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set "supportability.atm_sampling_ratio" and "sampling.threshold" span… #15

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Merged
samohte merged 2 commits into from
Feb 12, 2024
Merged

set "supportability.atm_sampling_ratio" and "sampling.threshold" span… #15

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set "supportability.atm_sampling_ratio" and "sampling.threshold" span…
samohte Feb 7, 2024
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samohte Feb 12, 2024
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29 changes: 23 additions & 6 deletions source/extensions/tracers/opentelemetry/samplers/dynatrace/dynatrace_sampler.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,6 @@ namespace OpenTelemetry {
namespace {

constexpr std::chrono::minutes SAMPLING_UPDATE_TIMER_DURATION{1};
const char* SAMPLING_EXTRAPOLATION_SPAN_ATTRIBUTE_NAME = "sampling_extrapolation_set_in_sampler";

class DynatraceTag {
public:
Expand Down Expand Up @@ -73,6 +72,26 @@ class DynatraceTag {
uint32_t path_info_;
};

// add Dynatrace specific span attributes
void addSamplingAttributes(uint32_t sampling_exponent,
std::map<std::string, std::string>& attributes) {

const auto multiplicity = SamplingState::toMultiplicity(sampling_exponent);
// The denominator of the sampling ratio. If, for example, the Dynatrace OneAgent samples with a
// probability of 1/16, the value of supportability.atm_sampling_ratio would be 16.
// Note: Ratio is also known as multiplicity.
attributes["supportability.atm_sampling_ratio"] = std::to_string(multiplicity);

if (multiplicity > 1) {
static constexpr uint64_t two_pow_56 = 1lu << 56; // 2^56
// The sampling probability can be interpreted as the number of spans
// that are discarded out of 2^56. The attribute is only available if the sampling.threshold is
// not 0 and therefore sampling happened.
const uint64_t sampling_threshold = two_pow_56 - two_pow_56 / multiplicity;
attributes["sampling.threshold"] = std::to_string(sampling_threshold);
}
}

} // namespace

DynatraceSampler::DynatraceSampler(
Expand Down Expand Up @@ -118,9 +137,7 @@ SamplingResult DynatraceSampler::shouldSample(const absl::optional<SpanContext>
if (DynatraceTag dynatrace_tag = DynatraceTag::create(trace_state_value);
dynatrace_tag.isValid()) {
result.decision = dynatrace_tag.isIgnored() ? Decision::Drop : Decision::RecordAndSample;
// TODO: change attribute name and value in scope of OA-26680
att[SAMPLING_EXTRAPOLATION_SPAN_ATTRIBUTE_NAME] =
std::to_string(dynatrace_tag.getSamplingExponent());
addSamplingAttributes(dynatrace_tag.getSamplingExponent(), att);
result.tracestate = parent_context->tracestate();
}
} else {
Expand All @@ -130,8 +147,8 @@ SamplingResult DynatraceSampler::shouldSample(const absl::optional<SpanContext>
const auto sampling_state = sampling_controller_.getSamplingState(sampling_key);
const bool sample = sampling_state.shouldSample(hash);
const auto sampling_exponent = sampling_state.getExponent();
// TODO: change attribute name and value in scope of OA-26680
att[SAMPLING_EXTRAPOLATION_SPAN_ATTRIBUTE_NAME] = std::to_string(sampling_exponent);

addSamplingAttributes(sampling_exponent, att);

result.decision = sample ? Decision::RecordAndSample : Decision::Drop;
// create new forward tag and add it to tracestate
Expand Down
13 changes: 13 additions & 0 deletions test/extensions/tracers/opentelemetry/samplers/dynatrace/dynatrace_sampler_test.cc
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Expand Up @@ -80,6 +80,8 @@ TEST_F(DynatraceSamplerTest, TestWithoutParentContext) {
::opentelemetry::proto::trace::v1::Span::SPAN_KIND_SERVER, {}, {});
EXPECT_EQ(sampling_result.decision, Decision::RecordAndSample);
EXPECT_EQ(sampling_result.attributes->size(), 1);
EXPECT_STREQ(
sampling_result.attributes->find("supportability.atm_sampling_ratio")->second.c_str(), "1");
EXPECT_STREQ(sampling_result.tracestate.c_str(), "5b3f9fed-980df25c@dt=fw4;0;0;0;0;0;0;95");
EXPECT_TRUE(sampling_result.isRecording());
EXPECT_TRUE(sampling_result.isSampled());
Expand All @@ -94,6 +96,8 @@ TEST_F(DynatraceSamplerTest, TestWithUnknownParentContext) {
::opentelemetry::proto::trace::v1::Span::SPAN_KIND_SERVER, {}, {});
EXPECT_EQ(sampling_result.decision, Decision::RecordAndSample);
EXPECT_EQ(sampling_result.attributes->size(), 1);
EXPECT_STREQ(
sampling_result.attributes->find("supportability.atm_sampling_ratio")->second.c_str(), "1");
// Dynatrace tracesate should be prepended
EXPECT_STREQ(sampling_result.tracestate.c_str(),
"5b3f9fed-980df25c@dt=fw4;0;0;0;0;0;0;95,some_vendor=some_value");
Expand All @@ -110,6 +114,8 @@ TEST_F(DynatraceSamplerTest, TestWithDynatraceParentContextSampled) {
::opentelemetry::proto::trace::v1::Span::SPAN_KIND_SERVER, {}, {});
EXPECT_EQ(sampling_result.decision, Decision::RecordAndSample);
EXPECT_EQ(sampling_result.attributes->size(), 1);
EXPECT_STREQ(
sampling_result.attributes->find("supportability.atm_sampling_ratio")->second.c_str(), "1");
// tracestate should be forwarded
EXPECT_STREQ(sampling_result.tracestate.c_str(), dt_tracestate_sampled);
// sampling decision from parent should be respected
Expand All @@ -126,6 +132,11 @@ TEST_F(DynatraceSamplerTest, TestWithDynatraceParentContextIgnored) {
::opentelemetry::proto::trace::v1::Span::SPAN_KIND_SERVER, {}, {});
EXPECT_EQ(sampling_result.decision, Decision::Drop);
EXPECT_EQ(sampling_result.attributes->size(), 1);
EXPECT_EQ(sampling_result.attributes->size(), 2);
EXPECT_STREQ(
sampling_result.attributes->find("supportability.atm_sampling_ratio")->second.c_str(), "4");
EXPECT_STREQ(sampling_result.attributes->find("sampling.threshold")->second.c_str(),
"54043195528445952");
// tracestate should be forwarded
EXPECT_STREQ(sampling_result.tracestate.c_str(), dt_tracestate_ignored);
// sampling decision from parent should be respected
Expand All @@ -144,6 +155,8 @@ TEST_F(DynatraceSamplerTest, TestWithDynatraceParentContextFromDifferentTenant)
// sampling decision on tracestate should be ignored because it is from a different tenant.
EXPECT_EQ(sampling_result.decision, Decision::RecordAndSample);
EXPECT_EQ(sampling_result.attributes->size(), 1);
EXPECT_STREQ(
sampling_result.attributes->find("supportability.atm_sampling_ratio")->second.c_str(), "1");
// new Dynatrace tag should be prepended, already existing tag should be kept
const char* exptected =
"5b3f9fed-980df25c@dt=fw4;0;0;0;0;0;0;95,6666ad40-980df25c@dt=fw4;4;4af38366;0;0;1;2;123;"
Expand Down