You do not need to use a 24/7 process for low end persistance, if you rely on the fact that only one thing can ever succeed in making a directory. If haven't seen a filesystem where this isn't the case. This type of locking works cross-thread/process whatever.
An example of that type of locking can be found at: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/252495 The only problem with this locking is if a process dies w/out cleaning up the lock, how do you know when to remove them? If you have the assumption that the write to the database is quick (ok for low end), just have the locks time out after a minute. And if you need to keep the lock longer, unpeel appropriately and reassert them. With 2 lock directories, 2 files and 1 temporary file, you end up with a hard to break system. The cost is disk space, which for low end should be fine. Basically, the interesting question is, how far can one, cross-platform, actually go in building a persistence system with long term process business. john -- http://mail.python.org/mailman/listinfo/python-list
