Use bitwise combination for metrics options

[xiang17]

Exploring option improvement after discussion here #431 (comment)

Changes

Use bitwise combination for metrics options.

Pro:

• More granular control on every single metrics.

Con:

• A ton of options to be maintained. Not much to worry about if using default config, which is enabling all flags.
• Old issue still remains: it might be counterintuitive to have .AddRuntimeMetrics() as enabling all options as default, and after adding an option, say .AddRuntimeMetrics(options => { options.GcEnabled = true; }), all options other than GcEnabled will be disabled.

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #

[reyang]

This seems over complicated, especially considering some metrics' availability is dependent on the runtime version.

[reyang]

I wonder if we can simply start without any options - e.g. AddRuntimeInstrumentation() will just give you everything that's available to the current runtime/platform. Later if we want to introduce options, we can, and that's not a breaking change.

[xiang17]

I wonder if we can simply start without any options - e.g. AddRuntimeInstrumentation() will just give you everything that's available to the current runtime/platform. Later if we want to introduce options, we can, and that's not a breaking change.

Do you mean remove all the options?

In the current implementation, that's the default behavior if you don't specify any options: https://github.com/open-telemetry/opentelemetry-dotnet-contrib/tree/main/src/OpenTelemetry.Instrumentation.Runtime#step-2-enable-runtime-instrumentation-at-application-startup

[reyang]

I wonder if we can simply start without any options - e.g. AddRuntimeInstrumentation() will just give you everything that's available to the current runtime/platform. Later if we want to introduce options, we can, and that's not a breaking change.

Do you mean remove all the options?

In the current implementation, that's the default behavior if you don't specify any options: https://github.com/open-telemetry/opentelemetry-dotnet-contrib/tree/main/src/OpenTelemetry.Instrumentation.Runtime#step-2-enable-runtime-instrumentation-at-application-startup

I asked this because I saw ActiveTimerCount under the threading options. I don't know if Timer has a direct relation to threading despite the fact that .NET grouped it under the System.Threading namespace.

Overall I think it could take time to design these options and it requires a good understanding of usage scenario. I feel a good starting point is to have nothing configurable.

[cijothomas]

Agree to have no configurability in the 1st release. Adding the turn off flag later is not a breaking change.