Refactor multiple implementations of W3C trace context building into a dedicated helper

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/AbstractConnectionInstrumentation.java

@@ -33,7 +33,7 @@ public Map<String, String> contextStore() {
   @Override
   public String[] helperClassNames() {
     return new String[] {
-      packageName + ".JDBCDecorator",
+      "datadog.trace.core.propagation.W3CTraceParent", packageName + ".JDBCDecorator",
     };
   }
 

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/AbstractPreparedStatementInstrumentation.java

@@ -40,7 +40,7 @@ public AbstractPreparedStatementInstrumentation(
   @Override
   public String[] helperClassNames() {
     return new String[] {
-      packageName + ".JDBCDecorator",
+      "datadog.trace.core.propagation.W3CTraceParent", packageName + ".JDBCDecorator",
     };
   }
 

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/DBMCompatibleConnectionInstrumentation.java

@@ -78,6 +78,7 @@ public DBMCompatibleConnectionInstrumentation() {
   @Override
   public String[] helperClassNames() {
     return new String[] {
+      "datadog.trace.core.propagation.W3CTraceParent",
       packageName + ".JDBCDecorator",
       packageName + ".SQLCommenter",
       "datadog.trace.bootstrap.instrumentation.dbm.SharedDBCommenter",

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/DriverInstrumentation.java

@@ -49,7 +49,7 @@ public Map<String, String> contextStore() {
   @Override
   public String[] helperClassNames() {
     return new String[] {
-      packageName + ".JDBCDecorator",
+      "datadog.trace.core.propagation.W3CTraceParent", packageName + ".JDBCDecorator",
     };
   }
 

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/JDBCDecorator.java

@@ -8,7 +8,6 @@
 import static datadog.trace.bootstrap.instrumentation.api.Tags.*;
 
 import datadog.trace.api.Config;
-import datadog.trace.api.DDSpanId;
 import datadog.trace.api.DDTraceId;
 import datadog.trace.api.naming.SpanNaming;
 import datadog.trace.api.telemetry.LogCollector;
@@ -23,6 +22,7 @@
 import datadog.trace.bootstrap.instrumentation.jdbc.DBInfo;
 import datadog.trace.bootstrap.instrumentation.jdbc.DBQueryInfo;
 import datadog.trace.bootstrap.instrumentation.jdbc.JDBCConnectionUrlParser;
+import datadog.trace.core.propagation.W3CTraceParent;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.sql.Connection;
@@ -257,16 +257,6 @@ private AgentSpan withQueryInfo(AgentSpan span, DBQueryInfo info, CharSequence c
     return span.setTag(Tags.COMPONENT, component);
   }
 
-  public String traceParent(AgentSpan span, int samplingPriority) {
-    StringBuilder sb = new StringBuilder(55);
-    sb.append("00-");
-    sb.append(span.getTraceId().toHexString());
-    sb.append('-');
-    sb.append(DDSpanId.toHexStringPadded(span.getSpanId()));
-    sb.append(samplingPriority > 0 ? "-01" : "-00");
-    return sb.toString();
-  }
-
   public boolean isOracle(final DBInfo dbInfo) {
     return "oracle".equals(dbInfo.getType());
   }
@@ -294,7 +284,7 @@ public void setAction(AgentSpan span, Connection connection) {
       if (priority == null) {
         return;
       }
-      final String traceContext = DD_INSTRUMENTATION_PREFIX + DECORATE.traceParent(span, priority);
+      final String traceContext = DD_INSTRUMENTATION_PREFIX + W3CTraceParent.from(span);
 
       connection.setClientInfo("OCSID.ACTION", traceContext);
 
@@ -380,7 +370,7 @@ public void setApplicationName(AgentSpan span, Connection connection) {
       if (priority == null) {
         return;
       }
-      final String traceParent = DECORATE.traceParent(span, priority);
+      final String traceParent = W3CTraceParent.from(span);
       final String traceContext = "_DD_" + traceParent;
 
       connection.setClientInfo("ApplicationName", traceContext);

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/StatementInstrumentation.java

@@ -23,6 +23,7 @@
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
 import datadog.trace.bootstrap.instrumentation.api.AgentTracer;
 import datadog.trace.bootstrap.instrumentation.jdbc.DBInfo;
+import datadog.trace.core.propagation.W3CTraceParent;
 import java.sql.Connection;
 import java.sql.SQLException;
 import java.sql.Statement;
@@ -59,6 +60,7 @@ public Map<String, String> contextStore() {
   @Override
   public String[] helperClassNames() {
     return new String[] {
+      "datadog.trace.core.propagation.W3CTraceParent",
       packageName + ".JDBCDecorator",
       packageName + ".SQLCommenter",
       "datadog.trace.bootstrap.instrumentation.dbm.SharedDBCommenter",
@@ -119,7 +121,7 @@ public static AgentScope onEnter(
             Integer priority = span.forceSamplingDecision();
             if (priority != null) {
               if (!isSqlServer) {
-                traceParent = DECORATE.traceParent(span, priority);
+                traceParent = W3CTraceParent.from(span);
               }
               // set the dbm trace injected tag on the span
               span.setTag(DBM_TRACE_INJECTED, true);

dd-java-agent/instrumentation/mongo/common/src/main/java/datadog/trace/instrumentation/mongo/MongoCommentInjector.java

