Not able to use global vars

Grafana k6 OSS Support
1

In previous versions of K6 I was able to declare a global variable on the Init and use it anywhere on the code (on the default and also on external methods called from the default). For example:

(Example updated, thanks to @pearsone answer)

script.js

import { sleep } from 'k6';
import { externalMethod } from '../src/utils.js'

const vars = []

vars["URL"] = "https://test.k6.io";
vars["H1"] = "Hello!!";

export default function () 
{
  console.log(vars["H1"]);
  externalMethod();
  sleep(1);
}

utils.js

import http from 'k6/http';

export function externalMethod()
{
    console.log("executing externalMethod..");
    http.get(vars["URL"]);
}

Executing k6 run script.js

Ouput with k6:0.41.0

INFO[0000] Hello!!                                       source=console
INFO[0000] executing externalMethod..                    source=console
ERRO[0000] ReferenceError: vars is not defined
        at externalMethod (file:///scripts/src/utils.js:6:13(9))
        at file:///scripts/src/script.js:12:2(10)
        at native  executor=per-vu-iterations scenario=default source=stacktrace

Ouput with k6:0.36.0

INFO[0000] Hello!!                                       source=console
INFO[0000] executing externalMethod..                    source=console

running (00m01.6s), 0/1 VUs, 1 complete and 0 interrupted iterations
default ✓ [======================================] 1 VUs  00m01.6s/10m0s  1/1 iters, 1 per VU

On Test life cycle (k6.io) it mentions that we should declare the gloval vars on the init side, so I assume this is still possible. Am I right?

If not, I would like to confirm. The only way to follow a similar approach would be:

  1. Work with the external input on the init.
  2. Assign all that “data” to a json object on the setup an return it.
  3. Work with that object on the default method.

Thanks in advance! :slight_smile:

2

Testing with v0.41.0, this seemed to work:

import { group } from 'k6';

const vars = [];
vars["APP-URL"] = __ENV.K6_APP_URL;
vars["TESTID"] = 'TC01S';
vars["XXXX"] = 'XXXX';
vars["YYYY"] = 'YYYY';

export default function TC01() {
  group(vars["TESTID"] + '_99', function () {
    console.log(vars["APP-URL"])
  });
}

Output:

$ k6 run -e K6_APP_URL=www.hi.com script.js

INFO[0000] www.hi.com                                    source=console

The only difference I can see is the fact that you haven’t imported group from 'k6'

3

My example was not correct. :frowning:

I have updated it now, Thank you @pearsone

4

No worries.

I don’t think this is possible in ECMAscript. Is there a reason you can’t pass the variables into the functions?

e.g.,

entrypoint

import { externalMethod } from './utils.js'

var data = {"URL": "https://test.k6.io"}

export default function ()
{
  externalMethod(data["URL"]);
}

utils.js

import http from 'k6/http';

export function externalMethod(url)
{
    console.log("executing externalMethod..");
    http.get(url);
}
5

Of course I can, but for certain purposes I would like to use Global vars :slight_smile:

I know that it is not best practice but as I mentioned it was possible in previous versions and it is metioned on Test life cycle (k6.io) Init test stage “used To”.

6

Hi @andonima,

You seem to have been using a bug within k6 that was fixed in v0.40. You can found more info in this issue, but this was never suppose to work like it did before and is against what module as suppose to do. If you need to have global variables use the globalThis global object.

Hope this helps you

p.s.

metioned on Test life cycle (k6.io) Init test stage “used To”.

I would argue this is not what that part of the “Used to” is supposed to mean, but I definitely can see how it can be confused, so will try to reword it. Thanks for mentioning it :bowing_man:

7

Maybe “Role” or “Purpose” would be a less confusing description than “Used To”

8

metioned on Test life cycle (k6.io) Init test stage “used To”.

Wow! Good call out.

When I wrote, I was thinking of a truncation of sentences like “The function is used to operate the …”. Never thought how this could be interpreted as “Now you’re just somebody that I used to know”. But it definitely could, so we should find a less ambiguous title. There are much less ambiguous ways. I like “Purpose” as pearsone just mentioned.

10

Done! Thank you.