Fix otlp generates null span ids (#1113)

Author: esigo

CHANGELOG.md

@@ -15,6 +15,8 @@ Increment the:
 
 ## [Unreleased]
 
+* [EXPORTER] Fix otlp generates null span ids ([#1106](https://github.com/open-telemetry/opentelemetry-cpp/pull/1106))
+
 ## [1.1.0] 2021-11-19
 
 * [BUILD] build release tarball when nlohmann-json not installed ([#1074](https://github.com/open-telemetry/opentelemetry-cpp/pull/1074))

exporters/otlp/src/otlp_recordable.cc

@@ -20,8 +20,11 @@ void OtlpRecordable::SetIdentity(const opentelemetry::trace::SpanContext &span_c
                      trace::TraceId::kSize);
   span_.set_span_id(reinterpret_cast<const char *>(span_context.span_id().Id().data()),
                     trace::SpanId::kSize);
-  span_.set_parent_span_id(reinterpret_cast<const char *>(parent_span_id.Id().data()),
-                           trace::SpanId::kSize);
+  if (parent_span_id.IsValid())
+  {
+    span_.set_parent_span_id(reinterpret_cast<const char *>(parent_span_id.Id().data()),
+                             trace::SpanId::kSize);
+  }
   span_.set_trace_state(span_context.trace_state()->ToHeader());
 }
 

exporters/otlp/test/otlp_recordable_test.cc

@@ -39,6 +39,14 @@ TEST(OtlpRecordable, SetIdentity)
   EXPECT_EQ(rec.span().parent_span_id(),
             std::string(reinterpret_cast<const char *>(parent_span_id.Id().data()),
                         trace::SpanId::kSize));
+
+  OtlpRecordable rec_invalid_parent;
+
+  constexpr uint8_t invalid_parent_span_id_buf[] = {0, 0, 0, 0, 0, 0, 0, 0};
+  trace_api::SpanId invalid_parent_span_id{invalid_parent_span_id_buf};
+  rec_invalid_parent.SetIdentity(span_context, invalid_parent_span_id);
+
+  EXPECT_EQ(rec_invalid_parent.span().parent_span_id(), std::string{});
 }
 
 TEST(OtlpRecordable, SetName)