On Tue, 2004-11-30 at 14:24 -0500, Neal D. Becker wrote: > Sean Middleditch wrote: > > [...] > > So far as implementation, this really is easy even with a (single) file- > > based backend. Robustness might take some work, but the basics are > > easy. You simply keep a list of all they keys that have been set, and > > when the Commit command comes along, lock the file(s) in question and > > modify them. On Rollback, just "forget" all the key changes that > > haven't been committed yet. Basically the hard part for the simple file > > backend is getting the commit to stay atomic on errors when you use > > multiple files. If you have multiple files being changed, I don't > > believe it's actually possible to be 100% atomic - you can reduce the > > chances of something breaking, but there will always be various race > > conditions in regards to when errors occur that could leave you in a > > half-committed state. > > > > rename is atomic. You can always use this fact if you need to. Yes. That doesn't help with the problem of making atomic commits to *multiple* files. You would have to perform multiple renames, of which some may succeed and others may fail for any of a number of reasons, and then you can't necessarily undo the ones you already did. Unless there is a way to do an atomic rename of multiple files, my point definitely still stands - multiple files cannot be modified atomically. > -- Sean Middleditch <elanthis@xxxxxxxxxxxxxxx> AwesomePlay Productions, Inc.
