Sending data to Django channels

Question

I have an external Python script which generates JSON data every second; on the other side i have a Django application. I would like to stream that data on a webpage on my Django app. I already built a consumer with Django channels, but i don't know how to make Django have the data that i generate from the other Python script.

Here is my basic consumer:

class EchoConsumer(AsyncConsumer):
    async def websocket_connect(self, event):
        print("connected", event)


        await self.send({
            "type": "websocket.accept"
        })


    async def websocket_receive(self, event):
        print("received", event)
        # Echo the same received payload

    async def websocket_disconnect(self, event):
        print("disconnected", event)

Is there a specific way do this? Or am i supposed to use another service in the middle?Any advice is appreciated

Hasham Ghuffary · Accepted Answer · 2020-04-04 09:38:41Z

You can use the channel layer that is used to connect two or more 'Consumers' together. For example you want to build a chat room application and want multiple users in a room to send messages to each other in 'Realtime' you'd have to link then up using the channels layer.

    async def start_chat(self, event):
        auth_user = self.scope['user']
        data = event['data']
        recipient_user = data['recipient']

        self.chat_room = f'thread_{self.thread.id}'

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

    async def send_chat_message(self, event):
        message = await self.create_message_db(event.get('data'))
        message_data = MessageReadOnlySerializer(message).data

        # encoding the UUID object to json
        uid = message_data['sender']
        message_data['sender'] = json.loads(json.dumps(uid, cls=utlis.UUIDEncoder))

        await self.channel_layer.group_send(
            group=self.chat_room,
            message={
                'type': 'echo.message',
                'data': {
                    'message': message_data
                }

            }
        )

    async def echo_message(self, event):
        await self.send_json(event)

The code above is an example of how to use the channel layer. In the start_chat function, we are adding two consumers to a group this way we have established a path of communication between them so now when a consumer calls the send_chat_message it will call the echo_message function on both of the consumers.

I did not know about this use case. This could be what i'm looking for, thank you!

Hasham Ghuffary · Accepted Answer · 2020-04-03 09:46:18Z

0

What you could do is to pour that data to a DB model by using the @database_sync_to_async decorator. Take a look at the following example

 async def websocket_receive(self, event):
   message = await self.create_message_db(event.get('data'))

 @database_sync_to_async
  def create_message_db(self, data):
      return Message.objects.create(thread=self.thread, sender=self.scope['user'], 
             body=data['message'])

answered Apr 3, 2020 at 9:46

Hasham Ghuffary

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3 Comments

Sile Over a year ago

Hey, i considered updating it to a database, but since it's real time data and i would be uploading a lot of data every second, using a db would probably make me run into performance issues, so i can't use it for now

Hasham Ghuffary Over a year ago

@Sile well then you can use the channel layer to connect two or more consumers together.

Sile Over a year ago

Thanks for your answer! Can you please specify a little bit more about it?

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