low-end persistence strategies?

[pyguy2 at gmail.com]

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