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
23023	Update warning about local-memory cache for sessions	django@…	Tim Graham	"I am suggesting an addition of a sentence to the warning about using the local-memory cache for caching sessions due to a tricky to replicate problem that I stumbled on. I started using cached_db ages ago but didn't configure the cache settings, leaving it as the default local-memory cache (In 1.2 it says that ""This cache is multi-process and thread-safe"", but that's not the case now. Oh wait, in 1.2, the next paragraph contradicts it's multi-process safeness - that's fixed now).

Mostly I'd sometimes notice that messages didn't appear until one or two pages after it should, but recently, I actually started using the session for more stuff and stuff was breaking sometimes and other times not - session looked good in the database, but my views weren't always seeing the same values. And everything was fine with runserver...

Doh! Multiple processes in WSGI/Apache2...

https://docs.djangoproject.com/en/dev/topics/http/sessions/#using-cached-sessions
So, just because the local-memory cache is the default if not otherwise configured, add an extra line to the existing warning:

Additionally, the local-memory cache backend is NOT multi-process safe, therefore probably not a good choice for production environments.
"	Cleanup/optimization	closed	Documentation	dev	Normal	fixed			Ready for checkin	1	0	0	0	1	0