Selenium Grid in Docker compose file with WebDriver for Firefox and Chrome

docker-compose.yml

version: '2'

services:

  seleniumhub:
    container_name: seleniumhub
    image: selenium/hub
    ports:
     - "4444:4444"

  firefoxnode:
    container_name: firefoxnode
    image: selenium/node-firefox-debug
    ports:
     - 4577
    links:
     - seleniumhub
    environment:
      - HUB_PORT_4444_TCP_ADDR=seleniumhub
      - HUB_PORT_4444_TCP_PORT=4444
    extra_hosts:
      - "app.mywebapp.com:172.20.129.2"
    volumes:
      - /dev/shm:/dev/shm

  chromenode:
    container_name: chromenode
    image: selenium/node-chrome-debug
    ports:
      - 4578
    links:
      - seleniumhub
    environment:
      - HUB_PORT_4444_TCP_ADDR=seleniumhub
      - HUB_PORT_4444_TCP_PORT=4444
    extra_hosts:
      - "app.mywebapp.com:172.20.129.2"
    volumes:
      - /dev/shm:/dev/shm

networks:
  default:
    external:
      name: build_static-network

# -hub URL http://$HUB_PORT_4444_TCP_ADDR:$HUB_PORT_4444_TCP_PORT/grid/register