Align gRPC status code extraction with CSS v1.3.0 spec

dd-trace-core/src/main/java/datadog/trace/common/metrics/ConflatingMetricsAggregator.java

@@ -82,6 +82,17 @@ public final class ConflatingMetricsAggregator implements MetricsAggregator, Eve
                   value -> UTF8BytesString.create(key + ":" + value));
   private static final CharSequence SYNTHETICS_ORIGIN = "synthetics";
 
+  /**
+   * gRPC status code tag keys in priority order, matching the Go reference implementation. The
+   * first non-empty value wins.
+   */
+  private static final String[] GRPC_STATUS_CODE_KEYS = {
+    InstrumentationTags.GRPC_STATUS_CODE, // rpc.grpc.status_code
+    InstrumentationTags.GRPC_CODE, // grpc.code
+    InstrumentationTags.RPC_GRPC_STATUS_CODE, // rpc.grpc.status.code
+    InstrumentationTags.GRPC_STATUS_CODE_LEGACY // grpc.status.code
+  };
+
   private static final Set<String> ELIGIBLE_SPAN_KINDS_FOR_METRICS =
       unmodifiableSet(
           new HashSet<>(
@@ -331,8 +342,7 @@ private boolean publish(CoreSpan<?> span, boolean isTopLevel, CharSequence spanK
     CharSequence spanType = span.getType();
     String grpcStatusCode = null;
     if (spanType != null && RPC.contentEquals(spanType)) {
-      Object grpcStatusObj = span.unsafeGetTag(InstrumentationTags.GRPC_STATUS_CODE);
-      grpcStatusCode = grpcStatusObj != null ? grpcStatusObj.toString() : null;
+      grpcStatusCode = extractGrpcStatusCode(span);
     }
     MetricKey newKey =
         new MetricKey(
@@ -381,6 +391,26 @@ private boolean publish(CoreSpan<?> span, boolean isTopLevel, CharSequence spanK
     return span.getError() > 0;
   }
 
+  /**
+   * Extracts gRPC status code from a span by checking tag keys in priority order: 1.
+   * rpc.grpc.status_code 2. grpc.code 3. rpc.grpc.status.code 4. grpc.status.code
+   *
+   * <p>Returns the string value of the first non-empty tag found, or null if none are present. This
+   * matches the Go reference implementation's extraction order.
+   */
+  private static String extractGrpcStatusCode(CoreSpan<?> span) {
+    for (String key : GRPC_STATUS_CODE_KEYS) {
+      Object value = span.unsafeGetTag(key);
+      if (value != null) {
+        String strValue = value.toString();
+        if (!strValue.isEmpty()) {
+          return strValue;
+        }
+      }
+    }
+    return null;
+  }
+
   private List<UTF8BytesString> getPeerTags(CoreSpan<?> span, String spanKind) {
     if (ELIGIBLE_SPAN_KINDS_FOR_PEER_AGGREGATION.contains(spanKind)) {
       final Set<String> eligiblePeerTags = features.peerTags();

dd-trace-core/src/test/groovy/datadog/trace/common/metrics/ConflatingMetricAggregatorTest.groovy

@@ -1549,6 +1549,58 @@ class ConflatingMetricAggregatorTest extends DDSpecification {
     aggregator.close()
   }
 
+  def "should extract grpc status code using priority order: #description"() {
+    setup:
+    MetricWriter writer = Mock(MetricWriter)
+    Sink sink = Stub(Sink)
+    DDAgentFeaturesDiscovery features = Mock(DDAgentFeaturesDiscovery)
+    features.supportsMetrics() >> true
+    features.peerTags() >> []
+    ConflatingMetricsAggregator aggregator = new ConflatingMetricsAggregator(empty,
+      features, HealthMetrics.NO_OP, sink, writer, 10, queueSize, reportingInterval, SECONDS, false)
+    aggregator.start()
+
+    when:
+    CountDownLatch latch = new CountDownLatch(1)
+    def span = new SimpleSpan("service", "grpc.server", "grpc.service/Method", "rpc", true, false, false, 0, 100, 0)
+      .setTag(SPAN_KIND, "server")
+    tags.each { k, v -> span.setTag(k, v) }
+    aggregator.publish([span])
+    aggregator.report()
+    def latchTriggered = latch.await(2, SECONDS)
+
+    then:
+    latchTriggered
+    1 * writer.startBucket(1, _, _)
+    1 * writer.add(new MetricKey(
+      "grpc.service/Method",
+      "service",
+      "grpc.server",
+      null,
+      "rpc",
+      0,
+      false,
+      false,
+      "server",
+      [],
+      null,
+      null,
+      expectedGrpcStatus
+      ), _)
+    1 * writer.finishBucket() >> { latch.countDown() }
+
+    cleanup:
+    aggregator.close()
+
+    where:
+    description                                                | tags                                                                                                                                                              | expectedGrpcStatus
+    "rpc.grpc.status_code is highest priority"                 | [(InstrumentationTags.GRPC_STATUS_CODE): 0, (InstrumentationTags.GRPC_CODE): "OK", (InstrumentationTags.RPC_GRPC_STATUS_CODE): "0", (InstrumentationTags.GRPC_STATUS_CODE_LEGACY): "OK"] | "0"
+    "grpc.code used when rpc.grpc.status_code absent"          | [(InstrumentationTags.GRPC_CODE): "NOT_FOUND", (InstrumentationTags.RPC_GRPC_STATUS_CODE): "5", (InstrumentationTags.GRPC_STATUS_CODE_LEGACY): "NOT_FOUND"]        | "NOT_FOUND"
+    "rpc.grpc.status.code used when higher priority absent"    | [(InstrumentationTags.RPC_GRPC_STATUS_CODE): "14", (InstrumentationTags.GRPC_STATUS_CODE_LEGACY): "UNAVAILABLE"]                                                   | "14"
+    "grpc.status.code used as last fallback"                   | [(InstrumentationTags.GRPC_STATUS_CODE_LEGACY): "CANCELLED"]                                                                                                       | "CANCELLED"
+    "no grpc status when no tags present"                      | [:]                                                                                                                                                                | null
+  }
+
   def reportAndWaitUntilEmpty(ConflatingMetricsAggregator aggregator) {
     waitUntilEmpty(aggregator)
     aggregator.report()

internal-api/src/main/java/datadog/trace/bootstrap/instrumentation/api/InstrumentationTags.java

@@ -77,6 +77,9 @@ public class InstrumentationTags {
   public static final String STATUS_CODE = "status.code";
   public static final String STATUS_DESCRIPTION = "status.description";
   public static final String GRPC_STATUS_CODE = "rpc.grpc.status_code";
+  public static final String GRPC_CODE = "grpc.code";
+  public static final String RPC_GRPC_STATUS_CODE = "rpc.grpc.status.code";
+  public static final String GRPC_STATUS_CODE_LEGACY = "grpc.status.code";
   public static final String MESSAGE_TYPE = "message.type";
   public static final String MESSAGE_SIZE = "message.size";
   public static final String HYSTRIX_COMMAND = "hystrix.command";