Propagate trace and parent span ids

sdk/src/trace/span.cc

@@ -2,6 +2,7 @@
 #include "src/common/random.h"
 
 #include "opentelemetry/context/runtime_context.h"
+#include "opentelemetry/trace/trace_flags.h"
 #include "opentelemetry/version.h"
 
 OPENTELEMETRY_BEGIN_NAMESPACE
@@ -77,16 +78,22 @@ Span::Span(std::shared_ptr<Tracer> &&tracer,
   }
   recordable_->SetName(name);
 
+  trace_api::TraceId trace_id;
+  trace_api::SpanId span_id = GenerateRandomSpanId();
+
   if (parent_span_context.IsValid())
   {
-    recordable_->SetIds(parent_span_context.trace_id(), GenerateRandomSpanId(),
-                        parent_span_context.span_id());
+    trace_id = parent_span_context.trace_id();
+    recordable_->SetIds(trace_id, span_id, parent_span_context.span_id());
   }
   else
   {
-    recordable_->SetIds(GenerateRandomTraceId(), GenerateRandomSpanId(), trace_api::SpanId());
+    trace_id = GenerateRandomTraceId();
+    recordable_->SetIds(trace_id, span_id, trace_api::SpanId());
   }
-  // TODO: Create and populate SpanContext for this span when SpanContext is fully implemented
+
+  span_context_ = std::unique_ptr<trace_api::SpanContext>(
+      new trace_api::SpanContext(trace_id, span_id, trace_api::TraceFlags(), false));
 
   attributes.ForEachKeyValue([&](nostd::string_view key,
                                  opentelemetry::common::AttributeValue value) noexcept {

sdk/src/trace/tracer.cc

@@ -30,6 +30,20 @@ std::shared_ptr<Sampler> Tracer::GetSampler() const noexcept
   return sampler_;
 }
 
+// Helper function to extract the current span context from the runtime context.
+// Returns an invalid span context if the runtime context doesn't contain a span.
+trace_api::SpanContext GetCurrentSpanContext()
+{
+  context::ContextValue curr_span_context = context::RuntimeContext::GetValue(SpanKey);
+
+  if (nostd::holds_alternative<nostd::shared_ptr<trace_api::Span>>(curr_span_context))
+  {
+    auto curr_span = nostd::get<nostd::shared_ptr<trace_api::Span>>(curr_span_context);
+    return curr_span->GetContext();
+  }
+  return trace_api::SpanContext();
+}
+
 nostd::shared_ptr<trace_api::Span> Tracer::StartSpan(
     nostd::string_view name,
     const trace_api::KeyValueIterable &attributes,
@@ -47,13 +61,9 @@ nostd::shared_ptr<trace_api::Span> Tracer::StartSpan(
   }
   else
   {
-    // TODO: Get parent span context from current context. For now we assume all spans
-    // have no parent, and pass an invalid parent span context to the Span constructor.
-    const trace_api::SpanContext kInvalidParentSpanContext(false, false);
-
     auto span = nostd::shared_ptr<trace_api::Span>{
         new (std::nothrow) Span{this->shared_from_this(), processor_.load(), name, attributes,
-                                options, kInvalidParentSpanContext}};
+                                options, GetCurrentSpanContext()}};
 
     span->SetToken(
         nostd::unique_ptr<context::Token>(new context::Token(context::RuntimeContext::Attach(

sdk/test/trace/tracer_test.cc

@@ -113,11 +113,16 @@ TEST(Tracer, ToMockSpanExporter)
   ASSERT_EQ("span 2", spans_received->at(0)->GetName());
   EXPECT_TRUE(spans_received->at(0)->GetTraceId().IsValid());
   EXPECT_TRUE(spans_received->at(0)->GetSpanId().IsValid());
-  EXPECT_FALSE(spans_received->at(0)->GetParentSpanId().IsValid());
+  EXPECT_TRUE(spans_received->at(0)->GetParentSpanId().IsValid());
 
   span_first->End();
   ASSERT_EQ(2, spans_received->size());
 
+  // Verify trace and parent span id propagation
+  EXPECT_EQ(span_second->GetContext().trace_id(), span_first->GetContext().trace_id());
+  EXPECT_EQ(spans_received->at(0)->GetTraceId(), spans_received->at(1)->GetTraceId());
+  EXPECT_EQ(spans_received->at(0)->GetParentSpanId(), spans_received->at(1)->GetSpanId());
+
   ASSERT_EQ("span 1", spans_received->at(1)->GetName());
   EXPECT_TRUE(spans_received->at(1)->GetTraceId().IsValid());
   EXPECT_TRUE(spans_received->at(1)->GetSpanId().IsValid());