Set Up a Local Docker Selenium Hub

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1 Introduction

This how-to shows you an example of a simple setup of a Docker Selenium hub with a Chrome and a Firefox node on a Linux machine. The Docker works on a Windows machine as well, but the commands and configuration could be different. For the official project go to: https://github.com/SeleniumHQ/docker-selenium

2 Prerequisites

The following components are needed:

  • Some basic docker and docker-compose knowledge
  • A machine with the latest versions of docker and docker-compose installed
  • Your machine should allow connections from ATS on port 4444
  • Since version 2.6, ATS uses the Selenium 3.8.1 API. That’s why we recommend using this version of Selenium for the docker images as well

3 Installing Your Hub & Nodes with Docker-Compose

The following steps describe how to install your hub and nodes with Docker-Compose:

  1. Create a folder or directory to place your docker-compose file
  2. Create a docker-compose.yml in your folder/directory:

    hub: 
     image: selenium/hub:3.8.1
     environment:
        - TZ=Europe/Amsterdam
        - GRID_TIMEOUT=90
     ports:
        - 4444:4444
        
    firefox:
     image: selenium/node-firefox:3.8.1
     links:
        - hub:hub
     environment:
        - TZ=Europe/Amsterdam
        - SCREEN_WIDTH=1600
        - SCREEN_HEIGHT=900
        
    chrome:
     image: selenium/node-chrome:3.8.1
     links:
        - hub:hub
    environment:
        - TZ=Europe/Amsterdam
        - SCREEN_WIDTH=1600
        - SCREEN_HEIGHT=900
    volumes:
        - /dev/shm:/dev/shm
    privileged: true
    
  3. Open a console and give the following command from the folder/directory where you placed your docker-compose.yml:

    sudo docker-compose up -d
    

    The first time it will start pulling the images from the Docker hub.

  4. After the process has started, you can check the status with the following commands:

    sudo docker-compose ps
    
         Name                 Command           State           Ports         
    ---------------------------------------------------------------------
    docker_chrome_1    /opt/bin/entry_point.sh   Up                            
    docker_firefox_1   /opt/bin/entry_point.sh   Up                            
    docker_hub_1       /opt/bin/entry_point.sh   Up      0.0.0.0:4444->4444/tcp
    
  5. Check with the following link if the hub works: http://localhost:4444/grid/console. Note: You can also replace localhost with the server name or IP-address of the Docker host.

    Congratulation, your local Selenium hub is running.

4 Starting Testing

You can start testing by sending your test script to: http://yourmachinenameorIP:4444/wd/hub. Make sure it is reachable from the outside!

5 Optional: Scaling Your Nodes

Each node has one browser, so if you need more nodes of a certain browser, you can scale with docker-compose. With multiple nodes you can run tests in parallel. For example, if you want 3 Chrome browsers:

   sudo docker-compose up -d --scale chrome=3
   docker_hub_1 is up-to-date
   Starting docker_chrome_1 ... 
   Starting docker_chrome_1 ... done
   Creating docker_chrome_2 ... done
   Creating docker_chrome_3 ... done

   sudo docker-compose ps
         Name                 Command           State           Ports         
   ---------------------------------------------------------------------------
   docker_chrome_1    /opt/bin/entry_point.sh   Up                            
   docker_chrome_2    /opt/bin/entry_point.sh   Up                            
   docker_chrome_3    /opt/bin/entry_point.sh   Up                            
   docker_firefox_1   /opt/bin/entry_point.sh   Up                            
   docker_hub_1       /opt/bin/entry_point.sh   Up      0.0.0.0:4444->4444/tcp

6 Optional: Installing a Hub with “Live-view” Through VNC

If you want to watch your test case live for debugging purpose, you can use the following docker-compose.yml:

hub: 
 image: selenium/hub:3.8.1
 environment:
   - TZ=Europe/Amsterdam
   - GRID_TIMEOUT=90
 ports:
   - 4444:4444

firefox:
 image: selenium/node-firefox-debug:3.8.1
 links:
   - hub:hub
 environment:
   - TZ=Europe/Amsterdam
   - SCREEN_WIDTH=1600
   - SCREEN_HEIGHT=900
 ports:
   - 5901:5900

chrome:
 image: selenium/node-chrome-debug:3.8.1
 links:
   - hub:hub
 environment:
   - TZ=Europe/Amsterdam
   - SCREEN_WIDTH=1600
   - SCREEN_HEIGHT=900
 ports:
   - 5900:5900
 volumes:
   - /dev/shm:/dev/shm
 privileged: true

Some side notes in case you follow this step:

  • Notice that you are using debug versions and you are mapping the network ports of the browser images
  • You need a VNC-client like Tigervnc, VNC Viewer for Google Chrome or any other favorite client of your choice
  • For Chrome you use as an address: localhost:5900 (or machinename/ip:5900) with password “secret”
  • For Firefox you use as an address: localhost:5901 (or machinename/ip:5901) with password “secret”
  • You cannot scale using this configuration
  • Be aware that VNC is not a secure protocol, you might not want to open this port for the world

Congratulations you have finished setting up a local docker Selenium hub. The next how-to is How to setup a Local Selenoid hub. You find an overview of all the how-tos and the structure on the ATS 2 How-to’s page. We advise you to follow the predefined structure.