fix(otlp): propagate _dd.p.tid from chunk root to all spans#2014
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DD tracers set `_dd.p.tid` (high 64 bits of 128-bit trace ID) only on the chunk root per RFC #85 — the Datadog backend reconstructs the full 128-bit ID at ingest. The OTLP mapper previously read the tag per span, so children landed with upper 64 bits zeroed and traces fragmented in pure-OTel backends. Resolve the chunk-level `_dd.p.tid` once in `map_traces_to_otlp` and apply it to every span. Per-span value still wins (forward-compat with tracers that propagate everywhere). Use `find_map` over the chunk so a malformed root tag falls back to the first parseable value in the chunk rather than poisoning the whole trace. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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…me calculated trace ID upper 64 bits on all spans in the chunk.
… trace_id field before checking the meta, in case we're already passing the full trace ID in.
mabdinur
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paullegranddc
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What does this PR do?
This PR updates the conversion of DD spans to OTLP spans to ensure all spans receive the high 64 bits of the 128-bit trace ID.
DD tracers set
_dd.p.tid(high 64 bits of 128-bit trace ID) only on the chunk root per RFC #85 — the Datadog backend reconstructs the full 128-bit ID at ingest. The OTLP mapper previously only read the tag per span, so child spans were emitted with upper 64 bits zeroed and traces fragmented in pure-OTel backends.The approach determines the chunk-level
_dd.p.tidonce inmap_traces_to_otlpand applies it to every span in the chunk. Per-span value still wins (forward-compat with tracers that propagate everywhere). Usefind_mapover the chunk so a malformed root tag falls back to the first parseable value in the chunk rather than poisoning the whole trace.Motivation
Performing end-to-end tests with dd-trace-py exporting OTLP spans surfaced this issue, which results in child spans recording different trace IDs than the local root spans. Notably, the only difference was that the high 64-bits of the 128-bit trace ID were zero'ed out.
Additional Notes
A system-test to cover this scenario is being simultaneously added in DataDog/system-tests#6973
How to test the change?
Regression tests have been added to
libdd-trace-utils/src/otlp_encoder/mapper.rs.