#33860: When debug level == DEBUG, loading admin page causes a voluminous
exception
message to be emitted in logging
-------------------------------------------+------------------------
Reporter: ultra-andy | Owner: (none)
Type: Bug | Status: new
Component: Error reporting | Version: 4.0
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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1. Follow the standard tutorials to create a basic Django app:
https://docs.djangoproject.com/en/4.0/intro/tutorial01/
https://docs.djangoproject.com/en/4.0/intro/tutorial02/
2. Paste in the following logging to settings.py:
{{{
#!python
import os
LOGGING = {
'version': 1,
'disable_existing_loggers': False,
'handlers': {
'console': {
'class': 'logging.StreamHandler',
},
},
'root': {
'handlers': ['console'],
'level': 'DEBUG',
},
'loggers': {
'django': {
'handlers': ['console'],
'level': os.getenv('DJANGO_LOG_LEVEL', 'DEBUG'),
'propagate': False,
},
},
}
}}}
3. Run the server: python manage.py runserver
4. Visit the admin page in your browser
(http://127.0.0.1:8000/admin/login/)
5. View the console output - two apparent exception traces will be
prominent. These are '''NOT''' unhandled exceptions, despite appearances!
The problematic logging message is generated in django/template/base.py,
at line 930 [class Variable, method _resolve_lookup()].
This logging message is generated when an exception is thrown in parsing
html templates, given the app context - if the app context does not
contain a 'subtitle' key (which is the case for a plain vanilla Django
test app as documented above), an exception gets thrown and then handled
internally, '''but''' a voluminous logger message is generated, which
occupies acres of terminal real estate and appears to contain two separate
exception stack traces. The debug level needs to be set to DEBUG for this
to occur.
For a stable framework like Django, logging messages from within Django
should be kept minimal and '''relevant to the framework user'''. This is
so that the framework user can add their own logging in creating their
service, and only encounter logging messages by Django itself which are
likely to be relevant to them as a user of the framework, given the
logging level they have specified.
This logging message breaks this principle. I'm developing my own service
using Django, and when this message cropped up in my logs it then caused
me to look for a bug in my own code, then I created a ticket on my own
project to investigate it, and I've now spent two days of professional
time investigating this voluminous log message before working out that
it's a Django bug. This isn't consistent with Django being 'a framework
for professionals with deadlines'!
The problematic commit that added this problematic logging was made in
2015, so this bug affects all current Django releases.
https://github.com/Selby-
Dynamics/django/commit/dc5b01ad05e50ccde688c73c2ed3334a956076b0
The logging code was modified (but not fundamentally changed) in this
commit:
https://github.com/Selby-
Dynamics/django/commit/85c52743f7b99ac6575d87080a9ffb7540acbf18
'''I propose that the fix is to remove all the code corresponding to the
2015 commit.'''
-------------------------------------------------------------------------------------------------------------------------------------------
Further work for someone with more experience of Django could be to do the
following:
1. Review all logging (do a "grep -rn 'logging.' .") and check that all
logging messages are relevant to framework users
2. Check use of 'subtitle' to see if subtitle is still used/required in
the framework
--
Ticket URL: <https://code.djangoproject.com/ticket/33860>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
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