A simple application that can be used together with https://hub.docker.com/r/jwilder/nginx-proxy.
Each docker's container which should be available through nginx-proxy have to have defined the environment variable VIRTUAL_HOST - container-url-lister scans environment variables set in containers (through the docker api) and displays in form of the url list all VIRTUAL_HOST variables found.
The built image can be found at: https://hub.docker.com/repository/docker/lbacik/containers-url-lister