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fix(telemetry): use thread_local PRNG for span IDs and update class diagram

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Replace per-call std::random_device with thread_local std::mt19937 in
txSpan() for span ID generation. random_device is ~423x slower due to
/dev/urandom syscalls on each construction; mt19937 is seeded once per
thread and reused for all subsequent span IDs.

Update the SpanGuard class ASCII diagram to include txSpan factory
methods that were added in the hash-derived trace ID commit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Pratik Mankawde
2026-04-27 14:34:47 +01:00
parent f4186165e4
commit 2c9528232d
2 changed files with 21 additions and 19 deletions
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36
include/xrpl/telemetry/SpanGuard.h
View File

@@ -9,23 +9,25 @@
Dependency diagram:
+-------------------------------------------+
| SpanGuard |
+-------------------------------------------+
| - impl_ : unique_ptr<Impl> (pimpl) |
+-------------------------------------------+
| + span(name) : SpanGuard [static] |
| + span(cat, prefix, name) [static] |
| + childSpan(name) : SpanGuard |
| + linkedSpan(name) : SpanGuard |
| + captureContext() : SpanContext |
| + setAttribute(key, value) |
| + setOk() / setError(desc) |
| + addEvent(name) |
| + recordException(e) |
| + discard() |
| + operator bool() |
+-------------------------------------------+
+------------------------------------------------+
| SpanGuard |
+------------------------------------------------+
| - impl_ : unique_ptr<Impl> (pimpl) |
+------------------------------------------------+
| + span(name) : SpanGuard [static] |
| + span(cat, prefix, name) [static] |
| + childSpan(name) : SpanGuard |
| + linkedSpan(name) : SpanGuard |
| + txSpan(prefix, name, hash) [static] |
| + txSpan(prefix, name, hash, parent) [static] |
| + captureContext() : SpanContext |
| + setAttribute(key, value) |
| + setOk() / setError(desc) |
| + addEvent(name) |
| + recordException(e) |
| + discard() |
| + operator bool() |
+------------------------------------------------+
| hides (pimpl)
+-------+-------+
| |

4
src/libxrpl/telemetry/SpanGuard.cpp
View File

@@ -258,9 +258,9 @@ SpanGuard::txSpan(
otel_trace::TraceId traceId(opentelemetry::nostd::span<std::uint8_t const, 16>(hashData, 16));
std::uint8_t spanIdBytes[8];
std::random_device rd;
thread_local std::mt19937 prng{std::random_device{}()};
for (auto& b : spanIdBytes)
b = static_cast<std::uint8_t>(rd());
b = static_cast<std::uint8_t>(prng());
otel_trace::SpanId spanId(opentelemetry::nostd::span<std::uint8_t const, 8>(spanIdBytes, 8));
otel_trace::SpanContext syntheticCtx(