Django 3.0 + Channels + ASGI + TokenAuthMiddleware - django

Question

I upgraded to Django 3.0 and now I get this error when using websockets + TokenAuthMiddleware:
SynchronousOnlyOperation
You cannot call this from an async context - use a thread or sync_to_async.

Answer 1

The problem is that you can't access synchronous code from an asynchronous context. Here is a TokenAuthMiddleware for Django 3.0:
# myproject.myapi.utils.py
from channels.auth import AuthMiddlewareStack
from channels.db import database_sync_to_async
from django.contrib.auth.models import AnonymousUser
from rest_framework.authtoken.models import Token
#database_sync_to_async
def get_user(headers):
try:
token_name, token_key = headers[b'authorization'].decode().split()
if token_name == 'Token':
token = Token.objects.get(key=token_key)
return token.user
except Token.DoesNotExist:
return AnonymousUser()
class TokenAuthMiddleware:
def __init__(self, inner):
self.inner = inner
def __call__(self, scope):
return TokenAuthMiddlewareInstance(scope, self)
class TokenAuthMiddlewareInstance:
"""
Yeah, this is black magic:
https://github.com/django/channels/issues/1399
"""
def __init__(self, scope, middleware):
self.middleware = middleware
self.scope = dict(scope)
self.inner = self.middleware.inner
async def __call__(self, receive, send):
headers = dict(self.scope['headers'])
if b'authorization' in headers:
self.scope['user'] = await get_user(headers)
inner = self.inner(self.scope)
return await inner(receive, send)
TokenAuthMiddlewareStack = lambda inner: TokenAuthMiddleware(AuthMiddlewareStack(inner))
Use it like this:
# myproject/routing.py
from myapi.utils import TokenAuthMiddlewareStack
from myapi.websockets import WSAPIConsumer
application = ProtocolTypeRouter({
"websocket": TokenAuthMiddlewareStack(
URLRouter([
path("api/v1/ws", WSAPIConsumer),
]),
),
})
application = SentryAsgiMiddleware(application)

Answer 2

As #tapion stated this solution doesn't work anymore since channels 3.x
Newer solution can be a little bit tweaked:
class TokenAuthMiddleware:
def __init__(self, inner):
self.inner = inner
async def __call__(self, scope, receive, send):
headers = dict(scope['headers'])
if b'authorization' in headers:
scope['user'] = await get_user(headers)
return await self.inner(scope, receive, send)