Debugging Django in Production

May 17, 2017

Django's debugger works great in a development environment, but one of the first rules of deployment is to set DEBUG = false: after all, you wouldn't want every friendly visitor to see a full stack trace any time something goes wrong. This can make debugging tricky, however, when an error occurs on your production site that isn't easily replicable in the development server.

The code below will allow superusers to see a full stack trace on your production server, while other users receive your lovely 500 error page. This is adapted for Django >=1.10 from an extremely helpful article by Eric Holscher (which itself expanded on this snippet). Given the updates to middleware configuration beginning in 1.10, a few changes are needed for the fresher versions of Django.

To implement this magic, create a middleware folder in one of your application directories (I use the same directory housing my project's main settings.py file). Add a debug.py file containing the following code:

# my_project/my_app/middleware/debug.py
from django.views.debug import technical_500_response
import sys

class UserBasedExceptionMiddleware(object):
    def __init__(self, get_response):
        self.get_response = get_response

    def process_exception(self, request, exception):
        # Return debuggable stack trace only if the current user is logged in as a superuser
        if request.user.is_superuser:
            return technical_500_response(request, *sys.exc_info())

    def __call__(self, request):
        response = self.get_response(request)
        return response

Defining process_exception allows you to intercept any exceptions that occur. Here we check to see if the current user is a super one -- if so, give them a full readout. Otherwise, process_exception doesn't return anything, letting Django's default exception handling kick in.

Next, add the path to your settings.py MIDDLEWARE definition:

MIDDLEWARE = [
    # .... Standard middleware here ....
    'my_app.middleware.debug.UserBasedExceptionMiddleware',
]

Very nice!

Know of another way to implement this? Shoot me a message and I'd love to hear about it.