[anna-git]

What Does This Do

Exports the span propagation tags (_dd.p.dm, _dd.p.ksr, _dd.p.tid, ...) and baggage-as-tags items as string attributes in OTLP trace export (protobuf and JSON), mirroring the Datadog mappers:

• OtlpTraceProto / OtlpTraceJson MetaWriters now write Metadata.getBaggage(), which was computed but never serialized. Span tags win on a key clash, so OTLP attribute keys stay unique.
• Propagation tags are requested only for the local root span (ROOT_PROPAGATION_TAGS), like TraceMapperV0_4/V0_5; child spans don't carry _dd.p.* (no per-span _dd.p.tid).

Motivation

With DD_TRACE_OTEL_EXPORTER=otlp, remote and adaptive sampling rules are applied (priority, _dd.rule_psr are exported), but the sampling decision maker _dd.p.dm never was. The Agent then falls back to a default decision maker, so the backend doesn't count the traffic as rule/adaptive-sampled and adaptive sampling can't converge for the service.

This complements DataDog/datadog-agent#58471, which preserves _dd.p.dm from OTLP span attributes (or t.dm from a tracestate dd= member). The .NET equivalent is DataDog/dd-trace-dotnet#9498.

Additional Notes

• Validated with a local DDOT collector and remote/adaptive sampling rules: before, traces reached intake with _dd.p.dm:-4; with this change the root span is expected to carry the rule's decision maker (-11 remote user rule / -12 remote adaptive rule), which the Agent keeps with [trace-agent] Preserve tracer sampling decision maker in OTLP receiver datadog-agent#58471. The end-to-end run with this exact build is still to do.
• Unit tests: new propagationTagsAreWrittenOnTheLocalRootSpanOnly in OtlpTraceProtoTest and OtlpTraceJsonCollectorTest (fail before, pass after). :dd-trace-core:spotlessCheck couldn't run locally because the Eclipse p2 site used by the Groovy formatter was down; changed files were checked with google-java-format 1.36.1.
• Follow-ups, not in this PR:
  • Locally started traces have no dd= tracestate member, so the OTLP trace_state doesn't carry t.dm.
  • Partial flushes: chunks without the local root span carry no _dd.p.*, while the Datadog mappers put them on the first span of each chunk.

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors
• Once approved, use merge queue to merge the PR

Jira ticket: N/A

🤖 Generated with Claude Code

[dd-octo-sts]

🟡 Java Benchmark SLOs — Performance SLO warning (near threshold)

Suite	Status
Startup	🟡 warning

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.99 s	13.89 s	[-0.2%; +1.6%] (no difference)
startup:insecure-bank:tracing:Agent	12.92 s	12.92 s	[-0.9%; +0.8%] (no difference)
startup:petclinic:appsec:Agent	17.74 s	17.56 s	[+0.0%; +2.0%] (maybe worse)
startup:petclinic:iast:Agent	16.85 s	17.65 s	[-8.8%; -0.2%] (maybe better)
startup:petclinic:profiling:Agent	17.27 s	17.44 s	[-2.0%; +0.0%] (no difference)
startup:petclinic:sca:Agent	17.81 s	17.63 s	[-0.1%; +2.1%] (no difference)
startup:petclinic:tracing:Agent	16.65 s	16.64 s	[-1.0%; +1.2%] (no difference)

Commit: 89694562 · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.