An Introduction to Load Testing With Gatling

Testing is the most crucial part of an application development process to ensure high-quality, impeccable features. Therefore, along with the standard, integration, functional, and load tests, browser tests are also important in a company’s testing strategy. After developing the application, the substantial final task is to write and implement load tests.

To perform the load tests efficiently, a new tool, known as Gatling Tool, has been preferred by many organizations. Gatling is an open-source load testing framework for analyzing and measuring the performance of applications. It is an easy-to-install tool where simulations and scenarios are coded in a simple domain-specific language (DSL). An attractive point of this tool is that you can just define and write up your performance test scenarios in a similar way to other test automation frameworks. You can thus generate readable and easy to maintain performance test code.

Positives

• High performance
• Scenario recorder and developer-friendly DSL
• Ready-to-present HTML reports

Supported Technologies

• HTTP
• JMS
• WebSockets
• Server-sent events

Keeping it Portable

• Gatling’s installation process is simple and doesn’t require machine-by-machine basis installation. Gatling libraries are available from a Maven repository.
• Gatling is built on Scala, and the simulations also must be written in Scala
• Gatling also provides us elegant and meaningful reports that are easy to analyze and understand what exactly is going on with the application.
• Gatling integrates easily with Jenkins through the Jenkins-plugin and runs your tests through Gradle and Maven with the help of maven-plugin and gradle-plugin.

Let’s Have Deeper Look

Basically, Gatling can be structured in 4 different parts:

1. HTTP protocol configuration — This defines the base URL that runs against your tests. Also, you can define other configurations such as user agent, language header, connection, and so on.
2. Headers definition — This provides the headers with a request that has to be sent to the server. This is relevant because the headers add a bit of a load on servers that are testing.
3. Scenario definition — The core of your test! A Scenario includes a group of actions (like GET, POST, etc.) that are executed to simulate user’s interaction with the application.
4. Simulation definition — This defines the load (number of users) that concurrently executes your scenario for a period.

Simulation

A simulation is a description of the load test, which describes how user populations runs; which scenario they execute and how new virtual users are injected. Here is an example of simulation definition:

Steps to Install Gatling

Step 1

Download Gatling <Gatling 2.1.7 latest> based on your operating system (you need to have a JDK installed for Gatling; it requires, at least, JDK7u6)

Step 2

Extract zip and navigate to the <D:\gatling-charts-highcharts-bundle-2.1.7\bin> and run recorder (recorder.bat)

Step 3

Once the recorder is launched, the following GUI lets you configure how requests and responses are recording.

Step 4

Configure the recorder. All you need to do is start recorder and configure your browser to use Gatling Recorder’s proxy.

Step 5

Recording the scenario:

• Browser your application URL
• When you open the application, it will automatically start running the scenario
• When the scenario playing is finished, click stop in the Recorder interface

Note: Try to act like a real user. Don’t jump from one page to another immediately without taking the time to read. This will make your scenario closer to real users’ behavior.

Step 6

The Simulation will get generate in the folder user-files/ simulations/ computer database of your Gatling installation, under the name BasicSimulation.scala.

Step 7

Running Gatling:

• Launch the script located in the bin directory:
  • On Windows: %GATLING_HOME%\bin\gatling.bat
  • On Linux/Unix: $GATLING_HOME/bin/gatling.sh
• You will see a menu with the simulation
• Choose a simulation number (it depends on your stimulation name):

[2] computerdatabase.BasicSimulation

Step 8

When the simulation is finished, the console will display a link to the HTML reports

Analysis

Reports will be generated in the Results folder:

Gatling gives a complete analysis of each and every request with graphical representation (charts) in HTML files. Hence, they are portable and can be viewed on a web browser of any device.

Reports give us these details:

• Active users over time
• Response time distribution
• Response time percentiles over time
• Requests per second over time
• Responses per second over time

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