Datadog: fix names in Span::spawnChild

changelogs/current.yaml

@@ -123,6 +123,9 @@ bug_fixes:
   change: |
     Fixed a bug where a histogram bucket counts were wrong. Additionally, the number of buckets is fixed and is now
     one element larger than the explicit bounds elements, as required by the specification.
+- area: tracing
+  change: |
+    Fixed a bug where child spans produced by the Datadog tracer would have an incorrect operation name.
 - area: DNS
   change: |
     Fixed a race condition that when multiple requests with the same authority header are sent to Envoy, sometimes some requests

source/extensions/tracers/datadog/span.cc

@@ -90,8 +90,13 @@ Tracing::SpanPtr Span::spawnChild(const Tracing::Config&, const std::string& nam
 
   // The OpenTracing implementation ignored the `Tracing::Config` argument,
   // so we will as well.
+  // The `name` parameter to this function more closely matches Datadog's
+  // concept of "resource name." Datadog's "span name," or "operation name,"
+  // instead describes the category of operation being performed, which here
+  // we hard-code.
   datadog::tracing::SpanConfig config;
-  config.name = name;
+  config.name = "envoy.proxy";
+  config.resource = name;
   config.start = estimateTime(start_time);
 
   return std::make_unique<Span>(span_->create_child(config));

test/extensions/tracers/datadog/BUILD

@@ -19,6 +19,7 @@ envoy_extension_cc_test(
         "dict_util_test.cc",
         "event_scheduler_test.cc",
         "logger_test.cc",
+        "naming_test.cc",
         "span_test.cc",
         "time_util_test.cc",
         "tracer_stats_test.cc",

