repository: https://github.com/ostcar/channels-examples/tree/uvicorn-test

All I changed was, that the websocket connection is always closed: https://github.com/andrewgodwin/channels-examples/compare/master...ostcar:uvicorn-test

I think the problem is, that you call websockets.WebSocketServerProtocol.recv() before the websocket connection is open so websockets.WebSocketServerProtocol.connection_open() was not called. In this case the attribute transfer_data_task is still None. So when websockets.WebSocketServerProtocol.recv() calls

yield from asyncio.wait(
                    [pop_message_waiter, self.transfer_data_task],
                    loop=self.loop,
                    return_when=asyncio.FIRST_COMPLETED,
                )

it tries to await None what causes the exception.

I don’t know, if this is a but in the websockets package or if you should check self.closed before calling self.recv()

[adamhooper]

If anyone’s able to reduce the issue like that then I’d be very happy to dig into it.

@tomchristie ping? I have reduced the issue by enabling logging in Uvicorn’s own test suite. I also submitted pull request #704 with a sketch of a fix. Are you still keen to dig into it? 😃

[ostcar]

Here is a minimal example without using django:

class Application:
    def __init__(self, scope):
        self.scope = scope

    async def __call__(self, receive, send):
        if self.scope["type"] != "websocket":
            return

        while True:
            # what for the 'websocket.connect' event.
            await receive()

            # Close the connection
            await send({'type': 'websocket.close'})

To test it, you have to start it with an asgi server an open a websocket connection.

With daphne:

$ daphne asgi:Application
2019-04-13 23:49:51,867 INFO     Starting server at tcp:port=8000:interface=127.0.0.1
2019-04-13 23:49:51,867 INFO     HTTP/2 support not enabled (install the http2 and tls Twisted extras)
2019-04-13 23:49:51,867 INFO     Configuring endpoint tcp:port=8000:interface=127.0.0.1
2019-04-13 23:49:51,868 INFO     Listening on TCP address 127.0.0.1:8000
127.0.0.1:58152 - - [13/Apr/2019:23:50:00] "WSCONNECTING /" - -
127.0.0.1:58152 - - [13/Apr/2019:23:50:00] "WSREJECT /" - -
127.0.0.1:58152 - - [13/Apr/2019:23:50:00] "WSDISCONNECT /" - -
^C2019-04-13 23:50:01,841 INFO     Killed 1 pending application instances

With uvicorn and websockets:

$ uvicorn asgi:Application --ws websockets
INFO: Started server process [23052]
INFO: Waiting for application startup.
INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO: ('127.0.0.1', 58172) - "WebSocket /" 403
ERROR: Exception in ASGI application
Traceback (most recent call last):
  File "/home/ossi/src/uvicorn_test/venv/lib/python3.7/site-packages/uvicorn/protocols/websockets/websockets_impl.py", line 147, in run_asgi
    result = await asgi(self.asgi_receive, self.asgi_send)
  File "./asgi.py", line 12, in __call__
    await receive()
  File "/home/ossi/src/uvicorn_test/venv/lib/python3.7/site-packages/uvicorn/protocols/websockets/websockets_impl.py", line 227, in asgi_receive
    data = await self.recv()
  File "/home/ossi/src/uvicorn_test/venv/lib/python3.7/site-packages/websockets/protocol.py", line 419, in recv
    return_when=asyncio.FIRST_COMPLETED,
  File "/usr/lib/python3.7/asyncio/tasks.py", line 361, in wait
    fs = {ensure_future(f, loop=loop) for f in set(fs)}
  File "/usr/lib/python3.7/asyncio/tasks.py", line 361, in <setcomp>
    fs = {ensure_future(f, loop=loop) for f in set(fs)}
  File "/usr/lib/python3.7/asyncio/tasks.py", line 592, in ensure_future
    raise TypeError('An asyncio.Future, a coroutine or an awaitable is '
TypeError: An asyncio.Future, a coroutine or an awaitable is required
^CINFO: Shutting down
INFO: Waiting for application shutdown.
INFO: Finished server process [23052]

With uvicorn and wsproto:

$ uvicorn asgi:Application --ws wsproto
INFO: Started server process [23092]
INFO: Waiting for application startup.
INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO: ('127.0.0.1', 58178) - "WebSocket /" 403
ERROR: Exception in ASGI application
Traceback (most recent call last):
  File "/home/ossi/src/uvicorn_test/venv/lib/python3.7/site-packages/uvicorn/protocols/websockets/wsproto_impl.py", line 208, in run_asgi
    result = await asgi(self.receive, self.send)
  File "./asgi.py", line 15, in __call__
    await send({'type': 'websocket.close'})
  File "/home/ossi/src/uvicorn_test/venv/lib/python3.7/site-packages/uvicorn/protocols/websockets/wsproto_impl.py", line 257, in send
    output = self.conn.send(msg)
  File "/home/ossi/src/uvicorn_test/venv/lib/python3.7/site-packages/wsproto/__init__.py", line 35, in send
    data += self.handshake.send(event)
  File "/home/ossi/src/uvicorn_test/venv/lib/python3.7/site-packages/wsproto/handshake.py", line 97, in send
    "Event {} cannot be sent during the handshake".format(event)
wsproto.utilities.LocalProtocolError: Event Response(status_code=403, headers=[], http_version=b'1.1', reason=b'') cannot be sent during the handshake
^CINFO: Shutting down
INFO: Waiting for application shutdown.
INFO: Finished server process [23092]

The error seems to be, that the while True: loop does not break. But when I look into the django channels code, it seems, that django channels also does not close the loop.

The loop in django channels is here: https://github.com/django/channels/blob/03d221792e6881477911728615a6d51ec9fab73b/channels/utils.py#L45

The close message is send here: https://github.com/django/channels/blob/03d221792e6881477911728615a6d51ec9fab73b/channels/generic/websocket.py#L226

An exception, that could break the loop is raised when websocket.disconnect is handled: https://github.com/django/channels/blob/03d221792e6881477911728615a6d51ec9fab73b/channels/generic/websocket.py#L241