Phase 2: Complete RPC tracing — interface, macros, attributes, tests

[pratikmankawde]

PR Chain: #6436 → #6437 → #6438 → #6424 (this PR) → #6425 → #6426 → #6427 → #6433 / #6439
Base: pratik/otel-phase1c-rpc-integration

High Level Overview of Change

Complete the RPC tracing instrumentation started in the POC phase. Adds the missing shouldTraceLedger() method to the Telemetry interface, introduces XRPL_TRACE_PEER and XRPL_TRACE_LEDGER macros, enhances RPCHandler with duration and error span attributes, and adds a unit test for telemetry config parsing.

Context of Change

Phase 2 of the OpenTelemetry distributed tracing project. The POC (Phase 1) established the core infrastructure — build system integration, Telemetry interface, NullTelemetry stub, SpanGuard RAII, and basic RPC tracing macros. This phase fills in the gaps: the shouldTraceLedger() method was declared in Setup but missing from the virtual interface, and the trace macros for peer and ledger domains were not yet implemented. The RPCHandler span was also missing duration_ms and error_message attributes needed for RED metrics.

Design doc: OpenTelemetryPlan/ directory in this repo.

Type of Change

• New feature (non-breaking change which adds functionality)
• Tests (you added tests for code that already exists, or your new feature included in this PR)

API Impact

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

Test Plan

• TelemetryConfig_test covers: Setup struct defaults, empty section parsing, fully populated section parsing, and NullTelemetry factory (start/stop no-ops, all should* return false).
• Build with telemetry=ON and verify xrpld links.

Future Tasks

• Phase 3: Transaction tracing with cross-node context propagation
• Phase 4: Consensus round tracing

[codecov]

Codecov Report

❌ Patch coverage is 52.77778% with 17 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (pratik/otel-phase1c-rpc-integration@b5fb71c). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/libxrpl/nodestore/DatabaseNodeImp.cpp	14.3%	6 Missing ⚠️
src/libxrpl/nodestore/backend/RocksDBFactory.cpp	62.5%	3 Missing ⚠️
src/libxrpl/nodestore/backend/MemoryFactory.cpp	50.0%	2 Missing ⚠️
src/libxrpl/nodestore/backend/NuDBFactory.cpp	60.0%	2 Missing ⚠️
src/libxrpl/nodestore/backend/NullFactory.cpp	0.0%	2 Missing ⚠️
src/libxrpl/telemetry/Telemetry.cpp	50.0%	2 Missing ⚠️

Additional details and impacted files

@@                          Coverage Diff                          @@
##             pratik/otel-phase1c-rpc-integration   #6424   +/-   ##
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  Coverage                                       ?   79.8%           
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  Files                                          ?     850           
  Lines                                          ?   67903           
  Branches                                       ?    7578           
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  Hits                                           ?   54154           
  Misses                                         ?   13749           
  Partials                                       ?       0           

Files with missing lines	Coverage Δ
include/xrpl/nodestore/Backend.h	14.3% <ø> (ø)
include/xrpl/telemetry/Telemetry.h	100.0% <ø> (ø)
src/libxrpl/nodestore/DatabaseRotatingImp.cpp	63.9% <100.0%> (ø)
src/libxrpl/telemetry/TelemetryConfig.cpp	100.0% <100.0%> (ø)
src/xrpld/rpc/detail/RPCHandler.cpp	92.4% <100.0%> (ø)
src/libxrpl/nodestore/backend/MemoryFactory.cpp	68.1% <50.0%> (ø)
src/libxrpl/nodestore/backend/NuDBFactory.cpp	64.1% <60.0%> (ø)
src/libxrpl/nodestore/backend/NullFactory.cpp	20.7% <0.0%> (ø)
src/libxrpl/telemetry/Telemetry.cpp	22.5% <50.0%> (ø)
src/libxrpl/nodestore/backend/RocksDBFactory.cpp	49.7% <62.5%> (ø)
... and 1 more

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