In this article, I will go over the technical details on how in Eucalyptus, we used Selenium to simulate a large number of cloud user workload in order to ensure the quality of user experience in the new Eucalyptus user console.
As covered in my previous blog, Eucalyptus is coming out with a new user console, that is browser-based and intuitive to use, thus playing a key role in promoting the cloud adoption among IT organizations and enterprises. But, the challenge was to ensure that this brand-new user console would be ready for handling the real-world workload when released out in the wild. The answer to this challenge was to simulate the activities of 150 cloud users using Selenium, an open source tool for automating web application testing.
How to Automate an Online User
The first step was to download Selenium IDE for Firefox. Selenium IDE is a must-to-have GUI tool for automating clicks and input-submits on a web application. After installing Selenium IDE on your computer, you can start Selenium IDE from Firefox’s Tools menu:
When started, Selenium IDE opens up its own separate window:
Notice the red dot on the top-right corner of Selenium IDE. When clicked, Selenium IDE will start recording all the activities you perform on the web-browser — every link you click and every input you type on the browser will be recorded as command-lines on Selenium IDE as seen below:
What Selenium IDE allows you to do is to replay the recorded activities, such as clicking and typing, on the browser in the exact same order that they were performed.
But, soon you will notice that when replayed on Selenium IDE, it tends to fly through all the clicks in lighting speed so that the replayed activities often result in failures — the browser and web application cannot keep up with the speed of the clicks performed by Selenium IDE.
In order to prevent such cases, you will need to manually step through the record activities and insert various “pause-and-check” points using ‘waitForElementPresent’ command. For instance, when there is a command ‘click link=Delete’, I would put ‘waitForElementPresent link=Delete’ command prior to the click command to ensure that the page will fully loaded and the link ‘Delete’ is indeed present on the page before allowing Selenium IDE to execute the command ‘click link=Delete’. Later I learned that for every ‘click’ command, it is always a good habit to throw in the ‘waitForElementPresent’ command.
After verified that the recorded action is repeatable via Selenium IDE at its full speed, the next step is to export the action into a Selenium Python WebDriver format:
The result of the export above is a script file that describes the recorded Selenium action in a Python’s unittest format:
Once have the script exported, you can run the recorded action on a remote Selenium server without having to open up a web-browser. In other words, now you can simulate an online user doing the exact same recorded action on a web-browser by simply running the Python script generated by Selenium IDE.
Remote Selenium Server Configuration
Before running the script, you will need to configure a machine to run a remote Selenium server, which will behave like a web-client. The steps are on a Ubuntu machine, you will execute the following commands:
sudo apt-get -y update
sudo apt-get -y install default-jre
sudo apt-get -y install xvfb
sudo apt-get -y install firefox
sudo apt-get -y install python-pip
pip install selenium
Xvfb :0 -ac 2> /dev/null &
nohup java -jar selenium-server-standalone-2.25.0.jar &
After running the commands above, you will have a Ubuntu machine capable of running the exported Python Selenium script, which then, simulates an online user opening up a Firefox browser and performing the recorded clicks.
Creating a Flexible, Reusable Testing Tool
Now, your task is to produce many exported Python Selenium scripts for all activities on the web application that will be used as building blocks for creating different user behaviors and workflows.
The first collection of Python Selenium scripts I produced was to visit every single landing page on the Eucalyptus user console. The second collection of Python Selenium scripts was to create cloud resources under the default setting. Having those two sets of Python Selenium scripts allowed me to construct complicated user interactions on the web application. For instance, with a bit of shuffling of the scripts, I could build up a user scenario where the online user would visit the keypair page, create a new keypair, visit the dashboard page, visit the security group page, create a new security group, revisit the dashboard page, and so on.
The next task was to consolidate all the scripts into one library file, getting rid of static values in the variables and breaking down the actions in the scripts into functions. Having a such unified library enables test-writers to stitch and arrange these functions together to construct whole new user scenarios as needed.
When examining the Eucalyptus user console test framework se34euca, you will see that the main library file ‘lib_euca_ui_test.py’ contains the functions that are exported from Selenium IDE, where each function describes a very specific action to perform on the web console. The files ‘testcase_*.py’ list the arrangements of those functions to form simple, or complex user behaviors. Finally, the files ‘runtest_*.py’ are the executables of those test cases that take input of the target web console environment.
Now that you have a way to convert a Ubuntu machine into a Selenium server and have the Selenium test framework checked into a GitHub repository, you have a way to launch the Selenium test as a cloud instance — using se34euca as an example, the steps are:
Step 1. Launch a cloud instance on a Ubuntu image.
Step 2. Convert the Ubuntu image into a Selenium server by running the configuration commands above, or running the installer in se34euca.
Step 3. Git clone se34euca.
Step 4. Run the test case of your choice.
Step 5. Terminate the instance when the test is finished.
Of course, you can easily automate the step 2, 3, and 4 to wrap the entire process into a single scripted operation. Then, with a help of a cloud infrastructure, such as AWS or Eucalyptus, simulating 150 user can be as simple as launching 150 instances to run the script on each instance by feeding the parameter as user-data.
For those who are interested in creating a framework for testing your own web application, please feel free to check out the Eucalyptus user console test framework se34euca at:
for a reference, and leave a comment if you have any questions or suggestions.