Gatling

Download Gatling from https://gatling.io/open-source

Make sure you have JDK 8 or new installed.

Unzip the file anywhere on your computer. Open up the new folder, and browse to the bin directory. From here.
1.) Run gatling.bat

Press 0 to choose the computerdatabase.BasicSimulation.
Description is optional and can be left blank.

Gatling will the script that you choose - which executes a basic load test against the Gatling computer database training site.

Results will be generated and looks like below

Gatling Project Setup

For Gatling we will write code in Scala.

Scala sits on top of the JVM, so any IDE which supports JVM we can use, I will be using IntelliJ

Gatling can be setup using Maven Build Tool

https://gatling.io/docs/current/extensions/maven_plugin/

Create Gatling Project with Maven Archetype

1.)Open CMD and type mvn archetype:generate

You will see message like below

2.) Choose a number or apply filter (format: [groupId:]artifactId, case sensitive contains): 1589:

Type gatling

Press 1 and then choose 35 as the version

groupId : com.gatlingTest

artifactId: myGatlingTest

version: 1.0-SNAPSHOT

for package press Enter to accept com.gatlingTest as the package name

Press Y to confirm

You will see message like

[INFO] Project created from Archetype in dir: C:\Users\T460\myGatlingTest
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 13:05 min
[INFO] Finished at: 2020-04-18T13:43:17+08:00
[INFO] Final Memory: 16M/291M

[INFO] ------------------------------------------------------------------------

3.) Now Import the created project in IntelliJ IDEA

This is how project Structure looks like

Now we need to Setup Scala on Machine

4.) Download Scala libraries from here

https://www.scala-lang.org/download/

Install Scala Plugin in IntelliJ and Restart

Now after restart ,Go to Scala file and you will see option on the top to "Setup Scala SDK" refer below Screenshot

Click Create Button select the version and Click OK

Right-click on the scala folder and click Mark Directory As -> Test Sources Root:

Also mark the main src folder as sources root as well

Add a Sample Gatling Script

Right-click on the scala folder and select New > Scala Package - give the package a name of computerdatabase . Right click on this folder and select New > Scala Class - give the class a name of BasicSimulation.

Sample Script

package computerdatabase

import io.gatling.core.Predef._
import io.gatling.http.Predef._
import scala.concurrent.duration._

class BasicSimulation extends Simulation {

val httpProtocol = http
.baseUrl("http://computer-database.gatling.io") // Here is the root for all relative URLs
.acceptHeader(
"text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
) // Here are the common headers
.acceptEncodingHeader("gzip, deflate")
.acceptLanguageHeader("en-US,en;q=0.5")
.userAgentHeader(
"Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:16.0) Gecko/20100101 Firefox/16.0"
)

val scn =
scenario("Scenario Name") // A scenario is a chain of requests and pauses
.exec(
http("request_1")
.get("/")
)
.pause(7) // Note that Gatling has recorder real time pauses

setUp(scn.inject(atOnceUsers(1)).protocols(httpProtocol))
}

To Run the script

In Terminal run

mvn gatling:test

This will execute a Gatling test using the Gatling Maven plugin

Importance of the packages

import io.gatling.core.Predef._
import io.gatling.http.Predef._

These imports are where the Gatling packages get imported - they are both required for all Gatling scripts.

import io.gatling.core.Predef._

This package provides Simulation , scenario, setup, exec

import io.gatling.http.Predef._

This package provides http, get

Note: We should always extend our Test class with Simulation class of the Gatling package, to make a Gatling script

Script has 3 areas

1.) HTTP Configuration

2.) Scenario Definition

3.) Load Scenario

HTTP Configuration

Here we setup the baseUrl and headers

Scenario Definition

These are the steps that the user will take when interacting with our application

Example: Go to API, wait , then second API , then Post some data

Load Scenario

This is where we set the load profile (such as the number of virtual users, how long to run for etc.) for our Gatling test.

Pause Time and Check Response Codes

.check(status.is(200)))

check(status.in(200 to 210))).pause(1,20)--> pause for a random time between 1 and 20 seconds

check(status.not(404),status.not(500))).pause(2000.millisecond)

Correlation in Gatling

The Check API in Gatling is used for 2 things:

1.) Asserting that the response contains some expected data
2.) Extracting data from that response

We can use JSONPath to extract some data from one call and save that in one variable then we can use that variable for subsequent API call now this process is called Correlation

check(jsonPath("$.name").is("some text")))

check(jsonPath("$[1].id").saveAs("variable")))

get("endpoint/${variable}").check(jsonPath("$.name").is("expected Name")))

How to write Methods

def getAll() = {
repeat(3) {
exec(http("Get All ").get("all").check(status.is(200)))
}
}

This way we can define methods

Here we can also give loop conditions like here repeat(3) will make 3 calls to all endpoint

Now we can use the above method for scenario

val scn = scenario("Code reuse")
.exec(getAll())

Gatling Feeders - for Test Data

CSV Feeders

We can create a csv file under src > test > resources folder

val csvFeeder=csv("data/csvFile.csv").circular

There are 4 ways to Load data in Gatling

.queue - default behavior: use an Iterator on the underlying sequence

.random - randomly pick an entry in the sequence

.shuffle - shuffle entries, then behave like queue

.circular - go back to the top of the sequence once the end is reached

Custom Feeders

By Using Custom Feeders we can create test data directly in our code

Load Simulation

Sample Scenario
1.) Do nothing for 5 seconds
2.) Start up with 5 users
3.) Start 10 users within 10 seconds

Snippet

setUp(scn.inject(nothingFor(5),atOnceUsers(5),rampUsers(10).during(10))).protocols(httpConf)

Other ways

constantUsersPerSec (rate) during (duration)- Here users will be injected at constant rate, defined in seconds

rampUsersPerSec(rate1) to (rate2) during (duration)- Inject users from rate 1 to rate 2.

Example:

setUp(scn.inject(nothingFor(1),atOnceUsers(15),constantUsersPerSec(10).during(5),

rampUsersPerSec(1) to (50) during(20))).protocols(httpConf)

Example:

setUp(scn.inject(nothingFor(1),atOnceUsers(150),constantUsersPerSec(100).during(5),
rampUsersPerSec(1) to (500) during(20))).protocols(httpConf)

JVM Heap

JVisualVM