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agents,lib,src,test: add traceSampleRate support#430

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santi/tracing_rate
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agents,lib,src,test: add traceSampleRate support#430
santigimeno wants to merge 1 commit intonode-v24.x-nsolid-v6.xfrom
santi/tracing_rate

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@santigimeno santigimeno commented Mar 3, 2026

Add end-to-end traceSampleRate handling across config, runtime propagation, tracing decisions, and regression tests.

Why:

  • Enable configurable probabilistic trace sampling with predictable behavior.
  • Ensure consistent semantics across all config entry points.
  • Prevent invalid updates from corrupting current sampling behavior.
  • Keep transaction consistency by deciding sampling at the root span only.

What changed:

  • Added traceSampleRate parsing and normalization in JS config paths with explicit default fallback and finite/range validation in [0, 1].
  • Added native config sanitization for traceSampleRate to reject invalid values before merge, preserving previous valid configuration.
  • Ensured runtime sampling state is synchronized from effective current config after updates to avoid stale shared-memory sample rates.
  • Added gRPC reconfigure support for traceSampleRate in proto and agent mapping, including generated protobuf updates.
  • Updated tracing logic so root spans perform the sampling decision and child spans inherit parent traceFlags.
  • Extended tests for:
    • invalid value handling (including NaN/Infinity)
    • env/package bootstrap behavior
    • partial updates preserving existing traceSampleRate
    • gRPC invalid-update fallback behavior
    • sampling behavior at 0%, 50% (tolerance), and 100%
    • worker-thread sampling behavior
    • explicit parent/child trace consistency assertions

Summary by CodeRabbit

  • New Features

    • Probabilistic trace sampling for root spans, configurable via env, package.json, or runtime API; value exposed to JS and observable at runtime.
    • Runtime reconfiguration now preserves and propagates trace sampling rate when provided.
  • Bug Fixes

    • Invalid or out-of-range sampling values are rejected and do not overwrite a prior valid rate.
  • Tests

    • Added tests and fixtures validating sampling config precedence, validation, persistence, and sampling behavior.

@santigimeno santigimeno requested a review from RafaelGSS March 3, 2026 16:01
@santigimeno santigimeno self-assigned this Mar 3, 2026
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coderabbitai bot commented Mar 3, 2026

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info
⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b1cd2b91-d009-4f71-b1dc-616255820e41

📥 Commits

Reviewing files that changed from the base of the PR and between 5048dab and 85d36e4.

📒 Files selected for processing (15)
  • agents/grpc/proto/reconfigure.proto
  • agents/grpc/src/grpc_agent.cc
  • agents/grpc/src/proto/reconfigure.pb.cc
  • agents/grpc/src/proto/reconfigure.pb.h
  • lib/internal/otel/trace.js
  • lib/nsolid.js
  • src/nsolid/nsolid_api.cc
  • src/nsolid/nsolid_api.h
  • test/addons/nsolid-tracing/test-otel-basic2.js
  • test/agents/test-grpc-reconfigure.mjs
  • test/fixtures/nsolid-trace-sample-rate-package.json
  • test/fixtures/test-nsolid-config-trace-sample-rate-env-script.js
  • test/parallel/test-nsolid-config-trace-sample-rate-env.js
  • test/parallel/test-nsolid-config-trace-sample-rate.js
  • test/parallel/test-nsolid-trace-sample-rate-sampling.js
🚧 Files skipped from review as they are similar to previous changes (6)
  • lib/internal/otel/trace.js
  • test/agents/test-grpc-reconfigure.mjs
  • test/parallel/test-nsolid-trace-sample-rate-sampling.js
  • test/parallel/test-nsolid-config-trace-sample-rate.js
  • lib/nsolid.js
  • agents/grpc/src/grpc_agent.cc

Walkthrough

Adds a new traceSampleRate config (double, 0–1) propagated through protobufs, gRPC reconfigure, runtime environment APIs, and JS tracing; implements validation, runtime propagation to per-env bindings, probabilistic root-span sampling, and accompanying tests and fixtures.

Changes

Cohort / File(s) Summary
Proto schema & generated code
agents/grpc/proto/reconfigure.proto, agents/grpc/src/proto/reconfigure.pb.h, agents/grpc/src/proto/reconfigure.pb.cc
Added optional traceSampleRate (double, field 14) to ReconfigureBody. Updated generated C++: accessors, has-bit tracking, serialization/deserialization, size/merge/clear logic and parse-table.
gRPC agent logic
agents/grpc/src/grpc_agent.cc
Read traceSampleRate from incoming reconfigure body and include it in outgoing reconfigure payload when present.
JS tracing & config
lib/internal/otel/trace.js, lib/nsolid.js
Root-span sampling switched to probabilistic decision using binding.trace_sample_rate; added DEFAULT_TRACING_SAMPLING_RATE and parseTraceSampleRate() with validation and normalization; config handling updated to accept traceSampleRate.
Runtime C++ API & propagation
src/nsolid/nsolid_api.h, src/nsolid/nsolid_api.cc
Added per-env trace_sample_rate_ and EnvList atomic trace_sample_rate_; validation helpers (validate_trace_sample_rate, validate_config), update_tracing_sample_rate to propagate rate to EnvInsts, and exposed JS ArrayBuffer (trace_sample_rate) for binding.
Tests & fixtures
test/fixtures/nsolid-trace-sample-rate-package.json, test/fixtures/test-nsolid-config-trace-sample-rate-env-script.js, test/addons/nsolid-tracing/test-otel-basic2.js, test/agents/test-grpc-reconfigure.mjs, test/parallel/test-nsolid-config-trace-sample-rate.js, test/parallel/test-nsolid-config-trace-sample-rate-env.js, test/parallel/test-nsolid-trace-sample-rate-sampling.js
Added fixtures and tests for env/package precedence, validation (reject out-of-range/non-finite), reconfigure propagation, child span flag inheritance, and sampling behavior (including worker-thread sampling counts).

Sequence Diagram

sequenceDiagram
    participant App as JavaScript App
    participant Config as nsolid.config
    participant gRPC as gRPC Agent
    participant EnvList as EnvList (C++)
    participant Binding as binding (trace_sample_rate)
    participant Tracer as OpenTelemetry Tracer
    participant Span as Root Span

    App->>Config: updateConfig({traceSampleRate: X})
    Config->>Config: parseTraceSampleRate(X)
    Config->>gRPC: send reconfigure (traceSampleRate: X)
    gRPC->>EnvList: receive reconfigure
    EnvList->>EnvList: validate_trace_sample_rate -> sanitize
    EnvList->>EnvList: update_tracing_sample_rate(X)
    EnvList->>Binding: write trace_sample_rate (shared buffer)

    App->>Tracer: start root span
    Tracer->>Binding: read trace_sample_rate
    Tracer->>Span: decide sample = Math.random() < trace_sample_rate
    alt sampled
        Span->>Span: set flags = SAMPLED
    else not sampled
        Span->>Span: set flags = NONE
    end
    Span-->>Tracer: return span
Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~30 minutes

Suggested reviewers

  • RafaelGSS
  • EHortua

Poem

🐰 I hopped through configs, small and great,

A rate from zero up to one I ate.
Roots decide with a roll and a stare,
Children inherit the flags they share.
Validated, propagated—traces bounce with flair!

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 4.65% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (2 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title 'agents,lib,src,test: add traceSampleRate support' accurately and concisely describes the main change—adding traceSampleRate support across multiple components.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

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  • 📝 Generate docstrings (commit on current branch)
🧪 Generate unit tests (beta)
  • Create PR with unit tests
  • Post copyable unit tests in a comment
  • Commit unit tests in branch santi/tracing_rate

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Actionable comments posted: 3

🧹 Nitpick comments (1)
test/agents/test-grpc-reconfigure.mjs (1)

171-208: Consider adding NaN/Infinity invalid-rate cases in this gRPC path test.

This block currently checks only out-of-range finite numbers. Extending it with Number.NaN and ±Infinity would better guard the gRPC reconfigure edge cases already covered in non-gRPC tests.

✅ Minimal test extension
-        const invalidRates = [2, -0.5];
+        const invalidRates = [2, -0.5, Number.NaN, Number.POSITIVE_INFINITY, Number.NEGATIVE_INFINITY];
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In `@test/agents/test-grpc-reconfigure.mjs` around lines 171 - 208, Update the
test "should preserve previous traceSampleRate for invalid values" to include
NaN and Infinity cases: add Number.NaN, Number.POSITIVE_INFINITY and
Number.NEGATIVE_INFINITY (or +/-Infinity) to the invalidRates array used with
grpcServer.reconfigure and client.config assertions so
grpcServer.reconfigure(agentId, { traceSampleRate: invalidRate }) is exercised
for NaN/Infinity and the existing assert.strictEqual checks that
nsolidConfig.traceSampleRate remained 0.4 still apply.
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@agents/grpc/src/grpc_agent.cc`:
- Around line 1761-1763: PopulateReconfigureEvent currently omits the
traceSampleRate field when building the outgoing reconfigure event body; update
PopulateReconfigureEvent to set body.traceSampleRate from the internal config so
the outgoing event mirrors inbound updates (i.e., when you previously read
body.tracesamplerate() on incoming updates, ensure PopulateReconfigureEvent
calls the corresponding setter to populate body.traceSampleRate in the event).
Locate the PopulateReconfigureEvent function in grpc_agent.cc and add the
traceSampleRate assignment using the same source/field used for other mapped
settings so reconfigure responses include traceSampleRate.

