How can I send multiple VUs request at the same time without using duration parameter?

My major goal - send (for example) 5 requests at the same moment. I found that I can not only set option vus: 5 and receive 5 simultaneous requests.

Is there a way to do so without tricks like using short duration and without limitations of RPS for VUs?

I just tried to set only option and it does not works properly. (example below)

export const options = {
  vus: 5,
};

Also I found that I able to run test for example for 30sec with VUs 5 and that works as the smallest ddos in web history (example below), but I would like to understand if there is a way to send just 5 requests at the same moment and nothing more.

export const options = {
  vus: 5,
  duration: '30s',
};

Solution

The closest funcitonalities in the most popular competitor load testing tools are called:

Quick lookup for both in context of k6 gives this article: Rendezvous with k6 which seems to be exactly what you're looking for.

Implementation example from the above article:

import http from 'k6/http';
import exec from 'k6/execution';
import { sleep } from 'k6';

export const options = {
    stages: [
        { duration: '40s', target: 20 },
        { duration: '2m', target: 20 },
        { duration: '5s', target: 0 },
    ],
};


export default function () {
    const rendezPeriod = 30000;
    /*Step1*/http.get('https://test-api.k6.io/public/crocodiles/1/');
    sleep(Math.random() * 5);
    /*Step2*/http.get('https://test-api.k6.io/public/crocodiles/2/');
    sleep(Math.random() * 5);
    /*Step3*/http.get('https://test-api.k6.io/public/crocodiles/3/');
    sleep(Math.random() * 5);
    /*Step4*/http.get('https://test-api.k6.io/public/crocodiles/4/');

    rendez(rendezPeriod);

    /*Step5*/http.get('https://test-api.k6.io/public/crocodiles/');
    sleep(Math.random() * 5);
    /*Step6*/http.get('https://test-api.k6.io/public/crocodiles/5/');
    sleep(Math.random() * 5);
    /*Step7*/http.get('https://test-api.k6.io/public/crocodiles/6/');
    sleep(Math.random() * 5);
    /*Step8*/http.get('https://test-api.k6.io/public/crocodiles/1/');
    sleep(Math.random() * 5);
}

// comment: quick implementation of rendezvous function in k6
//      stopping at periods, no user count ... yet
function rendez(rendezPeriod) {
    //comment: soFar is the time since the test started
    let soFar = new Date().getTime() - exec.scenario.startTime;

    //comment: calculate how much to wait until next rendez
    const waitTime = (rendezPeriod-(soFar%rendezPeriod))/1000;
    sleep(waitTime);
}