How to create a Selenium Grid using Docker

This is a tutorial for creating a Selenium grid with Docker and Docker Compose using environment variables, above is the vid and below you will find some useful notes.

1. 1.

   Pre-reqs

   • Have Docker installed
     Have the code for our previous Galen Tests project or your own set of selenium tests locally
2. 2.

   What is selenium grid

   • Selenium grid is set of services or applications that allows us to create a testing environment in which we can test against different combinations of browsers and operating systems. You can also use it to run tests in parallel.
     Selenium grid consists of two parts. A hub that receives the selenium test commands, like click on this button or enter some text on a textfield, and passes them to the appropriate nodes.
   • And the nodes that register themselves against the selenium hub providing to it the information of each node’s running environment, like, the operating system (for example windows, linux or mac), browser (like firefox or chrome), the version, and so on. The nodes are the ones that run the tests against the actual browsers.
3. 3.

   How to use envioronment variables in Docker Compose

   • Create a .env file in the same folder as your docker-compose.yml file

       
     #Add some comments
     VARIABLE_NAME=value
       
     

   • Then, you can use the environment variable inside the docker-compose.yml file

       
     version: '3'
     services:
       my-service:
         image: image
         ports:
           - "2222:${VARIABLE_NAME}"
       
     

   • You can set the environment variables on your OS by calling export

       
     export HUB_SERVICE_PORT=5555
       
     

   • Or you can clear the environment variables by calling unset

       
     unset HUB_SERVICE_PORT
       
     

   • Check the current configurations for Docker Compose given the current values for the environment variables

       
     docker-compose config
       
     

4. 4.

   How to create a simple selenium grid with a hub and a node using Docker Compose

   • Configure the Selenium Hub

       
     version: '3'
     services:
       hub:
         image: "selenium/hub"
         environment:
           - GRID_HUB_PORT=${HUB_SERVICE_PORT}
         ports:
           - "${HUB_SERVICE_PORT}:${HUB_SERVICE_PORT}"
       
     

   • Configure the node (You can replace "BROWSER" below with "chrome" or "firefox" for example)

       
       selenium-node-BROWSER:
         image: "selenium/node-BROWSER"
         environment:
           - HUB_PORT_4444_TCP_ADDR=${HUB_SERVICE_URL}
           - HUB_PORT_4444_TCP_PORT=${HUB_SERVICE_PORT}
         depends_on:
           - "hub"
       
     

   • Start the hub and the nodes using docker compose

       
     docker-compose up
       
     

   • Check the selenium grid status given the ip for docker containers

       
     http://192.168.99.100:4444/grid/console
       
     

   • If you want to scale a particular service (you can replace "SERVICE-NAME=NUMBER-OF" below with "selenium-node-chrome" and "NUMBER-OF-INSTANCES" with 5 for example)

       
     docker-compose up --scale SERVICE-NAME=NUMBER-OF-INSTANCES
       
     

5. 5.

   Use galen to execute the tests against the local selenium grid

   • Run the galen tests using docker

       
     docker run -v $(pwd):/workdir -it local/galen test tests/ --htmlreport reports "-Dgalen.browserFactory.selenium.runInGrid=true" "-Dgalen.browserFactory.selenium.grid.url=http://192.168.99.100:4444/wd/hub"
       
     

6. 6.

   Resources

   Github link for the code

   Galen project for testing

   Selenium-Grid

   Wikipedia Selenium (software)

   Selenium Grid

   Docker hub - Selenium Containers

   Docker hub - Selenium Hub

   Docker hub - Chrome Node

   Docker hub - Firefox Node

   Desired Capabilities

   Configure Compose using environment variables

   Set environment variables with ‘docker-compose run’