In `@lib/nsolid.js`:
- Around line 1144-1154: The parseTraceSampleRate function currently coerces
unintended types via unary +; update parseTraceSampleRate to only accept inputs
that are typeof 'number' or 'string', explicitly reject booleans and other
types, trim string inputs and return undefined for empty/whitespace-only
strings, then convert the trimmed numeric string (or the number input) to a
numeric value and validate with NumberIsFinite and range checks (>=0 && <=1);
ensure the function returns undefined for invalid types, whitespace-only
strings, NaN, non-finite numbers, or values outside the 0–1 range while
returning the numeric rate for valid inputs.

In `@test/parallel/test-nsolid-config-trace-sample-rate-env.js`:
- Around line 15-18: The test currently spreads process.env into the child env
(env: {...process.env, ...envVars}), which can leak ambient NSOLID_* variables
and make the test nondeterministic; update the env construction in
test/parallel/test-nsolid-config-trace-sample-rate-env.js to explicitly filter
out any keys starting with "NSOLID_" (e.g., build a filteredEnv =
Object.fromEntries(Object.entries(process.env).filter(([k]) =>
!k.startsWith('NSOLID_'))) and then use env: { ...filteredEnv, ...envVars } so
the child process is isolated from ambient NSOLID_* variables while still
allowing envVars to override.

---

Nitpick comments:
In `@test/agents/test-grpc-reconfigure.mjs`:
- Around line 171-208: Update the test "should preserve previous traceSampleRate
for invalid values" to include NaN and Infinity cases: add Number.NaN,
Number.POSITIVE_INFINITY and Number.NEGATIVE_INFINITY (or +/-Infinity) to the
invalidRates array used with grpcServer.reconfigure and client.config assertions
so grpcServer.reconfigure(agentId, { traceSampleRate: invalidRate }) is
exercised for NaN/Infinity and the existing assert.strictEqual checks that
nsolidConfig.traceSampleRate remained 0.4 still apply.

ℹ️ Review info

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 369ce34 and 5048dab.

📒 Files selected for processing (15)
  • agents/grpc/proto/reconfigure.proto
  • agents/grpc/src/grpc_agent.cc
  • agents/grpc/src/proto/reconfigure.pb.cc
  • agents/grpc/src/proto/reconfigure.pb.h
  • lib/internal/otel/trace.js
  • lib/nsolid.js
  • src/nsolid/nsolid_api.cc
  • src/nsolid/nsolid_api.h
  • test/addons/nsolid-tracing/test-otel-basic2.js
  • test/agents/test-grpc-reconfigure.mjs
  • test/fixtures/nsolid-trace-sample-rate-package.json
  • test/fixtures/test-nsolid-config-trace-sample-rate-env-script.js
  • test/parallel/test-nsolid-config-trace-sample-rate-env.js
  • test/parallel/test-nsolid-config-trace-sample-rate.js
  • test/parallel/test-nsolid-trace-sample-rate-sampling.js

RafaelGSS
RafaelGSS previously approved these changes Mar 3, 2026
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RSLGTM

Add end-to-end traceSampleRate handling across config, runtime
propagation, tracing decisions, and regression tests.

Why:
- Enable configurable probabilistic trace sampling with predictable
  behavior.
- Ensure consistent semantics across all config entry points.
- Prevent invalid updates from corrupting current sampling behavior.
- Keep transaction consistency by deciding sampling at the root span
  only.

What changed:
- Added traceSampleRate parsing and normalization in JS config paths
  with explicit default fallback and finite/range validation in [0, 1].
- Added native config sanitization for traceSampleRate to reject invalid
  values before merge, preserving previous valid configuration.
- Ensured runtime sampling state is synchronized from effective current
  config after updates to avoid stale shared-memory sample rates.
- Added gRPC reconfigure support for traceSampleRate in proto and agent
  mapping, including generated protobuf updates.
- Updated tracing logic so root spans perform the sampling decision and
  child spans inherit parent traceFlags.
- Extended tests for:
  - invalid value handling (including NaN/Infinity)
  - env/package bootstrap behavior
  - partial updates preserving existing traceSampleRate
  - gRPC invalid-update fallback behavior
  - sampling behavior at 0%, 50% (tolerance), and 100%
  - worker-thread sampling behavior
  - explicit parent/child trace consistency assertions
@santigimeno santigimeno requested review from EHortua and RafaelGSS March 9, 2026 09:04
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2 participants