Getting started with Gatling – Part 1

With the need to do some more effective load testing I am getting started with Gatling. Why Gatling and not JMeter? I have not used either so I don’t have a valid opinion. I made my choice based on:

• reduced GUI dependency
• newer code base
• documentation conciseness
• personal preference to scala vs straight java
• some blog posts including:
  • https://blog.flood.io/stress-testing-jmeter-and-gatling/
  • https://octoperf.com/blog/2015/06/08/jmeter-vs-gatling/
  • http://badmoodperf.blogspot.com.au/2014/01/gatling-vs-jmeter-fact-checking.html

Working through the Gatling Quickstart

Next step is working through the basic doc: http://gatling.io/docs/2.2.1/quickstart.html#quickstart. Pretty simple and straightforward.

Moving on to the more advanced tutorial: http://gatling.io/docs/2.2.1/advanced_tutorial.html#advanced-tutorial. This included:

• creating objects for process isolation
• virtual users
• dynamic data with Feeders and Checks
• First usage of Gatling’s Expression Language (not rly a language o_O)

The most interesting function:

object Search {
    val feeder = csv("search.csv").random
    val search = exec(http("Home")
                .get("/"))
                .pause(1)
                .feed(feeder)
                .exec(http("Search")
                .get("/computers?f=${searchCriterion}")
                .check(css("a:contains('${searchComputerName}')", "href").saveAs("computerURL")))
                .pause(2)
                .exec(http("Select")
                .get("${computerURL}"))
                .pause(3)
}

…Simulation‘s are plain Scala classes so we can use all the power of the language if needed.

Next covered off the key concepts in Gatling:

• Virtual User -> logical grouping of behaviours ie: Administrator(login, update user, add user, logout)
• Scenario -> define Virtual Users behaviours ie: (login, update user, add user, logout)
• Simulation -> is a description of the load test (group of scenarios, users – how many and what rampup)
• Session -> Each virtual user is back by a Session this can allow for sharing of data between operations (see above)
• Feeders -> Method for getting input data for tests ie: login values, search and response values
• Checks -> Can verify HTTP response codes and capture elements of the response body
• Assertions -> Define acceptance criteria (slower than x means failure)
• Reports -> Aggregated output

Last review for today was of presentation by Stephane Landelle and Romain Sertelon,  the authors of Gatling:

Next step is to implement some test and figure out a good way to separate simulations/scenarios and reports.