test/extensions/tracers/datadog/naming_test.cc

@@ -0,0 +1,223 @@
+/**
+ * The tests in this file aren't specific to a class, but instead test all
+ * behavior related to spans' "operation name" (a.k.a. "span name"),
+ * "resource name," and "service name."
+ *
+ * Datadog's model of a span is different from Envoy's. Each Datadog span,
+ * in addition to having a "service name" and an "operation name," also has a
+ * "resource name." The operation name indicates the _kind_ of operation
+ * that is being performed by the service, whereas the resource name contains
+ * more specifics about what is being operated upon, or about what is doing the
+ * operating. Envoy has no notion of "resource name," and instead uses
+ * operation name and tags for this purpose.
+ *
+ * When Envoy's tracing interface indicates an operation name, the Datadog
+ * tracer translates it into a resource name instead. The actual Datadog
+ * operation name is always hard-coded to the value "envoy.proxy".
+ *
+ * Finally, each span's "service name" is derived either from the tracer's
+ * configuration or a hard-coded default, which is "envoy".
+ *
+ * The tests in this file verify all of this behavior for a variety of
+ * scenarios where spans are created or modified.
+ */
+
+#include "source/extensions/tracers/datadog/config.h"
+#include "source/extensions/tracers/datadog/span.h"
+#include "source/extensions/tracers/datadog/tracer.h"
+
+#include "test/mocks/stream_info/mocks.h"
+#include "test/mocks/thread_local/mocks.h"
+#include "test/mocks/tracing/mocks.h"
+#include "test/mocks/upstream/cluster_manager.h"
+#include "test/test_common/simulated_time_system.h"
+#include "test/test_common/utility.h"
+
+#include "gtest/gtest.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace Tracers {
+namespace Datadog {
+namespace {
+
+template <typename Config> Config makeConfig(const std::string& yaml) {
+  Config result;
+  TestUtility::loadFromYaml(yaml, result);
+  return result;
+}
+
+class DatadogTracerNamingTest : public testing::Test {
+public:
+  DatadogTracerNamingTest();
+
+protected:
+  /**
+   * Verify that a tracer configured using the specified \p config_yaml
+   * produces spans and child spans having the specified
+   * \p expected_service_name.
+   * @param config_yaml YAML representation of a
+   *    \c type.googleapis.com/envoy.config.trace.v3.DatadogConfig
+   * @param expected_service_name service name to expect each span to have
+   */
+  void serviceNameTest(const std::string& config_yaml, const std::string& expected_service_name);
+
+  /**
+   * Assign through the specified \p result a pointer to the underlying
+   * \c datadog::tracing::Span to which the specified \p span refers.
+   * If \p span does not refer to a Datadog span, then this function triggers a
+   * fatal test assertion.
+   * An output parameter is used because the \c ASSERT_* macros require that
+   * the enclosing function have \c void return type.
+   * @param result pointer to the output value to overwrite
+   * @param span pointer to an Envoy span that refers to a Datadog span
+   */
+  static void asDatadogSpan(const datadog::tracing::Span** result, const Tracing::SpanPtr& span);
+
+  NiceMock<Upstream::MockClusterManager> cluster_manager_;
+  Stats::TestUtil::TestStore store_;
+  NiceMock<ThreadLocal::MockInstance> thread_local_slot_allocator_;
+  Event::SimulatedTimeSystem time_;
+  NiceMock<StreamInfo::MockStreamInfo> stream_info_;
+};
+
+DatadogTracerNamingTest::DatadogTracerNamingTest() {
+  cluster_manager_.initializeClusters({"fake_cluster"}, {});
+  cluster_manager_.thread_local_cluster_.cluster_.info_->name_ = "fake_cluster";
+  cluster_manager_.initializeThreadLocalClusters({"fake_cluster"});
+}
+
+void DatadogTracerNamingTest::asDatadogSpan(const datadog::tracing::Span** result,
+                                            const Tracing::SpanPtr& span) {
+  ASSERT_TRUE(span);
+  const auto as_dd_span_wrapper = dynamic_cast<Span*>(span.get());
+  ASSERT_NE(nullptr, as_dd_span_wrapper);
+
+  const datadog::tracing::Optional<datadog::tracing::Span>& maybe_dd_span =
+      as_dd_span_wrapper->impl();
+  ASSERT_TRUE(maybe_dd_span);
+  *result = &*maybe_dd_span;
+}
+
+void DatadogTracerNamingTest::serviceNameTest(const std::string& config_yaml,
+                                              const std::string& expected_service_name) {
+  auto config_proto = makeConfig<envoy::config::trace::v3::DatadogConfig>(config_yaml);
+
+  Tracer tracer{config_proto.collector_cluster(),
+                config_proto.collector_hostname(),
+                DatadogTracerFactory::makeConfig(config_proto),
+                cluster_manager_,
+                *store_.rootScope(),
+                thread_local_slot_allocator_};
+
+  // Any values will do for the sake of this test. What we care about is the
+  // `expected_service_name`.
+  Tracing::Decision decision;
+  decision.reason = Tracing::Reason::Sampling;
+  decision.traced = true;
+  const std::string operation_name = "some.operation.name";
+  Tracing::TestTraceContextImpl context{};
+
+  const Tracing::SpanPtr span =
+      tracer.startSpan(Tracing::MockConfig{}, context, stream_info_, operation_name, decision);
+  const datadog::tracing::Span* dd_span;
+  asDatadogSpan(&dd_span, span);
+
+  EXPECT_EQ(expected_service_name, dd_span->service_name());
+
+  const auto child_start = time_.timeSystem().systemTime();
+  const std::string child_operation_name = "some.other.operation.name";
+  const Tracing::SpanPtr child =
+      span->spawnChild(Tracing::MockConfig{}, child_operation_name, child_start);
+  const datadog::tracing::Span* dd_child;
+  asDatadogSpan(&dd_child, child);
+
+  EXPECT_EQ(expected_service_name, dd_child->service_name());
+}
+
+TEST_F(DatadogTracerNamingTest, ServiceNameConfigured) {
+  // If you specify a `service_name` in the tracer configuration, then spans
+  // created will have that service name.
+  serviceNameTest(R"EOF(
+    collector_cluster: fake_cluster
+    service_name: mr_bigglesworth
+   )EOF",
+                  "mr_bigglesworth");
+}
+
+TEST_F(DatadogTracerNamingTest, ServiceNameDefault) {
+  // If you don't specify a `service_name` in the tracer configuration, then
+  // spans created will have the default service name, which is "envoy".
+  serviceNameTest(R"EOF(
+    collector_cluster: fake_cluster
+   )EOF",
+                  "envoy");
+}
+
+TEST_F(DatadogTracerNamingTest, OperationNameAndResourceName) {
+  // Concerns:
+  //
+  // - The span returned by `Tracer::startSpan` has as its resource name the
+  //   operation name passed to `Tracer::startSpan`, and has as its operation
+  //   name "envoy.proxy".
+  // - The span returned by `Span::spawnChild` has as its resource name the
+  //   operation name passed to `Tracer::spawnChild`, and has as its operation
+  //   name "envoy.proxy".
+  // - `Span::setOperation` sets the resource name of the span, but does not
+  //   change the operation name.
+
+  auto config_proto = makeConfig<envoy::config::trace::v3::DatadogConfig>(R"EOF(
+    collector_cluster: fake_cluster
+   )EOF");
+
+  Tracer tracer{config_proto.collector_cluster(),
+                config_proto.collector_hostname(),
+                DatadogTracerFactory::makeConfig(config_proto),
+                cluster_manager_,
+                *store_.rootScope(),
+                thread_local_slot_allocator_};
+
+  // Any values will do for the sake of this test. What we care about are the
+  // operation names and the resource names.
+  Tracing::Decision decision;
+  decision.reason = Tracing::Reason::Sampling;
+  decision.traced = true;
+  Tracing::TestTraceContextImpl context{};
+
+  const std::string operation_name = "some.operation.name";
+  const Tracing::SpanPtr span =
+      tracer.startSpan(Tracing::MockConfig{}, context, stream_info_, operation_name, decision);
+  const datadog::tracing::Span* dd_span;
+  asDatadogSpan(&dd_span, span);
+
+  EXPECT_EQ("envoy.proxy", dd_span->name());
+  EXPECT_EQ(operation_name, dd_span->resource_name());
+
+  const std::string new_operation_name = "some.new.operation.name";
+  span->setOperation(new_operation_name);
+
+  EXPECT_EQ("envoy.proxy", dd_span->name());
+  EXPECT_EQ(new_operation_name, dd_span->resource_name());
+
+  const auto child_start = time_.timeSystem().systemTime();
+  const std::string child_operation_name = "some.child.operation.name";
+  const Tracing::SpanPtr child =
+      span->spawnChild(Tracing::MockConfig{}, child_operation_name, child_start);
+  const datadog::tracing::Span* dd_child;
+  asDatadogSpan(&dd_child, child);
+
+  EXPECT_EQ("envoy.proxy", dd_child->name());
+  EXPECT_EQ(child_operation_name, dd_child->resource_name());
+
+  const std::string child_new_operation_name = "some.child.new.operation.name";
+  child->setOperation(child_new_operation_name);
+
+  EXPECT_EQ("envoy.proxy", dd_child->name());
+  EXPECT_EQ(child_new_operation_name, dd_child->resource_name());
+}
+
+} // namespace
+} // namespace Datadog
+} // namespace Tracers
+} // namespace Extensions
+} // namespace Envoy

test/extensions/tracers/datadog/span_test.cc

@@ -206,7 +206,11 @@ TEST_F(DatadogTracerSpanTest, SpawnChild) {
   EXPECT_NE(nullptr, child_ptr);
   const datadog::tracing::SpanData& child = *child_ptr;
   EXPECT_EQ(estimateTime(child_start).wall, child.start.wall);
-  EXPECT_EQ("child", child.name);
+  // Setting the operation name actually sets the resource name, because
+  // Envoy's notion of operation name more closely matches Datadog's notion of
+  // resource name. The actual operation name is hard-coded as "envoy.proxy".
+  EXPECT_EQ("child", child.resource);
+  EXPECT_EQ("envoy.proxy", child.name);
   EXPECT_EQ(id_, child.trace_id);
   EXPECT_EQ(id_, child.span_id);
   EXPECT_EQ(id_, child.parent_id);