impl(pubsub): start the publish span as a root span

google/cloud/pubsub/internal/tracing_batch_sink.cc

@@ -60,6 +60,13 @@ auto MakeParent(Links const& links, Spans const& message_spans,
  pubsub::Topic const& topic) {
  namespace sc = ::opentelemetry::trace::SemanticConventions;
  opentelemetry::trace::StartSpanOptions options;
+ opentelemetry::context::Context root_context;
+ // TODO(#13287): Use the constant instead of the string.
+ // Setting a span as a root span was added in OTel v1.13+. It is a no-op for
+ // earlier versions.
+ root_context = root_context.SetValue(
+ /*opentelemetry::trace::kIsRootSpanKey=*/"is_root_span", true);
+ options.parent = root_context;
  options.kind = opentelemetry::trace::SpanKind::kClient;
  auto batch_sink_parent = internal::MakeSpan(
  topic.topic_id() + " publish",
@@ -74,7 +81,6 @@ auto MakeParent(Links const& links, Spans const& message_spans,
  {sc::kMessagingDestinationTemplate, topic.FullName()}},
  /*links*/ std::move(links), options);
 
- // Add metadata to the message spans about the batch sink span.
  auto context = batch_sink_parent->GetContext();
  auto trace_id = internal::ToString(context.trace_id());
  auto span_id = internal::ToString(context.span_id());

google/cloud/pubsub/internal/tracing_batch_sink_test.cc

@@ -43,6 +43,7 @@ using ::google::cloud::testing_util::SpanEventAttributesAre;
 using ::google::cloud::testing_util::SpanHasAttributes;
 using ::google::cloud::testing_util::SpanHasEvents;
 using ::google::cloud::testing_util::SpanHasInstrumentationScope;
+using ::google::cloud::testing_util::SpanIsRoot;
 using ::google::cloud::testing_util::SpanKindIsClient;
 using ::google::cloud::testing_util::SpanLinksSizeIs;
 using ::google::cloud::testing_util::SpanNamed;
@@ -216,6 +217,32 @@ TEST(TracingBatchSink, PublishSpanHasAttributes) {
  TestTopic().FullName())))));
 }
 
+#if OPENTELEMETRY_VERSION_MAJOR >= 2 || \
+ (OPENTELEMETRY_VERSION_MAJOR == 1 && OPENTELEMETRY_VERSION_MINOR >= 13)
+TEST(TracingBatchSink, PublishSpanIsRoot) {
+ auto span_catcher = InstallSpanCatcher();
+ auto message_span = MakeSpan("test span");
+ auto scope = opentelemetry::trace::Scope(message_span);
+ auto mock = std::make_unique<pubsub_testing::MockBatchSink>();
+ EXPECT_CALL(*mock, AddMessage(_));
+ EXPECT_CALL(*mock, AsyncPublish)
+ .WillOnce([](google::pubsub::v1::PublishRequest const& request) {
+ EXPECT_THAT(request, IsProtoEqual(MakeRequest(1)));
+ return make_ready_future(make_status_or(MakeResponse(request)));
+ });
+ auto batch_sink = MakeTestBatchSink(std::move(mock));
+ auto initial_spans = {message_span};
+ AddMessages(initial_spans, batch_sink);
+
+ auto response = batch_sink->AsyncPublish(MakeRequest(1)).get();
+ EXPECT_THAT(response, IsOk());
+
+ auto spans = span_catcher->GetSpans();
+ EXPECT_THAT(spans,
+ Contains(AllOf(SpanNamed("test-topic publish"), SpanIsRoot())));
+}
+#endif
+
 TEST(TracingBatchSink, AsyncPublishOnlyIncludeSampledLink) {
  namespace sc = ::opentelemetry::trace::SemanticConventions;
  // Create span before the span catcher so it is not sampled.

google/cloud/testing_util/opentelemetry_matchers.h

@@ -150,6 +150,12 @@ MATCHER_P(SpanWithParent, span,
  return actual == span->GetContext().span_id();
 }
 
+MATCHER(SpanIsRoot, "is root span") {
+ auto const actual = arg->GetParentSpanId() == opentelemetry::trace::SpanId();
+ *result_listener << "is root span: " << (actual ? "true" : "false");
+ return actual;
+}
+
 MATCHER_P(SpanNamed, name, "has name: " + std::string{name}) {
  auto const& actual = arg->GetName();
  *result_listener << "has name: " << actual;