Correlate Rust logger lines to the active OTel trace + tee to tracing

[brentrager]

Problem

The Rust logger fabricated a uuid for traceId and carried no span id, so its lines couldn't be joined to the OpenTelemetry traces they belong to. And emit writes stdout-direct, so lines never reached @smooai/observability's OTLP logs appender (a tracing_subscriber::Layer) — even once that pipeline exists. Correlation fix, pearl th-de3805.

Solution

Two halves, depending on the OpenTelemetry API only (opentelemetry, trace feature) — never @smooai/observability (that would be circular):

1. Real trace/span ids. At log-build time, when an OTel span is active, override traceId with the span's real W3C trace_id and attach spanId (new spanId context key). No active span → the seeded uuid stays (prior behavior). New context::active_otel_trace_context() reads opentelemetry::Context::current().

2. Tee to the tracing facade. Each emitted line is also fired as a tracing event at the matching level (message → body, full JSON payload → log field), so the observability appender turns it into an OTLP log record. The event fires while the same OTel span is still active, so the appender's SDK logger stamps the record's trace_id/span_id from the current context — matching the ids this crate already put in the payload. Gated by a new otel_bridge option that defaults to the same env enablement as the observability logs pipeline (SMOOAI_OBSERVABILITY_ENDPOINT set and SMOOAI_OBSERVABILITY_DISABLED not truthy). Off → emit stays stdout-direct with zero tracing overhead.

Verification

cargo build, cargo clippy --all-targets (clean), cargo fmt --check (clean), cargo test — 20 passed (16 existing + 4 new). New tests/otel_correlation.rs:

• log_within_active_span_carries_real_trace_and_span_id — asserts traceId/spanId equal the active span's real ids. Actually verified, not just compiled: mutating the expected trace_id fails the test (real captured id 595170f2… vs the zeroed value).
• log_without_active_span_falls_back_to_uuid — no span → uuid traceId, no spanId.
• enabled_bridge_tees_line_to_tracing — one line → one tracing event at the matching level with the message as body (captured via a test subscriber layer).
• disabled_bridge_does_not_tee — off → no tracing events.

Branched off main (the repo's default work branch is a feature branch). No deploy. End-to-end join through the real observability appender was not exercised here — that lives in @smooai/observability (companion PR adds the logs signal) and the follow-up dogfood wiring.

🤖 Generated with Claude Code

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