How do I make this work? EL and Session variables.

Gatling (Open-Source)
1

Hi

Fairly new to Gatling and a little confused about how to make use of EL and Session variables that are not strings. I’ve read the docs, but there must be something that I don’t understand. Hopefully somebody can point me in the right direction. Basically, how can I get something like this to work?

“”"
import java.util.UUID

import io.gatling.core.Predef._
import io.gatling.core.session.Expression
import io.gatling.core.structure.{ChainBuilder, ScenarioBuilder}
import io.gatling.http.Predef._
import io.gatling.http.protocol.HttpProtocolBuilder
import io.gatling.http.request.builder.HttpRequestBuilder

import scala.concurrent.duration._

class MySimulation extends Simulation {

val httpConf: HttpProtocolBuilder = http.baseURL(AppConfig.baseUrl).disableCaching

val feeder: Iterator[Map[String, Any]] = Iterator.continually(Map(
“USER_ID” → scala.util.Random.alphanumeric.take(11).mkString,
“RESOURCE_IDS” → Seq.fill(10)(UUID.randomUUID)))

val requestChain: List[ChainBuilder] = List(
exec(getUser("${USER_ID}")),
exec(getResources("${RESOURCE_IDS}")))

val testScenario: ScenarioBuilder = scenario(“MySimulation”).forever(feed(feeder).exec(requestChain))

setUp(testScenario.inject(atOnceUsers(AppConfig.userCount))).protocols(httpConf).maxDuration(1 minutes)

def getUser(userId: String): HttpRequestBuilder =
http(“getUser”)
.get(s"/user/$userId")

def getResources(resourceIdsExpression: Expression[List[String]]): HttpRequestBuilder = {
???
}
}
“”"

2

Is anybody able to confirm that what I’m trying to do is possible or not? Any pointers to some examples out on the web?

Any help appreciated. Thanks.

3

No, it’s not. You can pass a List of HttpRequestBuilders but not an Expression.

4

Yes, which is working fine for me. However, I’m unable to obtain a List from a session variable when I try and I’ve seen in the docs that I should be using the Session. So I’m a little lost.

Is there a way to construct a chain or list of dependent HTTP actions and then pass them for execution? All with access to state from previous requests and session variables? Even lists.

And also to obtain a List from a feeder?

5

You don’t get it.

Having something like def getResources(resourceIdsExpression: Expression[List[String]]): HttpRequestBuilder wouldn’t work.
The resources method takes HttpRequestBuilder*. It’s not possible to build the HttpRequestBuilders at runtime, based on each Session’s data.
What you can do is have static HttpRequestBuilders resolve each Session’s data.

6

Thanks. Yes, I’m very sure I don’t get it. :blush:

That’s what I thought I was doing. I thought I was building static execution chain. I guess not. I know I can’t dynamically build HttpRequestBuilders at runtime.

Any tips or examples on how to do this static resolution of values as I’m attempting in my example?

I want a statically defined execution chain, but I want the request values to be dependent on session values from a feeder and previous requests in the session.

7

Have you gone through the documentation? Even the tutorials show how to use Gatling EL. Then, also have a look at the Session page.

8

Yes, I’ve read it all. I can already use simple EL Strings like the tutorial. That works no problem. I’m trying to resolve a List of values from a feeder.

I’ve basically followed the same pattern as Step 01 of the tutorial. In the tutorial,.exec is called with a list Search, Browse, Edit.

I’m trying to call .exec with a list getUser, getResources.

9

Maybe I can only use EL with Strings? So should I be building my JSON or lists of request parameters etc in my Feeder and then reading them in EL?

In the documentation, what types are these: