Expose Duration by Completed Span

[kbrockhoff]

Many development teams will want the ability to log or further process the duration of a particular remote call. It would be helpful to have this exposed by the public Span API.

[bogdandrutu]

It is very interesting to me to understand why logging this when you have tracing (probably I don't understand very well the use-case). I am moving this to specs because this affects the public API capabilities.

[kbrockhoff]

There are two use cases I can think of.

1. When creating a MeasureBatchRecorder at the end of span, recording a duration value that exactly matches the duration being used by the tracing system.

2. Application developers wanting to log duration along with other application specific info to their application's logs.

The typical enterprise developer will choose to write their own understanding layer rather than make the effort to understand how to use a framework as designed. Exposing this data will make it a little less tempting for them to write their own layer.

[kbrockhoff]

I am thinking about how to write an enhancement proposal to enable optional recording of full message payloads. This will be important to enterprise developers wanting to prove that their team is not at fault for a particular issue. This is kind of the same category as use case number 2 above.

[bogdandrutu]

We do have a duration exposed in the SDK but not in the API, is that enough to cover all your use-cases?

[kbrockhoff]

My objective is to have the duration recorded for the span exactly match the duration pushed to the metrics system. The change to end span which enables passing in the end timestamp provides a solution. The process is to record a timestamp, pass it to end span and then subtract the captured start timestamp to calculate the duration to record a measurement for.

Fixed by #571

[bogdandrutu]

Closing this as @kbrockhoff said is fixed. Consider to re-open if I made a mistake.