@@ -4,9 +4,9 @@
 import static datadog.trace.bootstrap.instrumentation.api.InstrumentationTags.DBM_TRACE_INJECTED;
 
 import datadog.trace.api.Config;
-import datadog.trace.api.DDSpanId;
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
 import datadog.trace.bootstrap.instrumentation.dbm.SharedDBCommenter;
+import datadog.trace.core.propagation.W3CTraceParent;
 import org.bson.BsonArray;
 import org.bson.BsonDocument;
 import org.bson.BsonString;
@@ -75,7 +75,7 @@ public static String buildComment(AgentSpan dbSpan, String hostname, String dbNa
     String dbService = dbSpan.getServiceName();
     String traceParent =
         Config.get().getDbmPropagationMode().equals(DBM_PROPAGATION_MODE_FULL)
-            ? buildTraceParent(dbSpan)
+            ? W3CTraceParent.from(dbSpan)
             : null;
 
     // Use shared comment builder directly
@@ -112,13 +112,4 @@ private static BsonValue mergeComment(BsonValue existingComment, String dbmComme
     // Incompatible type, preserve existing comment unchanged
     return existingComment;
   }
-
-  static String buildTraceParent(AgentSpan span) {
-    // W3C traceparent format: version-traceId-spanId-flags
-    return "00-" // version
-        + span.getTraceId().toHexString() // traceId
-        + '-'
-        + DDSpanId.toHexStringPadded(span.getSpanId()) // spanId
-        + (span.context().getSamplingPriority() > 0 ? "-01" : "-00");
-  }
 }

dd-java-agent/instrumentation/mongo/common/src/test/groovy/MongoCommentInjectorTest.groovy

@@ -1,6 +1,5 @@
 import datadog.trace.agent.test.InstrumentationSpecification
 import datadog.trace.api.config.TraceInstrumentationConfig
-import datadog.trace.api.sampling.PrioritySampling
 import datadog.trace.instrumentation.mongo.MongoCommentInjector
 import org.bson.BsonDocument
 import org.bson.BsonString
@@ -18,38 +17,6 @@ abstract class BaseMongoCommentInjectorTest extends InstrumentationSpecification
 }
 
 class MongoCommentInjectorTest extends BaseMongoCommentInjectorTest {
-  def "buildTraceParent with sampled flag (SAMPLER_KEEP)"() {
-    setup:
-    def span = TEST_TRACER.buildSpan("test-op").start()
-    span.setSamplingPriority(PrioritySampling.SAMPLER_KEEP, 0)
-
-    when:
-    String traceParent = MongoCommentInjector.buildTraceParent(span)
-
-    then:
-    traceParent != null
-    traceParent ==~ /00-[0-9a-f]{32}-[0-9a-f]{16}-01/
-
-    cleanup:
-    span?.finish()
-  }
-
-  def "buildTraceParent with not sampled flag (SAMPLER_DROP)"() {
-    setup:
-    def span = TEST_TRACER.buildSpan("test-op").start()
-    span.setSamplingPriority(PrioritySampling.SAMPLER_DROP, 0)
-
-    when:
-    String traceParent = MongoCommentInjector.buildTraceParent(span)
-
-    then:
-    traceParent != null
-    traceParent ==~ /00-[0-9a-f]{32}-[0-9a-f]{16}-00/
-
-    cleanup:
-    span?.finish()
-  }
-
   def "injectComment returns null when event is null"() {
     when:
     BsonDocument result = MongoCommentInjector.injectComment("test-comment", null)

dd-java-agent/instrumentation/mongo/driver-3.6/src/main/java/datadog/trace/instrumentation/mongo/DefaultServerConnection36Instrumentation.java

@@ -32,6 +32,7 @@ public String instrumentedType() {
   @Override
   public String[] helperClassNames() {
     return new String[] {
+      "datadog.trace.core.propagation.W3CTraceParent",
       packageName + ".BsonScrubber",
       packageName + ".MongoCommentInjector",
       packageName + ".MongoDecorator",

dd-java-agent/instrumentation/mongo/driver-3.8/src/main/java/datadog/trace/instrumentation/mongo/DefaultServerConnection38Instrumentation.java

