Distributed tracing with open telemetry#100
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elizabetheonoja-art merged 3 commits intoJul 18, 2026
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…h-opentelemetry Add OpenTelemetry trace context propagation
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Motivation
Add end-to-end, OpenTelemetry-compatible W3C Trace Context propagation for off-chain services to improve observability and enable correlation across MQTT publishes, ingestion, and dashboard traces.
Ensure trace creation is safe and performant by validating incoming traceparent, rejecting all-zero ids, and generating local ids without depending on external collectors.
Surface simple health indicators in the dashboard (P99 latency, invalid contexts, exporter health) to meet the critical-path latency target and support canary/blue-green rollout decisions.
Description
Add meter-simulator/src/trace-context.js which provides parseTraceparent, createTraceContext, formatTraceparent, injectTraceContext, createBaggage, and calculateLatencyMs for W3C trace propagation and latency measurement.
Inject trace metadata into MQTT payloads by updating meter-simulator/src/mqtt-publisher.js to call injectTraceContext for usage, heartbeat, status, and to log publish-path latency; make service name configurable via observability.serviceName.
Expose observability configuration in meter-simulator/src/config.js and wire the service name into simulator entry points (simulate and send-reading) in meter-simulator/src/index.js.
Add Jest tests at meter-simulator/tests/trace-context.test.js covering traceparent creation/validation, parent-preservation, baggage encoding, and latency calculation, plus documentation docs/DISTRIBUTED_TRACING.md and a README observability section; update dashboard types/mock UI to show trace P99 and health signals.
Testing
Ran focused unit tests with npm test -- trace-context.test.js --runInBand, which passed (5/5 tests passed).
Performed syntax checks with node -c meter-simulator/src/mqtt-publisher.js and node -c meter-simulator/src/trace-context.js, which succeeded, and ran npx tsc --noEmit for dashboard type checks which succeeded.
Ran the full meter-simulator Jest suite (npm test -- --runInBand) and observed pre-existing unrelated failures in meter-device.test.js (fixture key size and timestamp/message-length expectations), which are not introduced by this change.
Attempted dashboard production build (npm run build) and it failed in this environment due to an external Google Fonts fetch error (network/font fetching issue), not code correctness.
Closes #63