Domain resolves on host machine but not inside docker container

Question

I have two containers, one running a Node.js process that launches protractor, and another running a standalone Selenium container. The file looks like this:

version: '2'

services:
  www.example.localhost:
    build: .
    depends_on:
      - selenium
    dns_search:
      - static.example.localhost
    extra_hosts:
      - "static.example.localhost:127.0.0.1"
    ports:
      - "3000:3000"
      - "4000:4000"
    volumes:
      - ./src:/code/src
      - ./api:/code/api
    entrypoint: "npm run"
    command: "test:e2e"

  selenium:
    dns_search:
      - selenium.example.localhost
    image: selenium/standalone-chrome-debug:2.52.0
    environment:
      no_proxy: localhost
    volumes:
      - /dev/urandom:/dev/random
    ports:
      - "4444:4444"
      - "6900:5900"

www.example.localhost runs protractor, which in turn connects to the selenium container with these lines in protractor.config.js:

seleniumAddress: "http://selenium:4444/wd/hub",
directConnect: false,

When I run VNC on the selenium container, open up the chrome browser inside the container and type www.example.localhost:3000 it fails to resolve the domain. However when I run wget www.example.localhost:3000 it gets the index.html file just fine. Any idea what I'm doing wrong?

Answer 1

Turns out in Google Chrome, any domain ending in localhost resolves to 127.0.0.1, no matter what DNS settings you have. Changing the domain from .localhost to .dev fixes it.