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Setting up Selenium Grid on AWS EC2

By Grzegorz Szczutkowski | September 07, 2018 | Selenium Grid, Selenium WebDriver

 AWS become more and more popular if we talk about testing infrastructure. EC2's can be used for Selenium Grid infrastructure and it can work perfectly when our CI environment is also on EC2 (it is not required). In this article I will describe how to configure Linux image on EC2 to run Selenium Grid Hub/Node and how to minimise the AWS costs by running those machines from CI tool before tests run.

In the article I will not be going into details of configuration AWS infrastructure. I assume that you are able to create EC2 with Linux operating system and create dedicated configuration to make them accessible from your Continuous Integration (e.g. Jenkins) workers.

First of all we need two EC2 machines with any Linux operating system(I will use Ubuntu): first for Selenium Grid Hub and second for Selenium Grid Node. On both machines we have to download and install java and Selenium Server Standalone. 

sudo add-apt-repository ppa:webupd8team/java
sudo apt update; sudo apt install oracle-java8-installer
sudo apt install oracle-java8-set-default
wget http://selenium-release.storage.googleapis.com/X.XX/selenium-server-standalone-X.XX.X.jar
When java is installed and selenium server is downloaded we can focus on configuration Selenium Grid Hub machine. To make Selenium Grid runing automaticly after system startup we have to add the command for running Hub to /etc/rc.local file. Lets then add: 
sudo java -jar /home/ubuntu/selenium-server-standalone-X.XX.X.jar -role  hub -port 4444 &

Now after restarting this machine Selenium Grid Hub should be up and running. Just remember to add for this instance to security group that port 4444 should be opened for all Selenium Grid Nodes instances and workers to be able to ru tests.
Now lets focus on creating instance with Selenium Grid Node. First we have to update system, install X-server and Xvfb to be able to perform virtual graphic operations on the instance. 

sudo apt-get -y update
sudo apt-get -y install xvfb
sudo apt-get -y install xserver-xorg-core
sudo apt-get -y install xfonts-100dpi xfonts-75dpi xfonts-scalable xfonts-cyrillic

The next thing we need is to download and install Google Chrome and chrome driver: 

sudo add-apt-repository universe
sudo apt-get -y install google-chrome-stable
wget https://chromedriver.storage.googleapis.com/2.41/chromedriver_linux64.zip
sudo apt-get -y install unzip
unzip chromedriver_linux64.zip
rm chromedriver_linux64.zip
chmod +x chromedriver
sudo mv -f chromedriver /usr/local/bin

We are also installing Firefox and downloading geckodriver: 

sudo apt-get -y install firefox
wget https://github.com/mozilla/geckodriver/releases/download/vX.XX.X/geckodriver-vX.XX.X-linux64.zip
unzip geckodriver_linux64.zip
rm geckodriver_linux64.zip
chmod +x geckodriver
sudo mv -f geckodriver /usr/local/bin

To be able to use Xvfb we have to export DISPLAY to system variables: 

echo DISPLAY=":99" | sudo tee -a /etc/environment

Now we have to create two commands in /etc/rc.local file. The firs one is running the virtual screen and the second one run Selenium Grid Node with e.g. 4 instances of Firefox and 4 instances of Google Chrome. In that command we are also indicating where Selenium Grid Hub is located. 

Xvfb $DISPLAY -screen 0 1920x1080x24 -ac 2>&1 > /dev/null &
sudo -u ubuntu screen -d -m java -Dwebdriver.chrome.driver="/usr/local/bin/chromedriver" -jar /home/ubuntu/selenium-server-standalone-X.XX.X.jar -role  node -maxSession 4 -browser browserName=chrome,maxInstances=4 -Dwebdriver.gecko.driver="/usr/local/bin/geckodriver" -jar /home/ubuntu/selenium-server-standalone-X.XX.X.jar -role  node -maxSession 4 -browser browserName=firefox,maxInstances=4 -hub http://IP_OF_SELENIUM_GRID_HUB:4444/grid/register -port 5555 &

We have to set up security group of every the Selenium Grid Node on this way that Selenium Grid Hub should be able to access the Node via port 5555.
The only thing left is to starting the instances between running the tests 

SELENIUM_GRID_HUB="i-XXXXXXXXXXXXXX"
SELENIUM_GRID_NODE="i-XXXXXXXXXXXXXX"
aws ec2 start-instances --region "eu-west-1" --instance-ids $SELENIUM_GRID_HUB
aws ec2 start-instances --region "eu-west-1" --instance-ids $SELENIUM_GRID_NODE
aws ec2 wait instance-running --region "eu-west-1" --instance-ids $SELENIUM_GRID_HUB
aws ec2 wait instance-running --region "eu-west-1" --instance-ids $SELENIUM_GRID_NODE

and stopping them when the test have finished. 

aws ec2 stop-instances --region 'eu-west-1' --instance-ids $SELENIUM_GRID_HUB
aws ec2 stop-instances --region 'eu-west-1' --instance-ids $SELENIUM_GRID_NODE

Script for stopping instances should be run from e.g. Post build task plugin to prevent leaving EC2 instances running when the tests are failed.

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