Dokku: Listen to multiple ports from an app
This can be hacked together by using https://github.com/statianzo/dokku-shoreman or https://github.com/statianzo/dokku-supervisord, but you need to manually make sure that there are no port collisions on the dokku host.
When https://github.com/progrium/dokku/issues/732 is resolved, you will be able to deploy the second app as a worker that will listen on a port assigned by docker.