Calculate requests per second from json report

[Paxa]

I would like to get req/sec value from json report, I try to run script for 10 seconds and check difference between first time and last time in json report, I get 7847 ms, and I got very different result then terminal output

http_reqs..................: 38            3.799899/s

From my script

Total requests: 38
exec time: 7847 ms
req/sec: 4.842615012106537

Then I try to save start time and end time in my benchmark:

import { Gauge } from "k6/metrics";
var startCounter = new Gauge("start_counter");
var endCounter = new Gauge("end_counter");

export default function() {
  startCounter.add(Date.now());
  // my bench code
  endCounter.add(Date.now());
};

And I got better results:

exec time: 9890
req/sec: 3.8422649140546006 <-- almost good

Is there a better way to do it?

[na--]

@Paxa, I'm not completely sure what you're trying to do, can you explain in some more detail?

Regarding the metric timestamps when you output them to a JSON file, they represent the times when the response was received and processed. So, even if you make an HTTP request at t=0, if it takes 2 seconds to receive its response, you're going to see t=2s as the JSON metric timestamp. So, to calculate the req/s, you probably just need to divide the number of request metrics in that JSON file by the duration you specified for the test run.

If you just need the requests per second in a machine readable format, you might want to follow #1168. This PR would allow the exporting of all of the metrics you see in the end-of-test summary as a JSON file, so you don't need to process each individual metric to get the summary.