WSGI post-process cleanup

Question

I'm running a TurboGears app with mod_wsgi and apache, using pymongo wrapped with Ming for persistence. To failproof and scale my app I was interested in using mongo's support for replica sets through a pymongo ReplicaSetConnection.

However, as specified in the above links, one must call close() when done with every pymongo ReplicaSetConnection object, otherwise it will leave a bunch of zombie processes floating around (wtf pymongo). This sort of behavior isn't supported very well in Ming (it actually doesn't really support Replica Sets yet), but I managed to write a cleanup function that closes all pymongo connections.

Now I want to run my cleanup function on process cleanup for all my app processes. These have two basic entry points: mod_wsgi through apache and paster commands. It is no problem to add my cleanup to the paster commands, but is there a way to specify a cleanup function for wsgi processes?

If not, any other advice for setting this up correctly?

Answer 1

You have no guarantee your code will even be called as processes can just crash or be forcibly exited before it is called. With that caveat, read the mod_wsgi documentation about this specific issue:

http://code.google.com/p/modwsgi/wiki/RegisteringCleanupCode

Answer 2

TurboGears itself also provides the shutdown hook which can be registered using base_config.register_hook inside config/app_cfg.py.

The shutdown hook gets called whenever the process exists