Metric support plans

Background

OpenTelemetry .NET SDK currently has a basic implementation of the Metric API. This was written as a prototype (when Metrics Specs were in early stages), and is not recommended for any production scenarios.

The OpenTelemetry specification for Metrics SDK is a work-in-progress, and has not declared stable.

OpenTelemetry .NET SDK currently plans to release v1.0.0 the tracing/context/baggage signals by Jan/Feb 2021. As the Metric API/SDK is part of same package as other stable signals, all Metric API/SDK will be removed from the 1.0.0 release, and will be released as a separate, pre-release version (like 1.1.0-alpha1). Once Metrics spec is declared stable, there will be a stable release (like 1.2.0) which adds Metrics support.

OpenTelemetry .NET Metric plans

OpenTelemetry .NET SIG has previously collaborated with .NET runtime team on the Activity API, which was enhanced to be compatible with OpenTelemetry Tracing API. We expect to continue to collaborate with .NET runtime team for Metrics work as well. .NET runtime team has already announced plans to provide a OpenTelemetry compatible Metric API in the .NET Runtime itself.

Timeline

The next major release from .NET is .NET 6 which is expected to GA on Nov 2021. As OpenTelemetry .NET Metrics will be built on top of Metric API exposed by .NET runtime, OpenTelemetry .NET Metric will also GA at Nov 2021. Starting June 2021, there will be preview releases. Even though the Metric support is releasing along with .NET6, the actual API will be an out-of-band package, similar to System.Diagnostics.DiagnosticSource package, and is expected to support all officially supported versions of .NET Core and .NET Framework.(except .NET Framework older than 4.6.2)

[cijothomas]

Update: 1.2.0-rc2 got released (with huge perf improvement for Metrics) 1.2.0 stable, as soon as spec for Metrics SDK is stable.

[cijothomas]

Is there any sort of enumerated list of remaining features?

Will create one soon and mark with milestones as well.

This is the official compliance matrix: https://github.com/open-telemetry/opentelemetry-specification/blob/main/spec-compliance-matrix.md#metrics

For quick reference, here’s what we are missing:

1. UpDownCounter/ObservableUpDownCounter - trying to make it happen in .NET runtime itself. See https://github.com/open-telemetry/opentelemetry-dotnet/issues/2362
2. Advanced view configuration (to change aggregation itself, add more attributes/tags from Baggage) - https://github.com/open-telemetry/opentelemetry-dotnet/issues/2619, https://github.com/open-telemetry/opentelemetry-dotnet/issues/2618
3. Exemplars https://github.com/open-telemetry/opentelemetry-dotnet/issues/2527
4. MinMax for Histograms https://github.com/open-telemetry/opentelemetry-dotnet/issues/2560
5. Exponential Histograms (spec is still experimental)