Question about exec.vu.idInTest

Grafana k6 OSS Support
1

Hi,
Is there a way to read data in a CSV file 1 row at a time? I tested it with exec.vu.idInTest
, however it cannot guarantee the order. Below is a simple script how did I test it. Assume the list is the csv file, it cannot guarantee to read one element per execution when multiple users running concurrently.

import http from "k6/http";
import exec from "k6/execution";

export const options = {
  scenarios: {
    PerVU: {
      executor: "shared-iterations",
      iterations: 10,
      vus: 10,
    },
  },
};

export function setup() {
  const name = [
    "a",
    "b",
    "c",
    "d",
    "e",
    "f",
    "g",
    "h",
    "i",
    "j",
    "k",
    "l",
    "m",
    "n",
    "o",
    "p",
    "q",
    "r",
    "s",
    "t",
    "u",
    "v",
    "w",
    "x",
    "y",
    "z",
  ];
  console.log("setup() function is executed!");
  return { name };
}

export default function (data) {
  let index = exec.vu.idInTest - 1;
  console.log(
    `The index # is ${index}, The VU: ${__VU}, Iteration number: ${__ITER}, name is No. ${index} in ${data.name[index]}`
  );
}

Below is the example, as you can see, exec.vu.idInTest couldn’t guarantee the uniqueness at each execution.

time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 8, The VU: 9, Iteration number: 0, name is No. 8 in i" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 4, The VU: 5, Iteration number: 0, name is No. 4 in e" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 7, The VU: 8, Iteration number: 0, name is No. 7 in h" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 5, The VU: 6, Iteration number: 0, name is No. 5 in f" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 1, The VU: 2, Iteration number: 0, name is No. 1 in b" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 0, The VU: 1, Iteration number: 0, name is No. 0 in a" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 6, The VU: 7, Iteration number: 0, name is No. 6 in g" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 8, The VU: 9, Iteration number: 1, name is No. 8 in i" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 3, The VU: 4, Iteration number: 0, name is No. 3 in d" source=console
time="2023-03-10T00:56:13-08:00" level=info msg="The index # is 9, The VU: 10, Iteration number: 0, name is No. 9 in j" source=console
3

Hi @alex

Can you try with exec.scenario.iterationInTest as mentioned in Data Parameterization?

import exec from "k6/execution";

export const options = {
    scenarios: {
        PerVU: {
            executor: "shared-iterations",
            iterations: 10,
            vus: 10,
        },
    },
};

export function setup() {
    const name = [
        "a",
        "b",
        "c",
        "d",
        "e",
        "f",
        "g",
        "h",
        "i",
        "j",
        "k",
        "l",
        "m",
        "n",
        "o",
        "p",
        "q",
        "r",
        "s",
        "t",
        "u",
        "v",
        "w",
        "x",
        "y",
        "z",
    ];
    console.log("setup() function is executed!");
    return { name };
}

export default function (data) {
    let index = exec.scenario.iterationInTest;
    console.log(
        `The index # is ${index}, The VU: ${__VU}, Iteration number: ${__ITER}, name is No. ${index} in ${data.name[index]}`
    );
}

Which guarantees it will only be used once:

INFO[0000] The index # is 0, The VU: 1, Iteration number: 0, name is No. 0 in a  source=console
INFO[0000] The index # is 1, The VU: 1, Iteration number: 1, name is No. 1 in b  source=console
INFO[0000] The index # is 2, The VU: 8, Iteration number: 0, name is No. 2 in c  source=console
INFO[0000] The index # is 3, The VU: 8, Iteration number: 1, name is No. 3 in d  source=console
INFO[0000] The index # is 5, The VU: 6, Iteration number: 0, name is No. 5 in f  source=console
INFO[0000] The index # is 9, The VU: 5, Iteration number: 0, name is No. 9 in j  source=console
INFO[0000] The index # is 8, The VU: 6, Iteration number: 1, name is No. 8 in i  source=console
INFO[0000] The index # is 4, The VU: 1, Iteration number: 2, name is No. 4 in e  source=console
INFO[0000] The index # is 6, The VU: 8, Iteration number: 2, name is No. 6 in g  source=console
INFO[0000] The index # is 7, The VU: 9, Iteration number: 0, name is No. 7 in h  source=console

If this is not working for your case, let us know.

Cheers!