Friday, July 20, 2012

Gatling made easy for SBT or/and Play2


These last few weeks, I took some time to understand a level deeper how SBT works and what it can provide. Since this post is not related to this learning trip (which was along existing blogs and wikis), I'll jump directly to the idea this new understanding gave me.
A while ago I started (and paused) a work on Gatling-Tool to have it integrated with Play 2.0 (see these posts here and here), this work has been refactored to better integrate with SBT.

What we'll find in this post

In this post, I'm gonna give you all tools in order to stress test you Web based application, either built upon Play 2.0, either only using SBT. By directly starting writing your tests rather than having to configure stuffs or to start others... So this post is composed of two parts:
  • How I built these tools (can be skipped -- definitively)
  • How to use these tools (it's probably the useful part)

Gatling shot 3 aside projects... for goods

This part is related to what was necessary to have gatling-tool easily integrated with SBT, and after with Play2.

Gatling SBT Test Framework

This project (on github) has a sole and simple goal, to implement the Test Interface (see) used by SBT to integrate new Test Framework (like was done for ScalaTest, Specs, JUnit, and...). This project contains only 2 classes and one convenient trait.


This class is one of the helper that avoid boilerplates in the future, because it starts the GatlingConfiguration stuff needed by Gatling-Tool to execute. This class requires two things "the path to the gatling configuration file" and "the path to the folder where will be stored the stress results".


This trait is another tool in hand that extends the com.excilys.ebi.gatling.core.Predef.Simulation provided by Gatling in order to add it two interceptors whose are pre and post. Those interceptors will be really useful in the future, in order to start/stop a server for instance (e.g. FakeServer in Play2).


This class is the real processor of the project. Actually, it's also the implementation of the interfaces declared by the SBT test framework which are Framework, Runner2 and some Fingerprints. Basically, what is done there are those tasks:
  • Create the gatling bootstrap based on sys properties
  • Declare fingerprint to discover Stress Test based on the parent class being be.nextlab.gatling.sbt.plugin.Simulation
  • Create the stress tests instances (only classes are handled for now) by reflection
  • Call the pre interceptor
  • Execute the stress test using the gatling api
  • Call the post interceptor
  • Generate the reports using the gatlin api

Gatling SBT Plugin

This project (here on github) aims to provide the basics to use the test framework easily within an SBT project
Its intent is to have testers able to write stress tests directly, just after having imported the module in SBT. 

It basically provides an SBT Configuration (gatling-test) that extends the SBT's Test one and one Command (takatak). The other goodies are settings which are common for all such stress tested projects using gatling. 
Those settings are essentially the conf file path, the result directories, the libraries (gatling ones principally) and so on. The last important thing that it does is to add the gatling test framework to the already existing list of test frameworks supported out of the box by SBT.

Gatling Play2 Plugin

This misnamed project (no more a Play2 plugin, neither a SBT one... but it's ok for now) brings only one little thing. It comes with a base implementation the custom Simulation declared in the Gatling Test Framework.

This base implementation is Play2 specific while creating a fake server and starting it in the pre interceptor, stoping it in the post one.

This will ease further tests in the Play2 environment.

Save Point

So far so good, if you read this you can now navigate the small projects that were necessary to do what we'll discuss in the next blog...

This one is already too long...