Improve Doc to Make the Tracing Context Example #575

[artsiomkaltovich]

Improve Doc to Make the Tracing Context Example ready to use out of the Box.

Please refer to issue #575

[tobz]

Currently, these changes don't actually compile when trying to run the doctests.

You'll need to add some of these dependencies to [dev-dependencies] and potentially update the enabled feature flags for some of the existing dev dependencies.

You can run cargo test -p metrics-tracing-context --doc locally to execute the tests while fixing the dependencies to ensure they're passing before requesting another review.

[tobz]

Suggested change

	//! use metrics_tracing_context::MetricsLayer;
	//! use metrics_tracing_context::TracingContextLayer;
	//! use metrics_tracing_context::{MetricsLayer, TracingContextLayer};

[artsiomkaltovich]

Hello @tobz.

I will fix the ci, if other changes are ok.

[artsiomkaltovich]

I've added dependencies, but I still got the following error:

---- metrics-tracing-context/src/lib.rs - (line 11) stdout ----
error[E0277]: the trait bound `PrometheusRecorder: Recorder` is not satisfied
   --> metrics-tracing-context/src/lib.rs:32:30
    |
24  | metrics::set_global_recorder(recorder).unwrap();
    | ---------------------------- ^^^^^^^^ the trait `Recorder` is not implemented for `PrometheusRecorder`
  

I've failed to understand why as Recorder as implemented for PrometheusRecorder and all dependencies seems up to date.

[tobz]

This probably needs to be a path dependency (see metrics-util above).

[artsiomkaltovich]

Yes, it is. I can't get why :)

Thank you.