Whats the best approach to create user surge and drop over time?

[Ito]

So I have a simulation which consists of three different scenarios and it looks like:

setUp(slowScenario.inject(rampConcurrentUsers(1) to (Config.numberOfSlowUsers) during (Config.rampUpDuration minutes))
.protocols(httpconf),
normalScenario.inject(rampConcurrentUsers(1) to (Config.numberOfNormalUsers) during (Config.rampUpDuration minutes))
.protocols(httpconf),
fastScenario.inject(rampConcurrentUsers(1) to (Config.numberOfFastUsers) during (Config.rampUpDuration minutes))
.protocols(httpconf))
.maxDuration(Config.scenarioDuration minutes)
.assertions(global.successfulRequests.percent.is(100))

Given that I am running the test for eight hours, I’d like to create a 20% surge in the amount of users at the end of
each hour which will decline after a set time. For example if I am running 1000 users, after 50 minutes I’d like to gradually/randomly add
another 200 users. when I reach an hour, those 200 users will drop gradually/randomly and I will be back to my 1000 users.

Any examples, approaches, links, etc would be highly appreciated!

[Ito]

If anyone is interested in getting an answer for this question, I’ve also post it on Stack overflow with a bit of an update.

https://stackoverflow.com/questions/59073221/how-can-i-create-a-gatling-simulation-that-peaks-spikes-every-hour-and-returns-t

[jarrowwx]

Posted a reply to StackOverflow. Short answer: build one injection profile that strings together all the different steps that make up the full duration of the test. You can do this in a loop using a function that returns a list. See SO for pseudo-code.

[Ito]

Thank you very much, an excellent and elegant solution.

[Ito]

I am probably doing something incorrectly here as I am not getting the expected result.

I tweaked Johns suggestion a bit as inject requires a T parameter followed by multiple parameters.
If I am running the following code I am not getting the expected behavior, I get one ramp up followed by a ramp down as can be seen by the screenshot:

setUp(*scenario.*inject(rampUsers(10) during (1 minute),sInjection(1): _*)

.protocols(httpconf)).maxDuration(3 minutes)

[jarrowwx]

I believe you are doing an expression that doesn’t have side-effects, but are expecting side-effects.

seq ++ xyz

is an expression, it does not modify the element on the left, it returns a new sequence that includes all of the elements. You want:

var seq = …
…
seq = seq ++ …

[Ito]

Thanks again for your help.

I am still unable to get the desired behavior and I am starting to think that it might be due to some settings elsewhere.

Here is my base scenario creation function:

def createScenario(name: String, feed: FeederBuilder, chains: ChainBuilder*): ScenarioBuilder = { scenario(name).feed(feed).forever() { exec(chains) } }

I than create different scenarios using my base createScenario function:

def createUsageScenario(scenarioName: String): ScenarioBuilder = { val scenario = createScenario(Config.testName + "_" + scenarioType, feeder, exitBlockOnFail { exec(executeAndValidate(RestApi.userLogin)) .exec(executeAndValidate(RestApi.transaction1)) .exec(executeAndValidate(RestApi.transaction2)) .during(30 seconds) { foreach("${parameters}", "parameter") { .exec(executeAndValidate(RestApi.transaction3)) .exec(executeAndValidate(RestApi.transaction4)) } } }) scenario }

I create the scenario and lastly the simulation:

`

var scenario1 = createUsageScenario(“scenario”)

setUp(scenario1.inject(nothingFor(1 second),sInjection(1): _*
).protocols(httpconf)).maxDuration(4 minutes)

def sInjection( hours : Int ) = {
var seq = Seq[OpenInjectionStep](rampUsers(10) during (30 seconds))
var i = hours
while ( i > 0 ) {
seq = seq ++ Seq(nothingFor(3 minutes))
seq = seq ++ Seq(rampUsers(10) during (30 minute))
i -= 1
}
seq
}

`

What I would expect to happen is a test that runs for four minutes, ramps up 10 users over 30 seconds, do nothing for 3 minutes and then ramp 10 users over 30 seconds.
But this is what I actually get:

Now even if I run the test without any function that generates the injection like:

setUp(scenario1.inject( rampUsers(10) during (30 seconds), nothingFor(3 minutes), rampUsers(10) during (30 minute) ).protocols(httpconf)).maxDuration(2 minutes)

I still get the above behavior. Its as if the ‘nothingFor’ continues to execute the scenario
and is completely ignored by the simulation setup.

[Ito]

If anyone is interested, I’ve resoled the issue using a different approach.
The solution is described here:

https://stackoverflow.com/questions/59073221/how-can-i-create-a-gatling-simulation-that-peaks-spikes-every-hour-and-returns-t/59193423#59193423