Creating random bursts of load?

Grafana k6 OSS Support
1

I’m looking for some advice on the best way to achieve the following load test

What we are looking to get is some random bursts of traffic to a specific api endpoint whilst maintaining a constant load on the rest of the api. Stages would look something like this, but a lot more of them

stages : [
  {target : 0, duration: '345s'},
  {target : 13, duration: '2s'},
  {target : 0, duration: '499s'},
  {target : 7, duration: '2s'},
  {target : 0, duration: '291s'},
]

What I have so far is

  • a function that generates the array of random stages based on (seeded for repeatability)
  • apply that array to the scenario
  • run the test

Given that the init context runs runs once per VU is this a sensible approach?

simplified sample of what the relevant init code looks like.

const burstStages = randomStages(burstParameters) // this function returns an array of stages which are used when setting up the scenario below

export const options = {
  scenarios: {
    BaseLoadScenario: {
      executor: "constant-vus",
      exec: "baseload",
      duration: testDuration,
      vus: 70,
    },
    BurstyScenario: {
      executor: "ramping-arrival-rate",
      exec: "burst",
      preAllocatedVUs: 30,
      startRate: 0,
      timeUnit: "1s",
      stages: burstStages
    },
  }
}
3

hi @steverivers95,

Given that the init context runs runs once per VU is this a sensible approach?

You can always only do it on the VU with __VU == 0 with an if, but IMO it doesn’t really matter.

You can probably test it and see how much it adds to the actual time to start. I expect that as long as you don’t make thousands of stages with thousands of VUs it will not matter all that much.

You can run with -v to see how fast VUs are started as well

Hope this helps!

5

Thanks for those suggestions, I will continue my investigation now I’m back from vacation :slight_smile: