How to read environment variable from Apache updating from Django 1.6.5 to 1.7 - django

Question

I want to read environment variables from Apache vhost config file and store them into Django settings.
Before updating to Django 1.7 everything was fine but now it is broken.
It seems the problem is in my wsgi.py script, when I call
_application = get_wsgi_application()
because it reads config file before the environment variable is set.
Is there another way to do this in Django 1.7?
In my /etc/apache2/sites-enabled/mysyte.conf I have:
<VirtualHost *:80>
...
SetEnv SECRET_KEY ...
SetEnv EMAIL_HOST ...
SetEnv EMAIL_HOST_PASSWORD ...
SetEnv EMAIL_HOST_USER ...
SetEnv EMAIL_PORT 25
...
In my wsgi.py:
import os
from os.path import abspath, dirname
from sys import path
SITE_ROOT = dirname(dirname(abspath(__file__)))
path.append(SITE_ROOT)
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "locacle.settings.production")
_application = get_wsgi_application()
def application(environ, start_response):
for key, value in environ.items():
if isinstance(environ[key], str):
os.environ[key] = environ[key]
return _application(environ, start_response)
In my settings.py I have:
from os import environ
from base import *
def get_env_setting(setting):
""" Get the environment setting or return exception """
try:
return environ[setting]
except KeyError:
error_msg = "Set the %s env variable" % setting
raise ImproperlyConfigured(error_msg)
EMAIL_HOST = get_env_setting('EMAIL_HOST')
...
This is what log file reports:
...
mod = importlib.import_module(self.SETTINGS_MODULE)
File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
__import__(name)
File "/home/www/.../settings/production.py", line 34, in <module>
EMAIL_HOST = get_env_setting('EMAIL_HOST')
File "/home/www/...settings/production.py", line 21, in get_env_setting
raise ImproperlyConfigured(error_msg)
ImproperlyConfigured: Set the EMAIL_HOST env variable
...

Answer 1

I'm afraid that what you are trying to do here is inherently fragile, only worked by lucky accident on previous versions of Django, and will not work with Django 1.7 or any future version of Django. (Update: it also would make you potentially vulnerable to the "shellshock" bash bug, whereas WSGI normally isn't.)
The basic problem is that that WSGI environ is only available on a per-request basis, but you are trying to set global configuration for your Django process based on it. This is inefficient and conceptually broken (why are you re-setting OS environment variables again and again every single time a request comes in? what if different requests have a different WSGI environ?), and it can only work at all if Django waits to configure itself until the first request arrives.
But the unpredictable timing and ordering of Django's startup sequence in previous versions caused problems. For instance, when using runserver in local development Django would eagerly configure itself, due to validation checks, but under a production environment it would only configure itself lazily (which you were relying on), meaning that sometimes imports would happen in a different order and circular imports would crop up in production that weren't reproducible under runserver.
Django 1.7 includes a revamped startup sequence in order to address these problems, make the startup sequence predictable and consistent between development and production, and allow users to explicitly register code to run at startup time (via AppConfig.ready()). A side effect of this is that settings are configured when your process starts up (specifically, with the call to django.setup() in get_wsgi_application()), not waiting until the first request comes in.
If you're only running one Django site on this server, I would simply move your configuration into normal environment variables rather than SetEnv in your Apache config, and avoid the whole problem.
If you're running multiple Django sites which require different config through a single Apache server, that won't work. In that case, perhaps someone more familiar with Apache and mod_wsgi can give you advice on how to pass environment variables from your Apache config to your Django process in a reliable way; I've personally found the process model (actually, process models, since there's more than one depending how you configure it) of mod_wsgi confusing and error-prone when trying to run multiple independently-configured sites through one server. I find it simpler to use a dedicated WSGI server like gunicorn or uwsgi and have Apache (or nginx) proxy to it. Then it's simple to run multiple gunicorn/uwsgi processes with separate OS environments.