WIP

Author: jandro996

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java

@@ -174,6 +174,10 @@ public Context startSpan(REQUEST_CARRIER carrier, Context parentContext) {
     extracted = startInferredProxySpan(parentContext, extracted);
     AgentSpan span =
         tracer().startSpan(instrumentationName, spanName(), extracted).setMeasured(true);
+    // Register service-entry span with inferred proxy span (if present) so that premature
+    // finish calls from child spans (e.g., Spring MVC handler) are deferred until the
+    // service-entry span finishes (after the response status is known).
+    registerServiceEntrySpanInInferredProxy(parentContext, span);
     // Apply RequestBlockingAction if any
     Flow<Void> flow = callIGCallbackRequestHeaders(span, carrier);
     if (flow.getAction() instanceof RequestBlockingAction) {
@@ -193,6 +197,14 @@ protected AgentSpanContext startInferredProxySpan(Context context, AgentSpanCont
     return span.start(extracted);
   }
 
+  private void registerServiceEntrySpanInInferredProxy(
+      Context parentContext, AgentSpan serviceEntrySpan) {
+    InferredProxySpan inferredProxy = InferredProxySpan.fromContext(parentContext);
+    if (inferredProxy != null) {
+      inferredProxy.registerServiceEntrySpan(serviceEntrySpan);
+    }
+  }
+
   private final DataStreamsTransactionTracker.TransactionSourceReader
       DSM_TRANSACTION_SOURCE_READER =
           (source, headerName) -> {

dd-trace-core/src/main/java/datadog/trace/common/writer/ddagent/TraceMapperV0_4.java

@@ -71,7 +71,10 @@ public void accept(Metadata metadata) {
 
       TagMap tags = metadata.getTags();
 
-      final boolean writeSamplingPriority = firstSpanInTrace || lastSpanInTrace;
+      // Also write on top-level spans so that inferred proxy spans (which may be in the middle
+      // of the serialized list due to phased-finish ordering) always carry the sampling decision.
+      final boolean writeSamplingPriority =
+          firstSpanInTrace || lastSpanInTrace || metadata.topLevel();
       final UTF8BytesString processTags = firstSpanInPayload ? metadata.processTags() : null;
       int metaSize =
           metadata.getBaggage().size()

dd-trace-core/src/main/java/datadog/trace/common/writer/ddagent/TraceMapperV0_5.java

@@ -202,7 +202,10 @@ MetaWriter forSpan(boolean firstInTrace, boolean lastInTrace, boolean firstInPay
 
     @Override
     public void accept(Metadata metadata) {
-      final boolean writeSamplingPriority = firstSpanInTrace || lastSpanInTrace;
+      // Also write on top-level spans so that inferred proxy spans (which may be in the middle
+      // of the serialized list due to phased-finish ordering) always carry the sampling decision.
+      final boolean writeSamplingPriority =
+          firstSpanInTrace || lastSpanInTrace || metadata.topLevel();
       final UTF8BytesString processTags = firstSpanInPayload ? metadata.processTags() : null;
 
       TagMap tags = metadata.getTags();