Google App Engine with local Django 1.1 gets Intermittent Failures

I'm using the Windows Launcher development environment for Google App Engine.

I have downloaded Django 1.1.2 source, and un-tarrred the "django" subdirectory to live within my application directory (a peer of app.yaml)

At the top of each .py source file, I do this:

import settings
import os
os.environ["DJANGO_SETTINGS_MODULE"] = 'settings'

In my file settings.py (which lives at the root of the app directory, as well), I do this:

DEBUG = True
TEMPLATE_DIRS = ('html')
INSTALLED_APPS = ('filters')

import os
os.environ["DJANGO_SETTINGS_MODULE"] = 'settings'
from google.appengine.dist import use_library
use_library('django', '1.1')
from django.template import loader

Yes, this looks a bit like overkill, doesn'开发者_开发问答t it?

I only use django.template. I don't explicitly use any other part of django.

However, intermittently I get one of two errors:

1) Django complains that DJANGO_SETTINGS_MODULE is not defined.

2) Django complains that common.html (a template I'm extending in other templates) doesn't exist.

95% of the time, these errors are not encountered, and they randomly just start happening. Once in that state, the local server seems "wedged" and re-booting it generally fixes it.

What's causing this to happen, and what can I do about it? How can I even debug it?

Here is the traceback from the error:

Traceback (most recent call last):
  File "C:\code\kwbudget\edit_budget.py", line 34, in get
    self.response.out.write(t.render(template.Context(values)))
  File "C:\code\kwbudget\django\template\__init__.py", line 165, in render
    return self.nodelist.render(context)
  File "C:\code\kwbudget\django\template\__init__.py", line 784, in render
    bits.append(self.render_node(node, context))
  File "C:\code\kwbudget\django\template\__init__.py", line 797, in render_node
    return node.render(context)
  File "C:\code\kwbudget\django\template\loader_tags.py", line 71, in render
    compiled_parent = self.get_parent(context)
  File "C:\code\kwbudget\django\template\loader_tags.py", line 66, in get_parent
    raise TemplateSyntaxError, "Template %r cannot be extended, because it doesn't exist" % parent
TemplateSyntaxError: Template u'common.html' cannot be extended, because it doesn't exist

And edit_budget.py starts with exactly the lines that I included up top.

All templates live in a directory named "html" in my root directory, and "html/common.html" exists. I know the template engine finds them, because I start out with "html/edit_budget.html" which extends common.html.

It looks as if the settings module somehow isn't applied (because that's what adds html to the search path for templates).

Firstly, although django is now a LOT more compatible with app engine than it once, some major incompatibilities still exist between the two platforms, meaning that you can't just dump a stock copy of django into your appengine directory and have it work out of the box. Things will error in strange ways.

There are a number of projects which aim to improve compatibility between the two projects, the most prominent is app-engine-patch. I highly suggest reading the following article http://code.google.com/appengine/articles/app-engine-patch.html and the rest of the articles located at code.google.com/appengine/articles/ under the django tab.

as for some of you're specific problems, you could try this within your setup script:

#setup django environment
from django.core.management import setup_environ
import settings
setup_envion(settings)

this is what django uses internally for setting up the environment within manage.py and is the accepted best practice for setting up django for use with scripts (like app engine).

I'm having exactly the same issue, and I haven't been able to work around it... though I've noticed it happens a LOT less with the real GAE than it does with the development server I run on my Linux workstation.