Metric numVU is 0 in constant-arrival-rate scenario

[sabariarunkumar]

Brief summary

For the attached script, expected VU count metric is 1 in a consistent manner
But I could see its often dropping to 0.

This gives a misleading info that load is generated even without any virtual user/connection just by looking at the metric

Metric screenshot:
[

](url)

Script: https://gist.github.com/sabariarunkumar/a9ecf46d71cdc80bdd0e7b706fe93b79

k6 version

v2.1.0 (commit/83a87a41e2, go1.26.4, darwin/arm64)

OS

Mac

Docker version and image (if applicable)

No response

Steps to reproduce the problem

1. Configured a local prometheus
2. Set k6 to run the script with output type to prometheus
   ./k6-v2.1.0-macos-arm64/k6 run ../k6-dummy.js --log-format raw --user-agent sabu --insecure-skip-tls-verify --out experimental-prometheus-rw -v

Attaching the summary generated by k6

█ TOTAL RESULTS

checks_total.......: 14998   49.992171/s
checks_succeeded...: 100.00% 14998 out of 14998
checks_failed......: 0.00%   0 out of 14998

✓ status

HTTP
http_req_duration..............: avg=792.03µs min=256µs    med=745µs    max=10.79ms p(90)=1.03ms p(95)=1.22ms
  { expected_response:true }...: avg=792.03µs min=256µs    med=745µs    max=10.79ms p(90)=1.03ms p(95)=1.22ms
http_req_failed................: 0.00%  0 out of 14998
http_reqs......................: 14998  49.992171/s

EXECUTION
dropped_iterations.............: 3      0.01/s
iteration_duration.............: avg=1.03ms   min=330.66µs med=981.18µs max=11.1ms  p(90)=1.33ms p(95)=1.57ms
iterations.....................: 14998  49.992171/s
vus............................: 1      min=0          max=1
vus_max........................: 2      min=1          max=2

NETWORK
data_received..................: 2.1 MB 6.9 kB/s
data_sent......................: 960 kB 3.2 kB/s

Expected behaviour

Consistently providing numVu metric value as 1

Actual behaviour

Sporadically seeing the value of numVu metric as 0