Unable to view rails app running in docker contain

Question

I am running a rails app in a docker container and after executing docker-compose up I look in the browser and see ERR_CONNECTION_REFUSED. I have tried port forwarding via docker run -p 3000:3000 docker_app and still nothing. Any ideas?

Answer 1

If you are using boot2docker or docker toolbox or docker machine (on an OS different from Linux, meaning using a VirtualBox VM), that means you need to forward that port at the VM level itself:

VBoxManage controlvm boot2docker-vm natpf1 "name,tcp,,3000,,3000"

The VM needs to forward that port from localhost to itself, before the docker port mapping can act.
I had a similar case with this answer.

Then try to access http://$(docker-machine ip default):3000, as mainframer comments.