[ETW Exporter] Tail based sampling support (open-telemetry#1780)

exporters/etw/include/opentelemetry/exporters/etw/etw_config.h

@@ -12,6 +12,7 @@
 
 #include "opentelemetry//sdk/trace/sampler.h"
 #include "opentelemetry/exporters/etw/etw_provider.h"
+#include "opentelemetry/exporters/etw/etw_tail_sampler.h"
 #include "opentelemetry/sdk/trace/id_generator.h"
 
 OPENTELEMETRY_BEGIN_NAMESPACE
@@ -166,6 +167,15 @@ sdk::trace::Sampler &GetSampler(T &t)
  return *t.sampler_;
 }
 
+/**
+ * @brief Utility function to obtain etw::TracerProvider.tail_sampler_
+ */
+template <class T>
+TailSampler &GetTailSampler(T &t)
+{
+ return *t.tail_sampler_;
+}
+
 /**
  * @brief Utility template to convert SpanId or TraceId to hex.
  * @param id - value of SpanId or TraceId

exporters/etw/include/opentelemetry/exporters/etw/etw_tail_sampler.h

@@ -0,0 +1,38 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+#include "opentelemetry/sdk/trace/sampler.h"
+#include "opentelemetry/trace/span.h"
+
+#pragma once
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace etw
+{
+
+class TailSampler
+{
+public:
+ // convert to etw span if required for getters on span.
+ // auto etw_span = static_cast<const opentelemetry::exporter::etw::Span*>(&span);
+ // Decision based on
+ // Span::GetStatus()
+ // Span::GetProperties()
+ // Span::GetContext()
+ virtual opentelemetry::sdk::trace::SamplingResult ShouldSample(
+ const opentelemetry::trace::Span &span) noexcept = 0;
+};
+
+class AlwaysOnTailSampler : public TailSampler
+{
+public:
+ opentelemetry::sdk::trace::SamplingResult ShouldSample(
+ const opentelemetry::trace::Span &span) noexcept override
+ {
+ return {opentelemetry::sdk::trace::Decision::RECORD_AND_SAMPLE};
+ }
+};
+
+} // namespace etw
+} // namespace exporter
+OPENTELEMETRY_END_NAMESPACE

exporters/etw/include/opentelemetry/exporters/etw/etw_tracer.h

@@ -40,6 +40,7 @@
 #include "opentelemetry/exporters/etw/etw_properties.h"
 #include "opentelemetry/exporters/etw/etw_provider.h"
 #include "opentelemetry/exporters/etw/etw_random_id_generator.h"
+#include "opentelemetry/exporters/etw/etw_tail_sampler.h"
 #include "opentelemetry/exporters/etw/utils.h"
 
 OPENTELEMETRY_BEGIN_NAMESPACE
@@ -235,9 +236,17 @@ class Tracer : public opentelemetry::trace::Tracer,
  const opentelemetry::trace::Span *parentSpan = nullptr,
  const opentelemetry::trace::EndSpanOptions & = {})
  {
- const auto &cfg = GetConfiguration(tracerProvider_);
+ const auto &cfg = GetConfiguration(tracerProvider_);
+ const auto &tail_sampler = GetTailSampler(tracerProvider_);
  const opentelemetry::trace::Span &spanBase =
  reinterpret_cast<const opentelemetry::trace::Span &>(span);
+
+ // Sample span based on the decision of tail based sampler
+ auto sampling_result = const_cast<TailSampler *>(&tail_sampler)->ShouldSample(spanBase);
+ if (!sampling_result.IsRecording() || !sampling_result.IsSampled())
+ {
+ return;
+ }
  auto spanContext = spanBase.GetContext();
 
