Django Channels and WebSocket Routing and URL Parameters

[Robert Roskam]

It seems like passing parameters through routing for websockets should be something that we want, but I've been surprised that I've seen absolutely 0 comments or questions on this so far.

What am I saying specifically? Let me show you from the popular article that jacobian wrote up on Heroku's blog:

https://blog.heroku.com/in_deep_with_django_channels_the_future_of_real_time_apps_in_django 

____

Need to hook each of these channels up in routing.py:

from . import consumers

channel_routing = {
    'websocket.connect': consumers.ws_connect,
    'websocket.receive': consumers.ws_receive,
    'websocket.disconnect': consumers.ws_disconnect,
}

Pretty simple stuff: just connect each channel to an appropriate function. Now, let’s look at those functions. By convention we’ll put these functions in aconsumers.py (but, like views, these could be anywhere.)

Let’s look at ws_connect first:

from channels import Group
from channels.sessions import channel_session
from .models import Room

@channel_session
def ws_connect(message):
    prefix, label = message['path'].strip('/').split('/')
    room = Room.objects.get(label=label)
    Group('chat-' + label).add(message.reply_channel)
    message.channel_session['room'] = room.label

___

So everything above is straight from that article. I'd like to focus in on this line:

prefix, label = message['path'].strip('/').split('/').

It seems like this should not be tightly coupled to this consumer. It seems like this should be handled more like this:

from channels.urls import parameters  # I know this doesn't exist
from. import consumers 

channel_routing = {
    parameters('websocket.connect', consumers.ws_connect, path=r'chat/(?P<label>\w+)',
    'websocket.receive': consumers.ws_receive,
   'websocket.disconnect': consumers.ws_disconnect,
}

Then you would be able to consume the result this way:

from channels import Group
from channels.sessions import channel_session
from .models import Room

@channel_session
def ws_connect(message, *args, **kwrags):
    label = kwargs['label']
    room = Room.objects.get(label=label)
    Group('chat-' + label).add(message.reply_channel)
    message.channel_session['room'] = room.label

Thoughts?

[Andrew Godwin]

Hi Robert,

That blog post dates from before the URL/parameter matching in channels. You can now do things like this:

chat_routing = [

    route("websocket.connect", chat_connect, path=r"^/(?P<room>[a-zA-Z0-9_]+)/$),

    route("websocket.disconnect", chat_disconnect),

]

routing = [

    # You can use a string import path as the first argument as well.

    include(chat_routing, path=r"^/chat"),

]

You can read more in the docs here: http://channels.readthedocs.io/en/latest/getting-started.html#routing

Andrew

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[Robert Roskam]

Awesome! I was looking for this way back in early May and couldn't find it. Shame on me for not reading the docs.

Robert Roskam

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