How to concatenate the created resources in a list so I can delete them later in test as part of clean up?

Question

I'm performing the following code to get the response field from executing a gatling http request and appending it to a list but in response I see the list is mostly showing the same itemId. I wonder if this is because of concurrency ? I am making this list so I can capture the resources after each create operation call and at the end of test, can iterate over this list to perform a clean up/delete of items as in using "after" hook of gatling.

In simulation class:

var responseIdList = List[String]() 

val scenario1 = scenario(" TEST ")
        .exec(Create())
        .exec(session => {
            item = session("itemId").as[String].trim
            println("%%%%%%%%%%% item ID =====>>>>>>>>>> " + item)
            responseIdList = item :: responseIdList
            println("%%%%%%%%%%%  List =====>>>>>>>>>> " + responseIdList)
            session}
        )
 setUp(
    scenario1.inject(atOnceUsers(5))
)

Gatling action:

   def Create():HttpRequestBuilder= {

      http("CREATE API")
       .post(Host + "/items")
       .header("Authorization", "Bearer "+ token)
       .header("Content-Type", "application/json")
       .body(StringBody(
         """{ "name" : "Item1"
         |}""".stripMargin)).asJson
       .check(status.is(200))
       .check(jsonPath("$.itemId").saveAs("itemId"))

   }

Here is the response after executing above code:

    %%%%%%%%%%% item ID =====>>>>>>>>>> dc7e4024-c51e-46ce-93be-6ba1dad3679e
    %%%%%%%%%%% item ID =====>>>>>>>>>> 0bf84d48-ccea-4f10-93b3-ea464adcc952
    %%%%%%%%%%% item ID =====>>>>>>>>>> 072361b2-5c49-4641-a27c-c346c01dde99
    %%%%%%%%%%% item ID =====>>>>>>>>>> dc7e4024-c51e-46ce-93be-6ba1dad3679e
    %%%%%%%%%%% List =====>>>>>>>>>> List(0bf84d48-ccea-4f10-93b3-ea464adcc952, 072361b2-5c49-4641-a27c-c346c01dde99)
    %%%%%%%%%%% List =====>>>>>>>>>> List(0bf84d48-ccea-4f10-93b3-ea464adcc952, 0bf84d48-ccea-4f10-93b3-ea464adcc952, 072361b2-5c49-4641-a27c-c346c01dde99)

    %%%%%%%%%%% item ID =====>>>>>>>>>> dc7e4024-c51e-46ce-93be-6ba1dad3679e

    %%%%%%%%%%%  List =====>>>>>>>>>> List(0bf84d48-ccea-4f10-93b3-ea464adcc952, 0bf84d48-ccea-4f10-93b3-ea464adcc952, 0bf84d48-ccea-4f10-93b3-ea464adcc952, 0bf84d48-ccea-4f10-93b3-ea464adcc952, 072361b2-5c49-4641-a27c-c346c01dde99)

Even though on simulation of the scenario there were 5 different item Ids being created but somehow list is showing the same items. Is there a better data structure or option for me to use? Kindly advice as I'm a beginner in both gatling and scala .

Answer 1

Using a List and var global references is a wrong strategy because it's not threadsafe.

You should use vals and a java.util.concurrent.ConcurrentLinkedQueue:

import java.util.concurrent.ConcurrentLinkedQueue

   def Create():HttpRequestBuilder= {

      http("CREATE API")
       .post(Host + "/items")
       .header("Authorization", "Bearer "+ token)
       .header("Content-Type", "application/json")
       .body(StringBody(
         """{ "name" : "Item1"
         |}""".stripMargin)).asJson
       .check(status.is(200))
       .check(jsonPath("$.itemId").saveAs("itemId"))

   }

// EDIT: global threadsafe structure stored in an immutable reference
val responseIdList = new java.util.concurrent.ConcurrentLinkedQueue[String]() 

val scenario1 = scenario(" TEST ")
        .exec(Create())
        .exec(session => {
            // EDIT: local val here instead of global var
            val item = session("itemId").as[String].trim
            println("%%%%%%%%%%% item ID =====>>>>>>>>>> " + item)
            responseIdList.offer(item)
            // EDIT: print queue content
            println("%%%%%%%%%%%  List =====>>>>>>>>>> " + util.Arrays.toString(responseIdList.toArray))
            session}
        )
 setUp(
    scenario1.inject(atOnceUsers(5))
)