  // Populate Span with presaved attributes
@@ -375,17 +384,23 @@ class Tracer : public opentelemetry::trace::Tracer,
  const opentelemetry::trace::SpanContextKeyValueIterable &links,
  const opentelemetry::trace::StartSpanOptions &options = {}) noexcept override
  {
-#ifdef OPENTELEMETRY_RTTI_ENABLED
+ // If RTTI is enabled by compiler, the below code modifies the attributes object passed as arg,
+ // which is sometime not desirable, set OPENTELEMETRY_NOT_USE_RTTI in application
+ // to avoid using RTTI in that case in below set of code.
+#if !defined OPENTELEMETRY_RTTI_ENABLED || defined OPENTELEMETRY_NOT_USE_RTTI
+ Properties evtCopy = attributes;
+ return StartSpan(name, evtCopy, links, options);
+#else // OPENTELEMETRY_RTTI_ENABLED is defined
  common::KeyValueIterable &attribs = const_cast<common::KeyValueIterable &>(attributes);
  Properties *evt = dynamic_cast<Properties *>(&attribs);
  if (evt != nullptr)
  {
  // Pass as a reference to original modifyable collection without creating a copy
  return StartSpan(name, *evt, links, options);
  }
-#endif
  Properties evtCopy = attributes;
  return StartSpan(name, evtCopy, links, options);
+#endif
  }
 
  /**
@@ -557,18 +572,24 @@ class Tracer : public opentelemetry::trace::Tracer,
  common::SystemTimestamp timestamp,
  const common::KeyValueIterable &attributes) noexcept
  {
-#ifdef OPENTELEMETRY_RTTI_ENABLED
+ // If RTTI is enabled by compiler, the below code modifies the attributes object passed as arg,
+ // which is sometime not desirable, set OPENTELEMETRY_NOT_USE_RTTI in application
+ // to avoid using RTTI in that case in below set of code.
+#if !defined OPENTELEMETRY_RTTI_ENABLED || defined OPENTELEMETRY_NOT_USE_RTTI
+ // Pass a copy converted to Properties object on stack
+ Properties evtCopy = attributes;
+ return AddEvent(span, name, timestamp, evtCopy);
+#else // OPENTELEMETRY_RTTI_ENABLED is defined
  common::KeyValueIterable &attribs = const_cast<common::KeyValueIterable &>(attributes);
  Properties *evt = dynamic_cast<Properties *>(&attribs);
  if (evt != nullptr)
  {
  // Pass as a reference to original modifyable collection without creating a copy
  return AddEvent(span, name, timestamp, *evt);
  }
-#endif
- // Pass a copy converted to Properties object on stack
  Properties evtCopy = attributes;
  return AddEvent(span, name, timestamp, evtCopy);
+#endif
  }
 
  /**
@@ -826,6 +847,8 @@ class Span : public opentelemetry::trace::Span
  status_description_ = description.data();
  }
 
+ opentelemetry::trace::StatusCode GetStatus() { return status_code_; }
+
  void SetAttributes(Properties attributes) { attributes_ = attributes; }
 
  /**
@@ -932,6 +955,12 @@ class TracerProvider : public opentelemetry::trace::TracerProvider
  */
  std::unique_ptr<sdk::trace::Sampler> sampler_;
 
