In my explorations, I’m actually doing it with machines, so the good news is that it should work with fly processes. In fact, the sed commands I included above turns off bind and protected mode to enable this and aren’t necessary in a single VM deployment.
To get that to work, obviously drop the install of ruby-foreman, don’t make changes to fly.rake and don’t add a Procfile.fly.
I said that that was the good news. The one part that I haven’t worked out yet is the service discovery. In short, the remaining issue is what you set the REDIS_URL to for such a configuration. The above assumes that you want to run redis on a port that is not exposed to the internet, and makes use of Private Networking · Fly Docs only.
For now, I get around this by creating a small rake task that I invoke via rails deploy instead of fly deploy but I’m continuing to look for a better way. If you want to see this in action, I have a demo that you can run: Progress update on scaling a Rails Application - #2 by rubys