Add _dd.measured to spans when agent sampling is enabled

[BrynCooke]

The 2.x branch doesn't seem to be adding the _dd.measured attribute to spans. And the tests look incorrect.

The tests are now fixed and the attribute is added when enabling datadog agent sampling.

This will need backporting as the test is likely incorrect in 1.x.

It seems that this is working in 1.x because the spans are being set to _top_level, which automatically makes them measured.

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Complete the checklist (and note appropriate exceptions) before the PR is marked ready-for-review.

• Changes are compatible¹
• Documentation² completed
• Performance impact assessed and acceptable
• Tests added and passing³
  • Unit Tests
  • Integration Tests
  • Manual Tests

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Notes

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2. Configuration is an important part of many changes. Where applicable please try to document configuration examples. ↩

3. Tick whichever testing boxes are applicable. If you are adding Manual Tests, please document the manual testing (extensively) in the Exceptions. ↩

[router-perf]

CI performance tests

• connectors-const - Connectors stress test that runs with a constant number of users
• const - Basic stress test that runs with a constant number of users
• demand-control-instrumented - A copy of the step test, but with demand control monitoring and metrics enabled
• demand-control-uninstrumented - A copy of the step test, but with demand control monitoring enabled
• enhanced-signature - Enhanced signature enabled
• events - Stress test for events with a lot of users and deduplication ENABLED
• events_big_cap_high_rate - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity
• events_big_cap_high_rate_callback - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity using callback mode
• events_callback - Stress test for events with a lot of users and deduplication ENABLED in callback mode
• events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• events_without_dedup_callback - Stress test for events with a lot of users and deduplication DISABLED using callback mode
• extended-reference-mode - Extended reference mode enabled
• large-request - Stress test with a 1 MB request payload
• no-tracing - Basic stress test, no tracing
• reload - Reload test over a long period of time at a constant rate of users
• step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• step-local-metrics - Field stats that are generated from the router rather than FTV1
• step-with-prometheus - A copy of the step test with the Prometheus metrics exporter enabled
• step - Basic stress test that steps up the number of users over time
• xlarge-request - Stress test with 10 MB request payload
• xxlarge-request - Stress test with 100 MB request payload

[svc-apollo-docs]

✅ Docs preview has no changes

The preview was not built because there were no changes.

Build ID: cfe9a9917a13bbbb3a400d43

[bnjjj]

I think for 1.x we should not add this and just update the test to make sure it works properly.

[BrynCooke]

Agreed

[theJC]

This will set _dd.measured on ALL spans? If so, do we really want that, or just want certain subset of spans to be measured?

REF: DataDog/documentation#22774 (comment)

As for measured, that is intentionally undocumented as it must be used carefully, typically with help from our Support team. It allows span metrics to be generated for custom traces.

[abernix]

@theJC this is a good callout. we're going to revert this PR and for the moment, this configuration can be used:

   supergraph:
        attributes:
          "_dd.measured":
            static: 1

we'll at least update our docs.

[abernix]

@theJC: @BrynCooke has worked with @cgati to reach out to Datadog support to get advice on this. At the current time though, we believe not returning this option to enabled is preventing the proper functionality of the Datadog APM view on Router 2.x. Stay tuned (but let us know if you have any additional thoughts! :) )