+ /**
+ * @brief Sampler configured
+ *
+ */
+ std::unique_ptr<opentelemetry::exporter::etw::TailSampler> tail_sampler_;
+
  /**
  * @brief IdGenerator for trace_id and span_id
  *
@@ -942,15 +971,19 @@ class TracerProvider : public opentelemetry::trace::TracerProvider
  * @brief Construct instance of TracerProvider with given options
  * @param options Configuration options
  */
- TracerProvider(TelemetryProviderOptions options,
- std::unique_ptr<sdk::trace::Sampler> sampler =
- std::unique_ptr<sdk::trace::AlwaysOnSampler>(new sdk::trace::AlwaysOnSampler),
- std::unique_ptr<sdk::trace::IdGenerator> id_generator =
- std::unique_ptr<opentelemetry::sdk::trace::IdGenerator>(
- new sdk::trace::ETWRandomIdGenerator()))
+ TracerProvider(
+ TelemetryProviderOptions options,
+ std::unique_ptr<sdk::trace::Sampler> sampler =
+ std::unique_ptr<sdk::trace::AlwaysOnSampler>(new sdk::trace::AlwaysOnSampler),
+ std::unique_ptr<sdk::trace::IdGenerator> id_generator =
+ std::unique_ptr<opentelemetry::sdk::trace::IdGenerator>(
+ new sdk::trace::ETWRandomIdGenerator()),
+ std::unique_ptr<opentelemetry::exporter::etw::TailSampler> tail_sampler =
+ std::unique_ptr<opentelemetry::exporter::etw::TailSampler>(new AlwaysOnTailSampler()))
  : opentelemetry::trace::TracerProvider(),
  sampler_{std::move(sampler)},
- id_generator_{std::move(id_generator)}
+ id_generator_{std::move(id_generator)},
+ tail_sampler_{std::move(tail_sampler)}
  {
  // By default we ensure that all events carry their with TraceId and SpanId
  GetOption(options, "enableTraceId", config_.enableTraceId, true);
@@ -985,7 +1018,9 @@ class TracerProvider : public opentelemetry::trace::TracerProvider
  : opentelemetry::trace::TracerProvider(),
  sampler_{std::unique_ptr<sdk::trace::AlwaysOnSampler>(new sdk::trace::AlwaysOnSampler)},
  id_generator_{std::unique_ptr<opentelemetry::sdk::trace::IdGenerator>(
- new sdk::trace::ETWRandomIdGenerator())}
+ new sdk::trace::ETWRandomIdGenerator())},
+ tail_sampler_{
+ std::unique_ptr<opentelemetry::exporter::etw::TailSampler>(new AlwaysOnTailSampler())}
  {
  config_.enableTraceId = true;
  config_.enableSpanId = true;

exporters/etw/test/etw_tracer_test.cc

@@ -6,7 +6,6 @@
 # include <gtest/gtest.h>
 # include <map>
 # include <string>
-
 # include "opentelemetry//sdk/trace/sampler.h"
 # include "opentelemetry/exporters/etw/etw_tracer_exporter.h"
 # include "opentelemetry/sdk/trace/samplers/always_off.h"
@@ -78,6 +77,16 @@ class MockSampler : public sdk::trace::Sampler
  std::shared_ptr<Sampler> delegate_sampler_;
 };
 
+class AlwaysOffTailSampler : public TailSampler
+{
+public:
+ opentelemetry::sdk::trace::SamplingResult ShouldSample(
+ const opentelemetry::trace::Span &span) noexcept override
+ {
+ return {opentelemetry::sdk::trace::Decision::DROP};
+ }
+};
+
 /* clang-format off */
 TEST(ETWTracer, TracerCheck)
 {
@@ -459,6 +468,26 @@ TEST(ETWTracer, AlwayOffSampler)
  EXPECT_EQ(span->GetContext().IsSampled(), false);
 }
 
+TEST(ETWTracer, AlwayOffTailSampler)
+{
+ std::string providerName = kGlobalProviderName; // supply unique instrumentation name here
+ std::unique_ptr<sdk::trace::Sampler> always_on{new sdk::trace::AlwaysOnSampler()};
+ sdk::trace::IdGenerator *id_generator = new MockIdGenerator();
+ std::unique_ptr<TailSampler> always_off_tail{new AlwaysOffTailSampler()};
+ exporter::etw::TracerProvider tp
+ ({
+ {"enableTraceId", true},
+ {"enableSpanId", true},
+ {"enableActivityId", true},
+ {"enableRelatedActivityId", true},
+ {"enableAutoParent", true}
+ },
+ std::move(always_on),
+ std::unique_ptr<sdk::trace::IdGenerator>(id_generator),
+ std::move(always_off_tail));
+ auto tracer = tp.GetTracer(providerName);
+}
+
 TEST(ETWTracer, CustomIdGenerator)
 {
  std::string providerName = kGlobalProviderName; // supply unique instrumentation name here