JMeter : SwitchControler or How to run a sampler with a certain percentage

Context:

• you want to run different parts of a Test plan a different rate
• you want to be sure one and only one of the samples occur thus you cannot use ThroughputController as you don’t have the guarantee that your sample will run

Example:

• You want to run 4 types of searches:
  • Search by Last Name
  • Search by Mail
  • Search by Phone Number
  • Search by Card Number
• You want to use the search result (so be sure it executed once)

SwitchControler or How to run a sampler with a certain percentage:

Create a Test Plan like this one:

• Important parts are:
  • JSR223 Sampler + Groovy
  • SwitchController which uses ${SWITCH_VALUE} as switch condition, depending on its value, Controller will execute one of the child elements that matches the Switch Value
  • 4 samplers (could be transaction controller or any other sampler)
• Content of JSR223 Sampler are the following:

// Array of values that contain the % repartition we want

int[] values = (int[])vars.getObject("RANDOM_VALUES");

if(values==null) {

    values =  [0,1,2,3,2,3,1,3,2,3] as int[];

    vars.putObject("RANDOM_VALUES",values);

}

// Increment that will be used in SwitchController value will be between 0 and 2

// because there are 3 TCs

Integer increment = (Integer)vars.getObject("INCREMENT");

if(increment==null) {

    increment = Integer.valueOf(0);

} else {

    increment = Integer.valueOf((increment.intValue()+1)%values.length);    

}

String value = Integer.toString(values[increment.intValue()]);



vars.put("SWITCH_VALUE", value);

vars.putObject("INCREMENT", increment);

SampleResult.setResponseData("SWITCH_VALUE from inside:"+value, null);

return "SWITCH_VALUE:"+value;

• Note the following:
  • JSR223 Sampler generates SWITCH_VALUE, a number between 0 and 3 (because there are 4 samples)
  • The percentages are held in RANDOM_VALUES array, note we have:
    • 10% of 0
    • 20% of 1
    • 30% of 2
    • 40% of 3
  • The generated number will decide which sampler is ran:
    • If 0 is generated, the first one will be run (Sampler-10%)
    • If 1 is generated, the second one will be run (Sampler-20%)
    • If 2 is generated, the third one will be run (Sampler-30%)
    • If 3 is generated, the fourth one will be run (Sampler-40%)
  • To use Groovy, just add groovy-all-VERSION.jar (in embeddable folder) in JMETER_HOME/lib folder
  • Note that you see in JSR223 Sampler a new feature of upcoming 2.9 version which allows Script (Specific to certain JSR223 implementations) to be compiled and cached increasing dramatically performances of Script code.

That’s it.

Result:

2 VUs with Loop of 50:

Conclusion:

As you can see coding custom code and using it in JMeter is rather easy but always remember:

• Only script when you don’t find the element
• Script efficiently and use the languages that perform well not ones that you master

About the author:

Philippe Mouawad is a developer, committer and member of the JMeter Project Management Committee at Apache.

He is also the co-author of the book Master JMeter : from load testing to DevOps.

He currently works as an Architect and technical expert for Ubik-Ingenierie where he leads among other things the development of UbikLoadPack a set of Commercial Plugins for Apache JMeter allowing to load test different protocols like MPEG-DASH, Http Live Streaming (HLS), HSS, HDS, GWT, JavaSerialization, Oracle applications.

About us:

• We provide professional services for Load Testing
• We’re strong contributors to JMeter and its eco-system
• Ubik Load Pack is a set of Enterprise Grade plugins for Apache JMeter. Our solutions are used by Big players
• Get a Free trial

1 Comment

• 

  Vincent DABURON

  on 3 January 2013

  I could use also a beanshell sampler to compute the Switch_value like this :

  BeanShell compute SWITCH_VALUE

  ================================

  rand = vars.getObject("P_RAND");

  if (rand == null) {

  rand = new java.util.Random(100);

  vars.putObject("P_RAND", rand);

  }

  int iAlea = rand.nextInt(100);

  if (0 <= iAlea && iAlea < 10) {

  // 10%

  sCase = "0";

  }

  if (10 <= iAlea && iAlea < 30) {

  // 20%

  sCase = "1";

  }

  if (30 <= iAlea && iAlea < 60) {

  // 30%

  sCase = "2";

  }

  if (60 <= iAlea && iAlea < 100) {

  // 40%

  sCase = "3";

  }

  log.info("sCase = " + sCase);

  vars.put("SWITCH_VALUE",sCase);

  ==============================

  The main advantage is that BeanShell is installed by default with JMeter

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