In talks about how to do throttled rollouts for Go Faster we came up with the idea of having a "fallback" mapping - a release that would be returned if a user is on the wrong side of a background rate dice roll. This would let us do things such as roll out an updated version of Hello at a low rate, while still returning the latest released version to everyone else (in case they aren't up to date already). This would probably be useful for Firefox when we're doing throttled rollouts as well.
Ninad has been working on this in https://github.com/mozilla/balrog/pull/160.
Commit pushed to master at https://github.com/mozilla/balrog https://github.com/mozilla/balrog/commit/2b4eab7acccc089419ed0ec87c92089e5798dea6 Bug 1282891: support fallback mappings when background rate roll fails (#160). r=bhearsum
This is in production, thanks Ninad!