Which Metrics to Use?

[lbeckman314]

Overview

It could be a nice addition to the README detailing which k6 metrics are of most interest in terms of measuring the performance of the data portals.

From the k6 docs —

What metrics to look at?

Each metric provides a different perspective on performance. So the best metric for your analysis depends on your goals.

However, if you’re unsure about the metrics to focus on, you can start with the metrics that measure the requests, errors, and duration (the criteria of the RED method).

• http_reqs, to measure
• http_req_failed, to measure error
• http_req_duration, to measure duration

Example Run

➜ k6 run login.js

          /\      |‾‾| /‾‾/   /‾‾/
     /\  /  \     |  |/  /   /  /
    /  \/    \    |     (   /   ‾‾\
   /          \   |  |\  \ |  (‾)  |
  / __________ \  |__| \__\ \_____/ .io

     execution: local
        script: login.js
        output: -

     scenarios: (100.00%) 1 scenario, 1 max VUs, 50s max duration (incl. graceful stop):
              * ui: 1 looping VUs for 20s (gracefulStop: 30s)

...

     browser_data_received.......: 40 MB  1.7 MB/s
     browser_data_sent...........: 152 kB 6.2 kB/s
     browser_http_req_duration...: avg=85.73ms  min=15µs     med=32.24ms  max=1.13s    p(90)=260.09ms p(95)=324.42ms
     browser_http_req_failed.....: 3.67%  ✓ 9        ✗ 236
     browser_web_vital_cls.......: avg=0.05025  min=0.005759 med=0.019946 max=0.233516 p(90)=0.114786 p(95)=0.168215
     browser_web_vital_fcp.......: avg=358.34ms min=99.5ms   med=379.4ms  max=786.19ms p(90)=529.38ms p(95)=644.96ms
     browser_web_vital_fid.......: avg=483.33µs min=99.99µs  med=100µs    max=3.7ms    p(90)=739.99µs p(95)=2.1ms
     browser_web_vital_inp.......: avg=22ms     min=16ms     med=16ms     max=40ms     p(90)=39.2ms   p(95)=40ms
     browser_web_vital_lcp.......: avg=358.71ms min=112.39ms med=267.89ms max=829.89ms p(90)=576.86ms p(95)=703.37ms
     browser_web_vital_ttfb......: avg=292.11ms min=42.29ms  med=161ms    max=843.5ms  p(90)=798.98ms p(95)=812.98ms
   ✓ checks......................: 0.00%  ✓ 0        ✗ 0
     data_received...............: 0 B    0 B/s
     data_sent...................: 0 B    0 B/s
     iteration_duration..........: avg=7.64s    min=7.46s    med=7.5s     max=7.96s    p(90)=7.86s    p(95)=7.91s
     iterations..................: 3      0.123272/s
     vus.........................: 1      min=1      max=1
     vus_max.....................: 1      min=1      max=1

Additional Resources:

• https://k6.io/docs/using-k6/metrics/: Previous k6 docs (nicer formatting!)