Create otel_logging_supported_config feature tracking metric.

[franciscovalentecastro]

Description

Create otel_logging_support feature tracking metric.

{
    Module: "logging",
    Kind:   "service",
    Type:   "otel_logging",
    Key:    []string{"otel_logging_supported_config"},
    Value:  "true / false",
}

Related issue

b/390671495

How has this been tested?

Checklist:

• Unit tests
  • Unit tests do not apply.
  • Unit tests have been added/modified and passed for this PR.
• Integration tests
  • Integration tests do not apply.
  • Integration tests have been added/modified and passed for this PR.
• Documentation
  • This PR introduces no user visible changes.
  • This PR introduces user visible changes and the corresponding documentation change has been made.
• Minor version bump
  • This PR introduces no new features.
  • This PR introduces new features, and there is a separate PR to bump the minor version since the last release already.
  • This PR bumps the version.

[quentinmit]

This doesn't actually check if the processor is supported, only if it might be supported.

Instead of doing all this work to separately validate, I would just clone the config, set the experimental flag, and see if generating causes an error:

func (uc *UnifiedConfig) OTelLoggingSupported() bool {
  uc2 := uc.DeepCopy(ctx)
  if uc2.Logging == nil {
    return false
  }
  if uc2.Logging.Service == nil {
    uc2.Logging.Service = &Service{}
  }
  uc2.Logging.Service.OTelLogging = true
  _, err := uc2.GenerateOtelConfig(ctx)
  return err == nil
}

[quentinmit]

If you wanted it per-pipeline, you could do

        pipelines, err := uc.Pipelines(ctx)
        if err != nil {
                return nil, nil, err
        }
        for name, pipeline := range pipelines {
                _, _, err := pipeline.otelComponents(ctx)
                supported[name] = err == nil
        }

[franciscovalentecastro]

I decided to only check the whole config and not consider individual pipelines for the current PR.

IMO, feature tracking about individual pipelines would not be very helpful for our goal (getting statistics of OTel logging supported configs), since it would require several additional metric labels to describe the pipeline in detail (which receivers, processors or features are unsupported for each pipeline).

I think it would be simpler to track specific unsupported receivers or processors, not tied to a specific pipeline. We can consider if this data is needed in the future. I consider this additional labels about which specific feature is not supported is out of scope of this initial task / PR and could added later if need.

[quentinmit]

This needs to be the Context from the unit test, not context.Background(). It looks like that needs to be passed into ExtractFeatures.

[quentinmit]

Your current diff will cause the logging log level to override the metrics log level. I think we should stick with the existing behavior of only using the metrics log level, which you could do with

logLevel := "info"
if uc.Metrics != nil && uc.Metrics.Service != nil && uc.Metrics.Service.LogLevel != "" {
  logLevel = uc.Metrics.Service.LogLevel
}

[franciscovalentecastro]

Done.

[quentinmit]

This is unnecessary; it's valid to iterate over a nil map.

[franciscovalentecastro]

Removed the uc.Metrics.Receivers != nil. Done.

[quentinmit]

This only needs to be if uc.Metrics != nil; subscripting a nil map is valid.

[franciscovalentecastro]

Removed the uc.Metrics.Receivers != nil. Done.