[PYTHON] Django Server Error (500) Strategy [2019 Adcare]

This is my first participation in the Advent calendar. I look forward to working with you.

Overview

My hobby is Pythonista. I got started with Django this year and created a website. This time, I'm going to write a rough strategy for Django beginners who are the same as me, about the things that will first bother me and make a heartbreaking scream. It is ** Server Error (500) **.

At this time, try to display the error content on the screen, output the log, or notify Slack of the error content even temporarily.

Server Error (500) occurred

I'm a beginner, so I just added a bug to the views.py method.

views.py

def index(request):

    aaaa  #← Sudden aaaa

    return HttpResponse('<p>Hello world.</p>')

If DEBUG in settings.py is True, you will get a clear error message like this:

However, as soon as you change DEBUG to False, you will see a Server Error (500) from the parent's face.

This screen is displayed by handler500

The handler when a server error occurs is [django.conf.urls. \ _ \ _ Init \ _ \ _. Py](https://github.com/django/django/blob/master/django/conf/urls/ It was in init.py # L9).

django/conf/urls/__init__.py

handler500 = defaults.server_error

This handler500 is executed when an error occurs on the server. That is, the defaults.server_error function is executed. If you look inside django.views.defaults.server_error, you can see the process displaying this screen. It is described.

django/views/defaults.py

@requires_csrf_token
def server_error(request, template_name=ERROR_500_TEMPLATE_NAME):
    """
    500 error handler.
    Templates: :template:`500.html`
    Context: None
    """

    #Omission

        return HttpResponseServerError(
            ERROR_PAGE_TEMPLATE % {'title': 'Server Error (500)', 'details': ''},
            content_type='text/html',
        )

Then, the function to be assigned to handler500 should be a different function instead of defaults.server_error.

Assign a different function to handler500

1. Define your own server_error function
2. Assign it to handler500

Try defining your own server_error in views.py. Because the original one is defined in django.views.defaults.

views.py

@requires_csrf_token
def my_customized_server_error(request, template_name='500.html'):
    return HttpResponseServerError('<h1>Server Error (500)That's right</h1>')

The assignment to handler500 is done in urls.py. The original handler500 definition is in django.conf.urls.

urls.py

handler500 = views.my_customized_server_error

I was able to change the Server Error screen.

After that, you can write whatever you like in my_customized_server_error.

Example of my_customized_server_error

This is the code that normally prints.

views.py

@requires_csrf_token
def my_customized_server_error(request, template_name='500.html'):
    import traceback
    print(traceback.format_exc())
    return HttpResponseServerError('<h1>Server Error (500)That's right</h1>')

This code gives the same error screen as when DEBUG = True. This is easy to see, isn't it? (Small feeling)

views.py

@requires_csrf_token
def my_customized_server_error(request, template_name='500.html'):
    import sys
    from django.views import debug
    error_html = debug.technical_500_response(request, *sys.exc_info()).content
    return HttpResponseServerError(error_html)

Code that brings up the default Server Error (500) screen as seen from the parent's face. You can use the django.views.defaults.server_error you found earlier and you're good to go.

views.py

@requires_csrf_token
def my_customized_server_error(request, template_name='500.html'):
    from django.views.defaults import server_error
    return server_error(request, template_name)

Code that skips notifications to everyone's favorite Slack.

views.py

@requires_csrf_token
def my_customized_server_error(request, template_name='500.html'):
    import requests
    import json
    import traceback
    requests.post(
        'Your Slack Webhook URL',
        data=json.dumps({
            'text': '\n'.join([
                f'Request uri: {request.build_absolute_uri()}',
                traceback.format_exc(),
            ]),
            'username': 'Django error notification',
            'icon_emoji': ':jack_o_lantern:',
        })
    )
    return HttpResponseServerError('<h1>Server Error (500)That's right</h1>')

I flew. Since the directory structure of my place is displayed, I will put a mosaic.

Tomorrow's Django Advent Calendar is @boxboxbax. Good luck!