I'm in the process of building a simple update server for an application. The parts of the application being updated are configuration files; the most up-to-date copies of these files exist on the update server and these files can be edited by the individual managing the application (the "application manager") at any time. However, I don't want the application to be able to download one of these files while the file is being edited by the application manager; this would obviously cause consistency issues. How can I prevent these files from being accessed in an inconsistent state? Alternatively, would a solution be to provide a checksum along with the file that the application could use to determine if the file was received in a consistent state?
EDIT: I've seen this post concerning access restrictions using .htcaccess and think it could be of use. However, I want the application manager to do as little thinking as possible; having them forget to re-allow connections might be problematic. That being said, they're going to have to do some work at some point; maybe this is the way I should go?