Store execTime metric in nanoseconds

[ssncferreira]

What this PR does / why we need it:

Enhancement: store execTime result summary statistic metric in nanoseconds.

Which issue(s) this PR fixes:
Fixes #4949 (comment)

Special notes for your reviewer:

Checklist

• Documentation added
• Tests updated
• Add an entry in the CHANGELOG.md about the changes.

[owen-d]

This LGTM, but I'd like to see if it'll affect Grafana's usage of this API

[owen-d]

@ivanahuckova Do you think this will negatively affect Grafana's usage of our statistics?

[ivanahuckova]

Kind of. When we are processing result's statistic, we add a unit to the value, so we can then display it in nice way. E.g:

if it is more than 60 sec, we will show 1 minute:

if it is less than 1 sec, we will show ms

So if we change this, we will need to add logic to check if the value is in ns (integer) or sec(float) which will be slightly hacky, but possible. 🙂

So if you decide to change this, could you create issue in Grafana repo to change the logic there as well.

[ssncferreira]

Thank you @ivanahuckova 🙂
As already discussed, both statistic time values execTime and queueTime will be returned by the HTTP API in second as float.

[ssncferreira]

Grafana uses the returned statistics from the HTTP API and expects time values to be in second as float. As discussed and in order to avoid subsequent changes to Grafana, this PR will be closed and the conversion of queueTime will be handled in PR #5052