Thresholds on http_req_duration{expected_response:true} error on v0.38.x

[mstoykov]

Brief summary

If you make a threshold on http_req_duration{expected_response:true} (or any other predefined metric with submetric, which currently is only this one) you will get back an error

ERRO[0000] sub-metric with params 'expected_response:true' already exists for metric http_req_duration: http_req_duration{expected_response:true}

originally reported on the k6 slack

k6 version

v0.38.0 to v0.38.2

OS

all

Docker version and image (if applicable)

No response

Steps to reproduce the problem

run

export let options = {
  thresholds: {
    'http_req_duration{expected_response:true}': ['avg<400', 'p(95)<800', 'p(99)<2000']
  },
}
export default () => { }

Expected behaviour

It works

Actual behaviour

You get

ERRO[0000] sub-metric with params 'expected_response:true' already exists for metric http_req_duration: http_req_duration{expected_response:true}