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fix(telemetry): hashSpan standalone spans are true roots via DeterministicIdGenerator

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The single-arg hashSpan fabricated a synthetic DefaultSpan parent (random
span_id) to carry the deterministic trace_id. That left every standalone
hash span with a phantom parent_span_id pointing at a span that is never
exported, so Tempo reported "root span not yet received".

Inject the deterministic trace_id through the DeterministicIdGenerator
instead: start the span on the SDK root branch (Context{kIsRootSpanKey,true})
with a PendingTraceId pinning hashData[0:16]. The SDK's no-valid-parent
branch calls GenerateTraceId(), which returns the pinned id, yielding a
TRUE root (empty parent_span_id) whose trace_id == hashData[0:16].

The deterministic bytes are unchanged (still raw hashData[0:16]). The
cross-node overload (real remote parent, remote=true) is untouched and must
keep producing a child of the sender's span. Drop the now-unused
<xrpl/basics/random.h> include; add <array> and DeterministicIdGenerator.h.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Pratik Mankawde
2026-07-21 20:10:10 +01:00
parent 14d3d5baa3
commit d63d5bd45e
1 changed files with 17 additions and 19 deletions
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36
src/libxrpl/telemetry/SpanGuard.cpp
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@@ -28,8 +28,8 @@
#include <xrpl/telemetry/SpanGuard.h>
#include <xrpl/basics/random.h>
#include <xrpl/beast/utility/instrumentation.h>
#include <xrpl/telemetry/DeterministicIdGenerator.h>
#include <xrpl/telemetry/DiscardFlag.h>
#include <xrpl/telemetry/Telemetry.h>
@@ -49,6 +49,7 @@
#include <opentelemetry/trace/trace_flags.h>
#include <opentelemetry/trace/trace_id.h>
#include <array>
#include <cstdint>
#include <cstring>
#include <exception>
@@ -303,6 +304,7 @@ SpanGuard::linkedSpan(std::string_view name, SpanContext const& linkCtx)
// ===== Hash-derived span (category-gated) ==================================
// Standalone hash-derived span: a TRUE root whose trace_id == hashData[0:16].
SpanGuard
SpanGuard::hashSpan(
TraceCategory const cat,
@@ -316,26 +318,22 @@ SpanGuard::hashSpan(
if ((tel == nullptr) || !tel->isEnabled() || !isCategoryEnabled(*tel, cat))
return {};
otel_trace::TraceId const traceId(
opentelemetry::nostd::span<std::uint8_t const, 16>(hashData, 16));
auto const rval = defaultPrng()();
std::uint8_t spanIdBytes[8];
std::memcpy(spanIdBytes, &rval, sizeof(spanIdBytes));
otel_trace::SpanId const spanId(
opentelemetry::nostd::span<std::uint8_t const, 8>(spanIdBytes, 8));
otel_trace::SpanContext const syntheticCtx(
traceId, spanId, otel_trace::TraceFlags(1), /* remote = */ false);
auto parentCtx = opentelemetry::context::Context{}.SetValue(
otel_trace::kSpanKey,
opentelemetry::nostd::shared_ptr<otel_trace::Span>(
new otel_trace::DefaultSpan(syntheticCtx)));
return SpanGuard(std::make_unique<Impl>(tel->startSpan(std::string(name), parentCtx)));
// Force the deterministic trace_id via the DeterministicIdGenerator, on the
// SDK root branch, so the span is a TRUE root (empty parent_span_id) whose
// trace_id == hashData[0:16]. The kIsRootSpanKey context forces the SDK's
// no-valid-parent branch, where GenerateTraceId() is called and returns the
// pending id. The PendingTraceId guard scopes that id to this one startSpan.
std::array<std::uint8_t, 16> tid{};
std::memcpy(tid.data(), hashData, 16);
auto rootCtx = opentelemetry::context::Context{otel_trace::kIsRootSpanKey, true};
PendingTraceId const pending{tid};
return SpanGuard(
std::make_unique<Impl>(
tel->startSpan(std::string(name), rootCtx, categoryToSpanKind(cat))));
}
// Cross-node hash-derived span: a CHILD of the sender's real remote span
// (remote=true), not a root — so it must NOT use PendingTraceId / rootCtx.
SpanGuard
SpanGuard::hashSpan(
TraceCategory const cat,