[Propagators] OTLP trace export carries ot.th/rv[APMAPI-2170] - #9062
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[Propagators] OTLP trace export carries ot.th/rv[APMAPI-2170]#9062MilanGarnier wants to merge 3 commits into
ot.th/rv[APMAPI-2170]#9062MilanGarnier wants to merge 3 commits into
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ot.th/rv (APMAPI-2170)
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ot.th/rv (APMAPI-2170)ot.th/rv[APMAPI-2170]
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Execution-Time Benchmarks Report ⏱️Execution-time results for samples comparing This PR (9062) and master. ✅ No regressions detected |
BenchmarksBenchmark execution time: 2026-08-21 09:34:59 Comparing candidate commit 4b6a5e8 in PR branch Found 0 performance improvements and 47 performance regressions! Performance is the same for 25 metrics, 0 unstable metrics, 110 known flaky benchmarks, 16 flaky benchmarks without significant changes.
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August 19, 2026 15:11
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| var otelTraceState = spanModel.Span.Context.OtelTraceState; | ||
| if (!StringUtil.IsNullOrEmpty(otelTraceState)) |
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When OTLP export is enabled with a supported injection configuration that omits tracecontext (for example, DD_TRACE_PROPAGATION_STYLE_INJECT=datadog), locally rooted probability-sampled traces still have a null OtelTraceState: TraceContext.SetSamplingPriority() only derives rv/th when IsW3CTraceContextInjectionEnabled() is true. Consequently this new serializer branch emits no traceState, so the advertised OTLP sampling metadata disappears for that configuration. OTLP export itself needs to be treated as a consumer when deciding whether to derive the state.
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| internal void WriteSpans(JsonTextWriter writer, in TraceChunkModel traceChunk, bool emitStartingComma) | ||
| { | ||
| var otelTraceState = traceChunk.SpanCount > 0 ? traceChunk.GetSpanModel(0).Span.Context.OtelTraceState : null; | ||
| var otlpTraceState = StringUtil.IsNullOrEmpty(otelTraceState) ? null : "ot=" + otelTraceState; |
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non-blocking: Is there a long-term plan to emit the entire tracestate field into the OTLP span rather than just the ot part? I suppose for efficiency reasons we only need to propagate the ot part for OTel probabilistic sampling to work but in the future this might be flagged as a missing feature if we don't do the whole tracestate
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| internal void WriteSpan(JsonTextWriter writer, SpanModel spanModel) | ||
| { | ||
| var otelTraceState = spanModel.Span.Context.OtelTraceState; | ||
| var otlpTraceState = StringUtil.IsNullOrEmpty(otelTraceState) ? null : "ot=" + otelTraceState; | ||
| WriteSpan(writer, spanModel, otlpTraceState); | ||
| } | ||
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| private void WriteSpan(JsonTextWriter writer, SpanModel spanModel, string? otlpTraceState) |
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Before merging, let's make sure to only have one WriteSpan method defined. Currently there is one that is only called in the product code (the 3-argument overload) and one that is only called in the test code (the 2-argument overload). If the otelTraceState already had the "ot=" prefix in the value, then the 2-argument overload would work, otherwise we should go with the 3-argument one.
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| internal void WriteSpan(JsonTextWriter writer, SpanModel spanModel) | |
| { | |
| var otelTraceState = spanModel.Span.Context.OtelTraceState; | |
| var otlpTraceState = StringUtil.IsNullOrEmpty(otelTraceState) ? null : "ot=" + otelTraceState; | |
| WriteSpan(writer, spanModel, otlpTraceState); | |
| } | |
| private void WriteSpan(JsonTextWriter writer, SpanModel spanModel, string? otlpTraceState) | |
| internal void WriteSpan(JsonTextWriter writer, SpanModel spanModel, string? otlpTraceState = null) |
| result.Links.Should().BeNullOrEmpty(); | ||
| } | ||
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| [Fact] |
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Why is this unit test being reverted?
zacharycmontoya
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This set of changes LGTM
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Summary of changes
Export the
ot=tracestate member in OTLP JSON and protobuf spans. (contains tracestate sampling datathandrv).Implementation details
Serialize the existing
OtelTraceStatevalue when present.Test coverage
Added focused JSON and protobuf serializer tests for present and absent values.
Other details
Stacked on #8983 which brings the support for otel tracestate sampling, and should be reviewed first.
System tests: TODO