current workaround for async auth backend

Using Django Async/Channels
1

I’ve seen in django code base that BaseBackend already has aauthenticate and aget_user methods, but right now for the latest django 5.1.4 they are not available. What should I do if I need to load users from external sources asynchronously? I can’t just slam one of the methods of custom auth backend asgiref.async_to_sync coz it will throw “You cannot use AsyncToSync in the same thread as an async event loop - just await the async function directly.” Of course I can write a sync call to that external source, but it doesn’t look good…

2

in the end alongside custom async auth backend as a workaround I wrote simplified versions (hardcoded for backend) of aget_user, aauthenticate, custom AuthenticationMiddleware (that uses new aget_user), and then fixed reference to new aauthenticate inside login view.

everything works smoothly, but i’m not really happy with extra 50 lines of code, tho…

3

Let me see if I’ve got a good picture of what you’re doing:

  1. You’re in an async view or middleware.
  2. You’re calling into authenticate or get_user, which calls into the synchronous backend.
  3. Inside the backend, you’re needing to make an async call.

If that’s seems right, I think this error is appropriate, but it’s not quite helping you to see where it got messed up. You need the authenticate or get_user call to be sync_to_async, so that it won’t stall the async loop. It does that by starting that synchronous function in a different thread (that doesn’t have an event loop already), which will make it so that async_to_sync can do what you expect it to do.

So, for example to call authenticate from an async view you might be able to do:

async def my_view(request):
    await sync_to_async(authenticate)(...)
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4

I agree with Ryan, but just to add context the async backends will be released with Django 5.2

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