JSON.parse SyntaxError when running a duration test

[gewfy]

This issue is related to #339 and #340
But I've reproduced this without using stages or rambda. The error happens if you set any form of duration e.g. k6 run --duration 5s test.js

This tiny test:

import { check } from 'k6';
import http from 'k6/http';

export default function () {
  const res = http.get('https://api.dev.peachworks.com/v1/products');

  check(res, {
    'status is 200': res => res.status === 200
  });

  const products = JSON.parse(res.body).results;

  check(products, {
    'products is not empty': products => products.length > 0
  });
}

The above test produces the SyntaxError problem but no check errors:

[ragnarlonn]

@liclac @gewfy This issue appears at the end of the test, and if you use a script that either idles the VUs at the end, or sleeps after the last HTTP request of the iteration, the bug is not triggered (e.g. running a 5-second test and not issuing any HTTP requests past the first 4 seconds of the test will not trigger it).

This makes it seem like it may be a matter of a faulty teardown order somewhere, in a code path that only happens when you use --duration (--iterations n does not trigger the bug).

This the smallest script that will trigger the EOF error (k6 run --duration 5s script.js):

import http from 'k6/http';

export default function () {
  const res = http.get('https://api.dev.peachworks.com/v1/products');
  const products = JSON.parse(res.body).results;
}

Now, if I add a sleep anywhere after the HTTP request the error disappears:

import http from 'k6/http';
import { sleep } from "k6";

export default function () {
  const res = http.get('https://api.dev.peachworks.com/v1/products');
  // sleep(1); // error goes away
  const products = JSON.parse(res.body).results;
  sleep(1); // error goes away
}

...but if I move the sleep to before the HTTP request the error is still triggered:

import http from 'k6/http';
import { sleep } from "k6";

export default function () {
  sleep(1); // error still there
  const res = http.get('https://api.dev.peachworks.com/v1/products');
  const products = JSON.parse(res.body).results;
}

So, my conclusion is that the error is triggered when duration ends while k6 either still has HTTP requests to make (as in when there is a sleep before the HTTP request), or is in the process of making a request (as in when there is no sleep at all, which means the HTTP request is the likely place the VU code will be when duration ends - because it is the longest-running function call in the script)

Wild guess: could it be something introduced with the new buffer pool code -
b002f2c ?

[liclac]

This looks like an issue wrt how VUs are scheduled, I'll do some poking around.

[elimatripathy]

I am using k6 to check performance for one of our endpoints and the endpoint requires using access token so the script fails very intermittently at line var obj_accesstoken = JSON.parse(res_accesstoken.body, sleep(1.0));
with error as

ERRO[0004] SyntaxError: EOF
running at parse (native)
default at file:///Users/tripate/Documents/k6_perf_POC/notificationServiceRequest.js:32:33(22)
at native executor=constant-vus scenario=default source=stacktrace

I tried adding sleep after http call and after json parse still the exception happens . Below is my code
var payload = { email: username, password: password }; var res_accesstoken = http.post(url, JSON.stringify(payload), { headers: { "Content-Type": "application/json" } }, sleep(1.0)); //console.log("Endpoint response for token is = ", res_accesstoken); try { var obj_accesstoken = JSON.parse(res_accesstoken.body, sleep(1.0)); } catch(err) { //console.error(res_accesstoken.body could not be parsed as JSON. Received:\n${res_accesstoken.body}); var res_accesstoken = http.post(url, JSON.stringify(payload), { headers: { "Content-Type": "application/json" } }, sleep(1.0)); var obj_accesstoken = JSON.parse(res_accesstoken.body, sleep(1.0)); } var token = obj_accesstoken["data"]["access_token"];
I don't understand if this is okay because my checks at the end are working expected and no threshold error is shown to user

[na--]

@elimatripathy, please do not comment in issues that have been closed for more than 5 years... Moreover, the GitHub issues are not the place to ask such questions, please use the community forum at https://community.k6.io/