id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
7062	Multiple projects with different TIME_ZONE settings under mod_python can cause unexpected date/time behaviour	durdinator	nobody	"When running Django under mod_python, if there are multiple projects running with different `TIME_ZONE` settings, this can under some circumstances lead to the time zone (and hence the value returned by `datetime.datetime.now()`) being different for subsequent requests to the same URL.

We encountered this problem running Apache 2.0 with the prefork MPM, with 10 subprocesses. While most of the numerous Django projects on the server had `TIME_ZONE = 'Europe/London'` in the settings module, two had inadvertently been left with `TIME_ZONE = 'America/Chicago'`.  After investigating a problem where a time-based query would return unexpectedly different results for repeated requests, we found that `datetime.datetime.now()` was mostly returning the local time value (10.05 am), but occasionally returning the wrong time (4.05 am).  This 6 hour difference, not coincidentally, is the current difference between the America/Chicago and Europe/London time zones.  Another instance of this problem was described in http://groups.google.com/group/django-users/browse_thread/thread/b2f8722f58b270fd/

Since the environment is maintained for each Apache subprocess, modifying it via `os.environ` in one subinterpreter causes the modified environment to be visible in other subinterpreters, which may be serving a different site.  This causes a problem at present, as `os.environ['TZ']` is set only once per project, when the settings are first loaded: http://code.djangoproject.com/browser/django/trunk/django/conf/__init__.py#L116

If the `TZ` environment variable were set per request (as is done with DJANGO_SETTINGS_MODULE and other environment variables passed through from the apache config via `SetEnv` commands), then the correct time zone setting would be available for each project.  I have attached a patch against SVN HEAD to do this in the mod_python handler.


Until this is corrected, a workaround is:

  * Ensure that all django projects running under mod_python are using the same TIME_ZONE setting
  * Or if different time zones are required, then ensure that the apache config uses SetEnv to set the correct TZ variable for every project.

"	Bug	closed	Core (Other)	dev	Normal	invalid	mod_python time timezone	me@… nreilly@…	Accepted	1	0	0	1	0	0