Phase 4: Consensus tracing — round lifecycle, proposals, validations

[pratikmankawde]

PR Chain: #6436 → #6437 → #6438 → #6424 → #6425 → #6426 (this PR) → #6427 → #6433 / #6439
Base: pratik/otel-phase3-tx-tracing

High Level Overview of Change

Add distributed tracing for the consensus round lifecycle. Instruments four key points in RCLConsensus::Adaptor: proposal sending, ledger close, ledger accept, and validation sending. Each span carries domain-specific attributes (ledger sequence, consensus mode, proposer count, round duration).

Context of Change

Phase 4 of the OpenTelemetry distributed tracing project. Consensus is the core protocol loop — understanding its timing and behavior is critical for network health monitoring. The instrumentation uses the XRPL_TRACE_CONSENSUS macro which compiles to ((void)0) when telemetry is disabled, ensuring zero overhead in production builds without the feature.

Spans and attributes:

• consensus.proposal.send — round sequence
• consensus.ledger_close — ledger sequence, consensus mode
• consensus.accept — proposer count, round duration (ms)
• consensus.validation.send — ledger sequence, proposing flag

Design doc: OpenTelemetryPlan/ directory in this repo.

Type of Change

• New feature (non-breaking change which adds functionality)

API Impact

• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)

Test Plan

• Build with telemetry=ON and verify xrpld links.
• End-to-end: run a local network and verify consensus spans appear in Jaeger with correct attributes.
• Verify span hierarchy: consensus.ledger_close → consensus.accept.

Future Tasks

• Phase 5: Observability dashboards, spanmetrics, and production deployment config

[codecov]

Codecov Report

❌ Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.7%. Comparing base (f504d9b) to head (735ecd1).

Files with missing lines	Patch %	Lines
src/xrpld/app/consensus/RCLConsensus.cpp	72.7%	3 Missing ⚠️

Additional details and impacted files

@@                       Coverage Diff                       @@
##           pratik/otel-phase3-tx-tracing   #6426     +/-   ##
===============================================================
- Coverage                           79.7%   79.7%   -0.0%     
===============================================================
  Files                                851     851             
  Lines                              67941   67952     +11     
  Branches                            7587    7594      +7     
===============================================================
+ Hits                               54180   54184      +4     
- Misses                             13761   13768      +7     

Files with missing lines	Coverage Δ
src/xrpld/app/consensus/RCLConsensus.cpp	59.6% <72.7%> (+0.3%)	⬆️

... and 2 files with indirect coverage changes

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