Improve the init stage docs

[dbonchev42]

Brief summary

console.log() prints twice

k6 version

1.4.0 - commit/a9f9e3b28a, go1.25.4

OS

Ubuntu 20.04.6

Docker version and image (if applicable)

No response

Steps to reproduce the problem

Run a k6 script with console.log()

const string = 'str';
console.log(string);

export default function () {

}

Expected behaviour

Printed once in the console

Actual behaviour

Printed twice in the console

...
     scenarios: (100.00%) 1 scenario, 1 max VUs, 10m30s max duration (incl. graceful stop):
              * default: 1 iterations for each of 1 VUs (maxDuration: 10m0s, gracefulStop: 30s)

INFO[0000] str                                           source=console
INFO[0000] str                                           source=console


  █ TOTAL RESULTS 

    EXECUTION
...

[inancgumus]

Hi @dbonchev42, thanks for reporting. Is this the entire script, and how do you run it?

const string = 'str';
console.log(string);

export default function () {

}

[dbonchev42]

Hi @inancgumus, yes this is the entire script. Sorry I forgot to share how to run it. Sharing script execution and the whole output i get

dbonchev@dbonchev-u20:~/repo/rms/performance-testing/rms-performance-tests-k6$ k6 run script.js 
INFO[0000] str                                           source=console

         /\      Grafana   /‾‾/  
    /\  /  \     |\  __   /  /   
   /  \/    \    | |/ /  /   ‾‾\ 
  /          \   |   (  |  (‾)  |
 / __________ \  |_|\_\  \_____/ 

     execution: local
        script: script.js
        output: -

     scenarios: (100.00%) 1 scenario, 1 max VUs, 10m30s max duration (incl. graceful stop):
              * default: 1 iterations for each of 1 VUs (maxDuration: 10m0s, gracefulStop: 30s)

INFO[0000] str                                           source=console
INFO[0000] str                                           source=console


  █ TOTAL RESULTS 

    EXECUTION
    iteration_duration...: avg=5.44µs min=5.44µs med=5.44µs max=5.44µs p(90)=5.44µs p(95)=5.44µs
    iterations...........: 1   5490.945431/s

    NETWORK
    data_received........: 0 B 0 B/s
    data_sent............: 0 B 0 B/s




running (00m00.0s), 0/1 VUs, 1 complete and 0 interrupted iterations
default ✓ [======================================] 1 VUs  00m00.0s/10m0s  1/1 iters, 1 per VU

[inancgumus]

Hi @dbonchev42, the documentation should have been more precise on this. The init code runs once (or more in some cases) to initialize. For example, if you run this script with two VUs, you'll see three console.log outputs; the first is from the initialization part. Other than that, each VU runs the init code actually only once. The solution is to use the setup stage.