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[SDK] Ensure TraceId is portable on big-endian architectures #3543

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Merged
merged 3 commits into from
Jul 16, 2025
+9 −4
Merged

[SDK] Ensure TraceId is portable on big-endian architectures #3543

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9377a5d
[SDK] Ensure TraceId is portable on big-endian architectures
strophy Jul 16, 2025
4ba7cad
Merge branch 'main' into s390x-endianness-traceid-fix
marcalff Jul 16, 2025
6c02f81
Update trace_id_ratio.cc
marcalff Jul 16, 2025
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11 changes: 8 additions & 3 deletions sdk/src/trace/samplers/trace_id_ratio.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -4,11 +4,11 @@

#include <cmath>
#include <cstdint>
#include <cstring>
#include <map>
#include <memory>
#include <string>

#include "opentelemetry/nostd/span.h"
#include "opentelemetry/nostd/string_view.h"
#include "opentelemetry/sdk/trace/sampler.h"
#include "opentelemetry/sdk/trace/samplers/trace_id_ratio.h"
Expand Down Expand Up @@ -56,8 +56,13 @@ uint64_t CalculateThresholdFromBuffer(const trace_api::TraceId &trace_id) noexce
// We only use the first 8 bytes of TraceId.
static_assert(trace_api::TraceId::kSize >= 8, "TraceID must be at least 8 bytes long.");

uint64_t res = 0;
std::memcpy(&res, &trace_id, 8);
// Always interpret as big-endian
const uint8_t *data = trace_id.Id().data();
uint64_t res = 0;
for (int i = 0; i < 8; ++i)
{
res = (res << 8) | data[i];
}

double ratio = static_cast<double>(res) / static_cast<double>(UINT64_MAX);

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2 changes: 1 addition & 1 deletion sdk/test/trace/trace_id_ratio_sampler_test.cc
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Expand Up @@ -99,7 +99,7 @@ TEST(TraceIdRatioBasedSampler, ShouldSampleWithoutContext)
ASSERT_EQ(Decision::RECORD_AND_SAMPLE, sampling_result.decision);
ASSERT_EQ(nullptr, sampling_result.attributes);

constexpr uint8_t buf[] = {0, 0, 0, 0, 0, 0, 0, 0x80, 0, 0, 0, 0, 0, 0, 0, 0};
constexpr uint8_t buf[] = {0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
trace_api::TraceId valid_trace_id(buf);

sampling_result = s1.ShouldSample(trace_api::SpanContext::GetInvalid(), valid_trace_id, "",
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