What is so bad with threadlocals

Question

Everybody in Django world seems to hate threadlocals(http://code.djangoproject.com/ticket/4280, http://code.djangoproject.com/wiki/CookBookThreadlocalsAndUser). I read Armin

Answer 1

I avoid this sort of usage of threadlocals, because it introduces an implicit non-local coupling. I frequently use models in all kinds of non-HTTP-oriented ways (local management commands, data import/export, etc). If I access some threadlocals data in models.py, now I have to find some way to ensure that it is always populated whenever I use my models, and this could get quite ugly.

In my opinion, more explicit code is cleaner and more maintainable. If a model method requires a subdomain in order to operate, that fact should be made obvious by having the method accept that subdomain as a parameter.

If I absolutely could find no way around storing request data in threadlocals, I would at least implement wrapper methods in a separate module that access threadlocals and call the model methods with the needed data. This way the models.py remains self-contained and models can be used without the threadlocals coupling.