I have a Django app, which spawns a thread to communicate with another server, using Pyro.
Unfortunately, it seems like under fastcgi, multiple versions of this thread are fired off, and a dictionary that should be globally constant within my program, isn't. (Sometimes it has the values I expect, sometimes not)
What's the best way to ensure that there's one and only one copy of a dictionary in a django / fastcgi app?
I strongly recommend against relying on global anything in django. The problem is that, just as you seem to be encountering, the type of deployment will determine how (or whether or not) this global state is shared. To be a style nazi, that's a completely different level of abstraction from the code, which is relying on some guarantee of consistent global state.
I'm not experienced with fastcgi, but my understanding is that it, like many other frameworks, has a pre-forked and a threaded mode. In pre-forked mode, you have separate processes, not threads, running your python code. This spells nightmare for shared global state.
Barring some fragile workaround, which ought to be possible and which someone may or may not suggest, the only persistence you can really rely on is in the database, and, to a lesser extent, whatever caching mechanism you choose. You could use the low-level api to cache and retrieve keys and values.