Django: How to handle exception when the database is down/cannot connect?

Question

We're having a problem on our django application. Occasionally, the database goes down/has too many connections, etc and Django continuously raises exceptions.

How can we catch these exceptions and redirect the user to an error page?

Answer 1

If you want to show custom page for error 500 and then save the exceptions in logs, the following steps may help:

1. To view exceptions you can use logging setup from here.
2. Create a new HTML file error_500.html in your app templates/errors/ folder.

3. Add view function error_500 to your app's views.py:

   def error_500(request): return render(request, 'errors/error_500.html')

4. Add routing to urls.py (either main or in your app's). For example

   from django.conf.urls import handler404, handler500 from YOURAPP import views as yourapp_views

   handler404 = yourapp_views.error_404 handler500 = yourapp_views.error_500

From now, in production mode (DEBUG=0, ALLOWED_HOSTS is set, run as WSGI etc.) , when exception occurs, Django should display contents of your error_500.html as Error 500 page. You will see more information in system logs.

Answer 2

With DatabaseError in test view below, you will be able to handle all database exceptions then redirect users to error page when a database exception occurs:

# "views.py"

from django.db import transaction, DatabaseError 
from django.shortcuts import redirect, render
from .models import Person

@transaction.atomic
def test(request):
    try:
        obj = Person.objects.get(id=2)
        obj.name = "David"
        obj.save()
    except DatabaseError as e:
        return redirect("/error-page/")

    return render(request, 'myapp/success.html')

*In Django documentation, you can check database exceptions and in PEP 249, you can check what causes the database exceptions. For example, OperationalError is caused by unexpected disconnection, statement timeout, lost update and write skew conditions and so on.