ruby on rails - Dockerized selenium browser cannot access Capybara test url -

i trying run ruby on rails feature tests on dockerized selenium standalone firefox browser. seems having issues networking because selenium instance can't connect url started capybara.

here's sample docker-compose.yml file:

ff:   image: selenium/standalone-firefox:2.48.2   container_name: firefox-browser web:   build: .   container_name: my-app   volumes:     - ".:/home/ubuntu/my-app"   command: /bin/bash -l scripts/docker-start-tests.sh   ports:     - "3000:3000" 

and start docker-compose networking enabled:

docker-compose --x-networking 

the test script runs rspec command this

rspec ./spec/features/login_spec.rb:43 

for docker tests have enabled remote driver capybara:

capybara.register_driver :docker_firefox |app|   capybara::selenium::driver.new(app, {     browser: :remote,     url: "#{env['ff_url']}/wd/hub",     desired_capabilities: selenium::webdriver::remote::capabilities.firefox   }) end 

and call test this:

unless env['ff_url'].nil?   capybara.current_driver = :docker_firefox   capybara.javascript_driver = :docker_firefox    capybara.app_host = "http://my-app:56555"   capybara.server_port = "56555"   # capybara.server_host = "my-app" end  visit root_path save_and_open_screenshot click_link "sign in" ... 

i can tail browser container logs , see selenium receives commands capybara. problem cannot connect url provided, can confirm screenshot.

firefox can't establish connection server @ my-app:56555

to better understand problem, started rails app , tried access selenium container. notice can access app selenium container if start rails app ip binding.

rails s puma -b 0.0.0.0 

this looks networking problem, can't figure out solution.

how can make selenium container access rails app running rspec feature tests capybara?

capybara (2.6.0) selenium-webdriver (2.48.1) 

thanks help.

the server thread rails runs test app in binds capybara.server_host interface (127.0.0.1 default) - can change whatever ip interface docker container can talk machine on - in case possibly

capybara.server_host = '0.0.0.0' # bind interfaces