Long Polling flow

[qctan]

Hi @robertmrk

I'm trying using your library to receive notifications from a platform that only supports long-polling. I am rather new to Cometd but I did testing using the platform's example through Postman. It seems like the order of messages to set up that they are suggesting is /meta/handshake, /meta/subscribe, then /meta/connect, where the actual long-polling is held at the connect message until a notification is received.

However as I adapted your example to receive notifications from the platform, I can see the outgoing handshake message, followed by the incoming handshake message and finally the outgoing connect message where the long-polling is held. As the subscribe method is not
called until client is set up, I'm never able to receive any notification from the channel I'm interested in.

I am not sure if the order was defined in the protocol spec or whether there's something I've missed, but this is what I found in Salesforce's documentation (not the platform I'm referring to), where 'subscribe' happens before 'connect'.
https://developer.salesforce.com/docs/atlas.en-us.api_streaming.meta/api_streaming/using_streaming_api_client_connection.htm

Code:

async def chat():
    # connect to the server
    async with Client(f'https://platform.com/notifications', extensions=[MyExtension]) as client:
        
        await client.subscribe("/DecodedEventListener/trigger")
        
        # listen for incoming messages
        async for message in client:
            print(message)

Output:

Outgoing messages: [{'channel': <MetaChannel.HANDSHAKE: '/meta/handshake'>, 'version': '1.0', 'supportedConnectionTypes': ['websocket', 'long-polling'], 'minimumVersion': '1.0', 'id': '0'}]

response message: {'id': '0', 'minimumVersion': '1.0', 'supportedConnectionTypes': ['long-polling', 'smartrest-long-polling'], 'successful': True, 'channel': '/meta/handshake', 'ext': {'ack': True}, 'clientId': '2918jmzu83wu9gwi7av3thi1h5s', 'version': '1.0'}

Outgoing messages: [{'channel': <MetaChannel.CONNECT: '/meta/connect'>, 'clientId': '2918jmzu83wu9gwi7av3thi1h5s', 'connectionType': 'long-polling', 'id': '1'}]