Set Up a Local Docker Selenium Hub

Last modified: November 19, 2024

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

Mendix does not deliver support for the local Selenium solutions.

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, which is why using this version of Selenium for the Docker images is recommended

Installing Your Hub and Nodes with Docker-Compose

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

Create a folder or directory to place your docker-compose file

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

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.

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

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.

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!

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

By default the hub only accepts a maximum of 5 sessions to run in parallel at a time, even if you configure more, see the official documentation.

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 set up a Local Selenoid hub. You find an overview of all the how-tos and the structure on the ATS 2 How-tos page. We advise you to follow the predefined structure.