MetricsLayer — Add additional event fields as KeyValue pairs to a recorded metric

[jnicholls]

Feature Request

MetricsLayer — Add additional event fields as KeyValue pairs to a recorded metric.

Motivation

MetricsLayer is a great idea, to have events be able to be captured and exported as metrics. Brilliant. But, the current implementation only submits the metric name and value, and no associated KeyValue pairs to add context to the metric.

Proposal

It would be fantastic if other fields of the event were added as associated KeyValue pairs to the metric. Or, another specially named field specifically for MetricsLayer to inspect for optional KeyValue pairs.

[jtescher]

@jnicholls This sounds good! are you able to submit a PR to this effect?

[ymgyt]

If @jnicholls doesn't mind, I'd like to try this feature.

My understanding is that in the Metric api's Counter add operation spec says

This API MUST accept the following parameter:

• A numeric increment value.
• Attributes to associate with the increment value.

This feature allows you to associate the attributes with the metrics.

For example

tracing::info!(
  monotonic_counter.foo = 1,
  key_1 = val_1,
  "foo",
);

would export metrics with the attributes of key_1 = val_1.

[jtescher]

Resolved in #43