Database query in custom authentication cause SynchronousOnlyOperation Error

In Custom Authentication section of documentation, there is database query in __call__ method:

def __call__(self, scope):
        ...
        user = User.objects.get(id=int(scope["query_string"]))
        ...

It’s OK with Django 2, but in Django 3 it cause django.core.exceptions.SynchronousOnlyOperation error. please update docs, and explain how to use database query in Custom Authentications. Thanks.

[AmirMahmood]

@jkupka You can use below code, Until docs be updated.

from channels.db import database_sync_to_async

@database_sync_to_async
def get_user(user_id):
    try:
        return User.objects.get(id=user_id)
    except User.DoesNotExist:
        return AnonymousUser()

class QueryAuthMiddleware:
    """
    Custom middleware (insecure) that takes user IDs from the query string.
    """

    def __init__(self, inner):
        # Store the ASGI application we were passed
        self.inner = inner

    def __call__(self, scope):
        return QueryAuthMiddlewareInstance(scope, self)


class QueryAuthMiddlewareInstance:
    def __init__(self, scope, middleware):
        self.middleware = middleware
        self.scope = dict(scope)
        self.inner = self.middleware.inner

    async def __call__(self, receive, send):
        self.scope['user'] = await get_user(int(self.scope["query_string"]))
        inner = self.inner(self.scope)
        return await inner(receive, send)

TokenAuthMiddlewareStack = lambda inner: TokenAuthMiddleware(AuthMiddlewareStack(inner))

[daxaxelrod]

Hey, thanks for the work done thus far! Adapted @AmirMahmood solution for django rest framework’s token auth based on the old impl. See below:

@database_sync_to_async
def get_user(token_key):
    try:
        return get_user_model().objects.get(auth_token__key=token_key)
    except get_user_model().DoesNotExist:
        return AnonymousUser()

class TokenAuthMiddlewareInstance:
    """
    Token authorization middleware for Django Channels 3
    """

    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:
            token_name, token_key = headers[b'authorization'].decode().split()
            if token_name == 'Token':
                self.scope['user'] = await get_user(token_key)
        inner = self.inner(self.scope)
        return await inner(receive, send)

class TokenAuthMiddleware:
    def __init__(self, inner):
        self.inner = inner

    def __call__(self, scope):
        return TokenAuthMiddlewareInstance(scope, self)


TokenAuthMiddlewareStack = lambda inner: TokenAuthMiddleware(AuthMiddlewareStack(inner))