Fixed first span metadata processing.

Author: AlexeyKuznetsov-DD

dd-trace-core/src/main/java/datadog/trace/common/writer/ddagent/TraceMapperV1.java

@@ -83,23 +83,23 @@ public TraceMapperV1() {
   public void map(List<? extends CoreSpan<?>> trace, Writable writable) {
     CoreSpan<?> firstSpan = trace.get(0);
     firstSpan.processTagsAndBaggage(spanMetadata, false);
-    Metadata meta = spanMetadata.metadata;
+    Metadata firstSpanMeta = spanMetadata.metadata;
 
     // encoded fields: 1..7, but skipping #5, as not required by tracers and set by the agent.
     writable.startMap(6);
 
     // priority = 1, the sampling priority of the trace
-    encodeField(writable, 1, meta.samplingPriority()); // TODO double check
+    encodeField(writable, 1, firstSpanMeta.samplingPriority()); // TODO double check
     // origin = 2, the optional string origin ("lambda", "rum", etc.) of the trace chunk
     encodeField(writable, 2, firstSpan.getOrigin()); // TODO double check
     // attributes = 3, a collection of key to value pairs common in all `spans`
     encodeAttributes(writable, 3, buildChunkAttributes(trace), emptyMap());
     // spans = 4, a list of spans in this chunk
-    encodeSpans(writable, 4, trace);
+    encodeSpans(writable, 4, trace, firstSpanMeta);
     // traceID = 6, the ID of the trace to which all spans in this chunk belong
     encodeField(writable, 6, firstSpan.getTraceId().to128BitBytes());
     // samplingMechanism = 7
-    encodeField(writable, 7, parseSamplingMechanism(meta.getTags()));
+    encodeField(writable, 7, parseSamplingMechanism(firstSpanMeta.getTags()));
   }
 
   private Map<String, Object> buildChunkAttributes(List<? extends CoreSpan<?>> trace) {
@@ -114,7 +114,11 @@ private Map<String, Object> buildChunkAttributes(List<? extends CoreSpan<?>> tra
     return singletonMap("service", service);
   }
 
-  private void encodeSpans(Writable writable, int fieldId, List<? extends CoreSpan<?>> spans) {
+  private void encodeSpans(
+      Writable writable,
+      int fieldId,
+      List<? extends CoreSpan<?>> spans,
+      Metadata firstSpanMetadata) {
     int spansCount = spans.size();
 
     writable.writeInt(fieldId);
@@ -123,8 +127,13 @@ private void encodeSpans(Writable writable, int fieldId, List<? extends CoreSpan
     for (int i = 0; i < spansCount; i++) {
       final CoreSpan<?> span = spans.get(i);
 
-      span.processTagsAndBaggage(spanMetadata, false);
-      Metadata meta = spanMetadata.metadata;
+      Metadata meta;
+      if (i == 0) {
+        meta = firstSpanMetadata;
+      } else {
+        span.processTagsAndBaggage(spanMetadata, false);
+        meta = spanMetadata.metadata;
+      }
       TagMap tags = meta.getTags();
       Map<String, Object> metaStruct = span.getMetaStruct();
 

dd-trace-core/src/test/groovy/datadog/trace/common/writer/ddagent/TraceMapperV1PayloadTest.groovy

@@ -24,6 +24,7 @@ import datadog.trace.bootstrap.instrumentation.api.SpanLink
 import datadog.trace.bootstrap.instrumentation.api.Tags
 import datadog.trace.common.writer.Payload
 import datadog.trace.common.writer.TraceGenerator
+import datadog.trace.core.MetadataConsumer
 import datadog.trace.test.util.DDSpecification
 import java.nio.ByteBuffer
 import java.nio.channels.WritableByteChannel
@@ -286,6 +287,54 @@ class TraceMapperV1PayloadTest extends DDSpecification {
     assertEquals([:], links[1].attributes)
   }
 
+  def "test first span tags are processed once"() {
+    setup:
+    def firstSpan = new CountingPojoSpan(
+      "service-a",
+      "operation-a",
+      "resource-a",
+      DDTraceId.ONE,
+      123L,
+      0L,
+      1000L,
+      2000L,
+      0,
+      [:],
+      [(Tags.HTTP_URL): "http://localhost:7777/"],
+      "web",
+      false,
+      PrioritySampling.SAMPLER_KEEP,
+      200,
+      null)
+
+    def secondSpan = new CountingPojoSpan(
+      "service-a",
+      "operation-b",
+      "resource-b",
+      DDTraceId.ONE,
+      456L,
+      123L,
+      1000L,
+      2000L,
+      0,
+      [:],
+      [(Tags.HTTP_URL): "http://localhost:7777/"],
+      "web",
+      false,
+      PrioritySampling.SAMPLER_KEEP,
+      200,
+      null)
+
+    TraceMapperV1 mapper = new TraceMapperV1()
+
+    when:
+    serializeMappedPayload(mapper, [[firstSpan, secondSpan]])
+
+    then:
+    assertEquals(1, firstSpan.processTagsAndBaggageCount)
+    assertEquals(1, secondSpan.processTagsAndBaggageCount)
+  }
+
   def "test missing span links encode empty links"() {
     setup:
     def span = new TraceGenerator.PojoSpan(
@@ -1339,6 +1388,52 @@ class TraceMapperV1PayloadTest extends DDSpecification {
     }
   }
 
+  private static class CountingPojoSpan extends TraceGenerator.PojoSpan {
+    int processTagsAndBaggageCount = 0
+
+    CountingPojoSpan(
+    String serviceName,
+    String operationName,
+    CharSequence resourceName,
+    DDTraceId traceId,
+    long spanId,
+    long parentId,
+    long start,
+    long duration,
+    int error,
+    Map<String, String> baggage,
+    Map<String, Object> tags,
+    CharSequence type,
+    boolean measured,
+    int samplingPriority,
+    int statusCode,
+    CharSequence origin) {
+      super(
+      serviceName,
+      operationName,
+      resourceName,
+      traceId,
+      spanId,
+      parentId,
+      start,
+      duration,
+      error,
+      baggage,
+      tags,
+      type,
+      measured,
+      samplingPriority,
+      statusCode,
+      origin)
+    }
+
+    @Override
+    void processTagsAndBaggage(MetadataConsumer consumer) {
+      processTagsAndBaggageCount++
+      super.processTagsAndBaggage(consumer)
+    }
+  }
+
   private static class ByteArrayChannel implements WritableByteChannel {
     private byte[] data = new byte[0]