[feature request] Expose .NET Garbage Collection mode/configuration parameters

[baronfel]

Component

OpenTelemetry.Instrumentation.Runtime

Is your feature request related to a problem?

Today we can monitor the runtime characteristics of the GC (heaps, sizes, durations, etc) but we don't get any information about how the GC is configured to help us interpret those metrics.

What is the expected behavior?

A metric for the mode should be exported. This would probably be non-varying over the lifetime of the monitored process.

Which alternative solutions or features have you considered?

The application could export this metric.

Additional context

No response

Tip

_{React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it. Learn more here.}

[martincostello]

Seems a reasonable ask from a user perspective.

I'd suggest opening a parallel issue in the open-telemetry/semantic-conventions repository for how the new metric would work, possible values, etc. For example dotnet.gc.collections is defined there, and then we implement it here:

opentelemetry-dotnet-contrib/src/OpenTelemetry.Instrumentation.Runtime/RuntimeMetrics.cs

Lines 127 to 130 in 14678e2

	meter.CreateObservableCounter(
	"process.runtime.dotnet.gc.collections.count",
	GetGarbageCollectionCounts,
	description: "Number of garbage collections that have occurred since process start.");

Once the behaviour is agreed we can add it in.