We're moving our website to new Cloud Load Balanced servers on Rackspace. It's all a bit of a new experience for us, we've ironed out most of the issues, apart from one.
We've set up the new servers to lsync from Server A to Server B (Server A is master).
From time to time we see css/js files 404. We can guess what's wrong, it's file syncing not happening fast enough between servers, and when a cache clear occurs on Server A, such as a cron run, then Server B is requesting the old CSS/JS files, and that request may go to Server A.
What is the proper way to set up Drupal 7 on load balanced servers so that CSS and JS files are in sync and don't cause 404?