@@ -33,6 +33,7 @@ public String instrumentedType() {
   public String[] helperClassNames() {
     return new String[] {
       "datadog.trace.bootstrap.instrumentation.dbm.SharedDBCommenter",
+      "datadog.trace.core.propagation.W3CTraceParent",
       packageName + ".MongoDecorator",
       packageName + ".MongoCommentInjector",
       packageName + ".BsonScrubber",

dd-trace-core/src/main/java/datadog/trace/core/propagation/W3CHttpCodec.java

@@ -70,13 +70,8 @@ public <C> void inject(
     }
 
     private <C> void injectTraceParent(DDSpanContext context, C carrier, CarrierSetter<C> setter) {
-      StringBuilder sb = new StringBuilder(TRACE_PARENT_LENGTH);
-      sb.append("00-");
-      sb.append(context.getTraceId().toHexString());
-      sb.append('-');
-      sb.append(DDSpanId.toHexStringPadded(context.getSpanId()));
-      sb.append(context.getSamplingPriority() > 0 ? "-01" : "-00");
-      setter.set(carrier, TRACE_PARENT_KEY, sb.toString());
+      String traceparent = W3CTraceParent.from(context);
+      setter.set(carrier, TRACE_PARENT_KEY, traceparent);
     }
 
     private <C> void injectTraceState(DDSpanContext context, C carrier, CarrierSetter<C> setter) {

dd-trace-core/src/main/java/datadog/trace/core/propagation/W3CTraceParent.java

@@ -0,0 +1,48 @@
+package datadog.trace.core.propagation;
+
+import datadog.trace.api.DDSpanId;
+import datadog.trace.api.DDTraceId;
+import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
+import datadog.trace.core.DDSpanContext;
+
+/**
+ * Utility class for building W3C traceparent headers.
+ *
+ * @see <a href="https://www.w3.org/TR/trace-context/#traceparent-header">W3C Trace Context</a>
+ */
+public final class W3CTraceParent {
+
+  private static final int TRACE_PARENT_LENGTH = 55;
+
+  private W3CTraceParent() {}
+
+  /**
+   * Builds a W3C traceparent header value from the given trace context components.
+   *
+   * <p>Format: {@code <version>-<traceId>-<spanId>-<flags>}
+   *
+   * @param traceId the trace id
+   * @param spanId the span id
+   * @param isSampled whether the trace was sampled or not
+   * @return the W3C traceparent header value
+   */
+  public static String from(DDTraceId traceId, long spanId, boolean isSampled) {
+    StringBuilder sb = new StringBuilder(TRACE_PARENT_LENGTH);
+    sb.append("00-");
+    sb.append(traceId.toHexString());
+    sb.append('-');
+    sb.append(DDSpanId.toHexStringPadded(spanId));
+    sb.append(isSampled ? "-01" : "-00");
+
+    return sb.toString();
+  }
+
+  public static String from(AgentSpan span) {
+    return from(span.getTraceId(), span.getSpanId(), span.context().getSamplingPriority() > 0);
+  }
+
+  public static String from(DDSpanContext spanContext) {
+    return from(
+        spanContext.getTraceId(), spanContext.getSpanId(), spanContext.getSamplingPriority() > 0);
+  }
+}

dd-trace-core/src/test/groovy/datadog/trace/core/propagation/W3CTraceParentTest.groovy

@@ -0,0 +1,32 @@
+package datadog.trace.core.propagation
+
+import datadog.trace.api.DDTraceId
+import datadog.trace.test.util.DDSpecification
+
+class W3CTraceParentTest extends DDSpecification {
+
+  def "build produces correct format with isSampled=#isSampled"() {
+    when:
+    def result = W3CTraceParent.from(traceId, spanId, isSampled)
+
+    then:
+    result == expected
+
+    where:
+    traceId                                               | spanId              | isSampled | expected
+    DDTraceId.from(1)                                     | 2                   | true      | "00-00000000000000000000000000000001-0000000000000002-01"
+    DDTraceId.from(1)                                     | 2                   | false     | "00-00000000000000000000000000000001-0000000000000002-00"
+    DDTraceId.from(1)                                     | 2                   | true      | "00-00000000000000000000000000000001-0000000000000002-01"
+    DDTraceId.fromHex("0af7651916cd43dd8448eb211c80319c") | 0x00f067aa0ba902b7L | true      | "00-0af7651916cd43dd8448eb211c80319c-00f067aa0ba902b7-01"
+    DDTraceId.from(Long.MAX_VALUE)                        | Long.MAX_VALUE      | true      | "00-00000000000000007fffffffffffffff-7fffffffffffffff-01"
+  }
+
+  def "build matches W3C traceparent format"() {
+    when:
+    def result = W3CTraceParent.from(DDTraceId.from(123456789L), 987654321L, true)
+
+    then:
+    // W3C format: version-traceId(32 hex)-spanId(16 hex)-flags(2 hex)
+    result ==~ /00-[0-9a-f]{32}-[0-9a-f]{16}-(00|01)/
+  }
+}