[connector/datadog] Add config option for compute_top_level_by_span_kind

[liustanley]

Description:

Add config option for computing top level spans by span kind in the Datadog connector and exporter.

Link to tracking Issue:
#32005

Testing:

Documentation:

[mx-psi]

What would happen if I set compute_top_level_by_span_kind to true in the connector but not the exporter? What about the other way around?

[liustanley]

What would happen if I set compute_top_level_by_span_kind to true in the connector but not the exporter? What about the other way around?

compute_top_level_by_span_kind needs to be set wherever stats are being computed. By default, stats are computed in the connector but not the exporter, so this option needs to be set in the connector. If a customer is only using the exporter and disabled the noAPMStats feature gate, then this option would need to be set in the exporter. I plan on including this in the Datadog docs

[mx-psi]

If a customer is only using the exporter and disabled the noAPMStats feature gate, then this option would need to be set in the exporter. I

Oki, then I think we should allow users to set compute_top_level_by_span_kind on the exporter only if they have disabled the noAPMStats feature gate, and validate this during unmarshaling.

[liustanley]

Oki, then I think we should allow users to set compute_top_level_by_span_kind on the exporter only if they have disabled the noAPMStats feature gate, and validate this during unmarshaling.

Sorry I just caught a mistake while testing. If we only set compute_top_level_by_span_kind on the Datadog connector, the exporter will still use the old top-level spans logic and doesn't set span metrics correctly. When using the connector, compute_top_level_by_span_kind needs to be set on both the connector and exporter. When only using the exporter, compute_top_level_by_span_kind needs to be set in addition to the noAPMStats feature gate being disabled.

I'm not sure if there's a way to enforce this across components, but I'll document this usage in the Datadog docs.

[mx-psi]

Oki, then I think we should allow users to set compute_top_level_by_span_kind on the exporter only if they have disabled the noAPMStats feature gate, and validate this during unmarshaling.

Sorry I just caught a mistake while testing. If we only set compute_top_level_by_span_kind on the Datadog connector, the exporter will still use the old top-level spans logic and doesn't set span metrics correctly. When using the connector, compute_top_level_by_span_kind needs to be set on both the connector and exporter. When only using the exporter, compute_top_level_by_span_kind needs to be set in addition to the noAPMStats feature gate being disabled.

I'm not sure if there's a way to enforce this across components, but I'll document this usage in the Datadog docs.

@liustanley On this repository, I think we should mention this on

• the release note
• the configuration example
• (optional) an info-level log on the connector

We don't have a good way to validate this cross-component requirement, but we should at least mention it widely.