Django Channels Error: you cannot use AsyncToSync in the same thread as an async event loop

Question

I was trying to copy the tutorial in Django Channels Documentation. But I'm having errors. It says

You cannot use AsyncToSync in the same thread as an async event loop - just await the async function directly.

INFO WebSocket HANDSHAKING /ws/notifications/app/98578113-89e9-4465-ab37-e8b4d89450c2/ [127.0.0.1:57302]

Exception inside application: You cannot use AsyncToSync in the same thread as an async event loop - just await the async function directly.

File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/channels/consumer.py", line 59, in call [receive, self.channel_receive], self.dispatch

File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/channels/utils.py", line 51, in await_many_dispatch await dispatch(result)

File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/channels/consumer.py", line 73, in dispatch await handler(message)

File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/channels/generic/websocket.py", line 175, in websocket_connect await self.connect()

File "/Users/goutambseervi/PycharmProjects/cilliai-backend/api/notifications/consumers.py", line 51, in connect self.channel_name

File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/asgiref/sync.py", line 62, in call "You cannot use AsyncToSync in the same thread as an async event loop - "

You cannot use AsyncToSync in the same thread as an async event loop - just await the async function directly.

Here is the consumer:

class AppConsumer(AsyncWebsocketConsumer):
    async def connect(self):
        self.room_name = self.scope['url_route']['kwargs']['user_id']
        self.room_group_name = 'chat_%s' % self.room_name

        await async_to_sync(self.channel_layer.group_add)(
            self.room_group_name,
            self.channel_name
        )
        await self.accept()

    async def disconnect(self, code):
        await async_to_sync(self.channel_layer.group_discard)(
            self.room_group_name,
            self.channel_name
        )

    async def receive(self, text_data=None, bytes_data=None):
        text_data_json = json.loads(text_data)
        message = text_data_json['message']

        await self.channel_layer.group_send(
            self.room_group_name,
            {
                'type': 'chat_message',
                'message': message
            }
        )

    async def send_message(self, event):
        message = event['message']

        await self.send(text_data=json.dumps({
            'message': message
        }))

Aprimus Aprimus · Accepted Answer · 2019-12-08T05:09:26

I think you need to replace this calls:

 await async_to_sync(self.channel_layer.group_add)(
        self.room_group_name,
        self.channel_name
    )

await async_to_sync(self.channel_layer.group_discard)(
        self.room_group_name,
        self.channel_name
    )

with this just await:

await self.channel_layer.group_add(
        self.room_group_name,
        self.channel_name
    )

await self.channel_layer.group_discard(
        self.room_group_name,
        self.channel_name
    )

Django Channels Error: you cannot use AsyncToSync in the same thread as an async event loop

1 Answers