Add add_resource_attributes config option to restore resource attributes in generated metrics

[iblancasa]

Description

Added a new configuration field to keep the resource attributes.

Link to tracking issue

Fixes #43394

[pjanotti]

The introduction of the connector.spanmetrics.excludeResourceMetrics feature gate changed the default behavior by excluding resource attributes from generated metrics.

Just checking understanding where we are and the path forward. The feature gate is created but in alpha so IsEnabled() should be returning false and at this time the resource attributes are still being generated by default. This PR is introducing a opt-in configuration that will be part of the component configuration going forward. Is that really the case? If it is intended as a temporary migration aid why the feature gate is not enough? Is the worry that the feature gate stages are going to be moved too fast?

[iblancasa]

Just checking understanding where we are and the path forward. The feature gate is created but in alpha so IsEnabled() should be returning false and at this time the resource attributes are still being generated by default. This PR is introducing an opt-in configuration that will be part of the component configuration going forward. Is that really the case?

The feature gate was introduced because the default behavior will change soon. This is nice and it is a good feature, but we found that this can break many users in our side (and very likely to other vendors). I'm implementing here a way to preserve the old behavior (so the users will not be affected) while new users will benefit from the new feature.

If it is intended as a temporary migration aid why the feature gate is not enough? Is the worry that the feature gate stages are going to be moved too fast?

If you check the 0.137.0 release notes, you will see there is an intention to make the feature gate stable very soon.

[Frapschen]

@iblancasa, Why don't we just disable the feature-gate manually?

[iblancasa]

@iblancasa, Why don't we just disable the feature-gate manually?

My concern is that this will be moved from alpha to beta in just one release. Are we expecting this speed from beta to stable?

[Frapschen]

I think it's fine to move from alpha to beta in one or two releases, but we can remain in the beta stage for a long time.

[iblancasa]

I think it's fine to move from alpha to beta in one or two releases, but we can remain in the beta stage for a long time.

I was thinking about this and think this option is still needed. There are many environments where you will not know which one are your resource attributes so, you cannot decided which ones add. The current behavior has worked well for us with those situations.

It is not just a migration path.

[Frapschen]

@iblancasa I can understand it

[iblancasa]

@open-telemetry/collector-contrib-maintainers can we merge this?

[lukaszgryglicki]

/easycla