Creating a user and immediately authenticating fails on deployed app-engine

Question

I've got a simple registration view that takes the user's credentials, creates the user and immediately signs them in. This works perfectly fine on my local development server but when deployed the call to authenticate seems to return None. Annoyingly it doesn't seem to happen every time. Here's my view code:

def register_view( request ):
    import django.contrib.auth as auth
    if request.method == 'POST':
        form = auth.forms.UserCreationForm( request.POST )
        if form.is_valid():
            username = request.POST.get( 'username', None )
            password1 = request.POST.get( 'password1', None )
            auth.models.User.objects.create_user( username=username, password=password1 )
            user = auth.authenticate( username=username, password=password1 )
            if user != None:
                auth.login(request, user)
                return HttpResponseRedirect( request.REQUEST.get( 'next', '/' ) )
            else:
                login_form = auth.forms.AuthenticationForm( data= { 'username': username, 'password': password1 } )
                return render(request, 'login.html', { 'form': login_form } )
        else:
            return render(request, 'register.html', { 'form': form })
    else:
        form = auth.forms.UserCreationForm( error_class=BlogErrorList )
        return render(request, 'register.html', { 'form': form } )

I found this other question that I believe it's the same problem but there was never a verified answer.

I have the same feeling it's a database problem, I am using a High Replication datastore and added 'HIGH_REPLICATION': True to my database settings as decribed here, but that didn't make a difference.

Any ideas what could cause this?

-- EDIT --

I'm using Django-nonrel 1.4 and the standard django.contrib.auth system. The User model is created here and the authentication backend authenticates the user here.

Answer 1

You haven't shown how you the user is defined, and how your auth code is finding the user.

If you are not getting the use by key, or an ancestor query then you will be running into eventual consistency.

You should read this https://developers.google.com/appengine/docs/python/datastore/structuring_for_strong_consistency