Getting a "Django can only handle ASGI/HTTP connections, not websocket." error when hosting ASGI on heroku?

Question

Been scrolling though every question on StackOverflow and Youtube to find an answer. I'm deploying both WSGI and ASGI/websockets via Django channels on Heroku. It works locally, but it's been giving me trouble during production.

Setup

Here's my procfile:

web: daphne API.asgi:application --port $PORT --bind 0.0.0.0 -v2
worker: python manage.py runworker background -v2

Settings.py:

# Redis Setup
ASGI_APPLICATION = 'API.routing.application'
CHANNEL_LAYERS = {
    "default": {
        "BACKEND": "channels_redis.core.RedisChannelLayer",
        "CONFIG": {
            "hosts": [(HEROKU_URL, 6379)],
        },
    },
}

asgi.py:

import os
import django
from django.core.asgi import get_asgi_application

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'API.settings')
django.setup()
application = get_asgi_application()

And finally, routing.py:

application = ProtocolTypeRouter({
    'websocket':AllowedHostsOriginValidator(
        AuthMiddlewareStack(
            URLRouter(
                [
                    url(r"^timer/$", TestConsumer.as_asgi()),
                ]
            )
        )
    )
    ,'channel':ChannelNameRouter({
        'background':BackgroundConsumer.as_asgi()
    })
})

Problem/logs

Heroku logs when connecting to the websocket:

2021-07-02T19:42:42.209398+00:00 app[web.1]: IP - - [02/Jul/2021:19:42:42] "GET /chat_switch/1/" 200 10480
2021-07-02T19:43:02.708851+00:00 app[web.1]: IP - - [02/Jul/2021:19:43:02] "WSCONNECTING /timer/" - -
2021-07-02T19:43:02.709658+00:00 app[web.1]: 2021-07-02 19:43:02,709 DEBUG    Upgraded connection [IP, 32183] to WebSocket
2021-07-02T19:43:03.058159+00:00 app[web.1]: 2021-07-02 19:43:03,057 ERROR    Exception inside application: Django can only handle ASGI/HTTP connections, not websocket.
2021-07-02T19:43:03.058167+00:00 app[web.1]: Traceback (most recent call last):
2021-07-02T19:43:03.058168+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/django/core/handlers/asgi.py", line 143, in __call__
2021-07-02T19:43:03.058168+00:00 app[web.1]:     raise ValueError(
2021-07-02T19:43:03.058169+00:00 app[web.1]: ValueError: Django can only handle ASGI/HTTP connections, not websocket.
2021-07-02T19:43:03.059813+00:00 app[web.1]: 2021-07-02 19:43:03,059 INFO     failing WebSocket opening handshake ('Internal server error')
2021-07-02T19:43:03.060494+00:00 app[web.1]: 2021-07-02 19:43:03,060 WARNING  dropping connection to peer tcp4:IP:32183 with abort=False: Internal server error
2021-07-02T19:43:03.064484+00:00 app[web.1]: 2021-07-02 19:43:03,063 DEBUG    WebSocket closed for [IP, 32183]

Other than that, the regular API functions work as intended.

What I've tried

Changed procfile to the answer from here: Websockets with Django Channels on Heroku (didn't work)
Changed asgi.py to the answer from here: Django daphne asgi: Django can only handle ASGI/HTTP connections, not websocket (no difference in ouput)
Tinkered with Redis URL in settings.py
Contemplating changing careers

If anyone knows what I can do from here, I'd appreciate it.

Konstantin K. · Accepted Answer · 2021-07-02 20:51:15Z

It doesn't look like application in routing.py is doing anything. I see it specified in ASGI_APPLICATION but, I believe, that's used by the development server (manage.py runserver). In your daphne command, you're serving API.asgi:application which only defines the django ASGI app - the "http" connection handler.

What you need is to replace get_asgi_application() with a ProtocolTypeRouter which defines how each protocol is served - "http" goes to the django ASGI application and "websocket" goes to your consumer routes.

Take a look at the Deploying section in Channels documentation. Your asgi.py could look something like this (I didn't include your consumer imports):

import os

from django.core.asgi import get_asgi_application
from django.urls import path

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'API.settings')

django_asgi_app = get_asgi_application()

from channels.auth import AuthMiddlewareStack
from channels.security.websocket import AllowedHostsOriginValidator
from channels.routing import ProtocolTypeRouter, URLRouter, ChannelNameRouter

application = ProtocolTypeRouter({
    'http': django_asgi_app,
    'websocket': AllowedHostsOriginValidator(
        AuthMiddlewareStack(
            URLRouter(
                [
                    path('timer/', TestConsumer.as_asgi()),
                ]
            )
        )
    ),
    'channel': ChannelNameRouter({
        'background': BackgroundConsumer.as_asgi()
    })
})

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