Here are the steps I took to deploying my Rails 4.1/Jubilee app to heroku
Like the heroku directions for switching to JRuby, you want to specify JRuby as the engine as well as your desired version of JRuby. You'll also want to include the jubilee gem
ruby '2.0.0', engine: 'jruby', engine_version: '1.7.13' gem 'jubilee', :platforms => [:jruby]
Set Jubilee as your web serverYou want something like the below. The example is using the eventbus.
web: jubilee --eventbus /eventbus -e $RACK_ENV -p $PORT
Add the rails_12factor gem
Per the instructions at here you'll want to include this gem to serve up static assets and logging.
If you don't include this gem, heroku will complain, but go ahead and deploy. Said app won't have any assets served up, so you'll definitely want to include it
Set JRUBY_OPTSIf you need to set custom JRUBY_OPTS into heroku, you'll do it the way you would any other environment variable on heroku, for example:
heroku config:add JRUBY_OPTS="-J-Xmn128m -J-Xms768m -J-Xmx768m"
And that's all it took. Deploy and enjoy your Jubilee on heroku!