Django signals on GAE with django-nonrel

Question

I am using django-nonrel for my project on GAE. My requirement is that in my application at a time only one user should login with the given username. I tried to implement the following suggested approaches: Allow only one concurrent login per user in django app and How can I detect multiple logins into a Django web application from different locations? But the problem is that both of the approaches working on the development server but didn't work on google app engine. So I switched to django-signals as my alternate approach. I created one post_login signal which will store the username for every login user in a table Visitor in database. On every logout,other signal post_logout will remove the user from this table.The part of codes are as:

#signals.py
post_login = django.dispatch.Signal(providing_args=['request', 'user'])
post_logout = django.dispatch.Signal(providing_args=['request', 'user'])
#models.py
def login_handler(sender,user, **kwargs):
    try:
        result=Visitor.objects.get(user=user)
        print "You already have login with your name"
    except:
        visitor=Visitor()
        visitor.user=user
        visitor.save()
post_login.connect(login_handler)


def logout_handler(sender,user, **kwargs):
    try:
        result=Visitor.objects.get(user=user)
        result.delete()
    except:
        return False
post_logout.connect(logout_handler)

#django.contrib.auth.__init.py__
def login(request):
 :
 user_logged_in.send(sender=user.__class__, request=request, user=user)
  post_login.send(sender=None,request=request, user=user)

def logout(request):
:
user_logged_out.send(sender=user.__class__, request=request, user=user)
post_logout.send(sender=None,request=request, user=user)

Please note that I am getting the following error while running my application on google app engine. Error: Server Error The server encountered an error and could not complete your request.

Also I am not able to login into Admin part of the application. Please help me to find right approach to implement this requirement or let me know where I am doing wrong. Thanks for your patience for reading this huge problem description :-)

Answer 1

1.

You should not be editing the django framework like you are doing. Don't touch the files inside django.contrib.auth

If you wish to send a signal after someone is logged in, then send the signal in your view where you log the person in

2.

Not sure what your actual error is because you are not displaying it (if this is a dev environment set DEBUG = True to get a better stack trace) But by lookingat you code, you are not grabbing the arguments correctly in the signal handler. It should look more like this:

def login_handler(sender, **kwargs):
    try:
        user = kwargs['user']
        request = kwargs['request']
        result=Visitor.objects.get(user=user)
        print "You already have login with your name"
    except:
        visitor=Visitor()
        visitor.user=user
        visitor.save()
post_login.connect(login_handler)