Fix Synapse 3.0 instrumentation bugs and harden span propagation (#10892)

fix: fix Synapse 3.0 instrumentation bugs and harden span propagation

Three deterministic bugs fixed:

1. Key mismatch in PassthruInstrumentation: PR #9422 renamed the context
   key constant but forgot to update the hardcoded string literal in
   SynapsePassthruInstrumentation, breaking parent span propagation
   across the passthru mechanism.

2. http.url test assertion: QueryObfuscator recombines http.url with the
   query string after obfuscation. The test expected path-only but the
   actual value correctly includes the query string.

3. Missing peer.service in V1 client spans: SynapseClientDecorator
   returns relative URIs (no host), so peer.hostname was never set.
   Added peer hostname/IP/port extraction from NHttpClientConnection.

Additionally, hardened the passthru span propagation to read the server
span directly from the source connection context rather than relying
solely on activeSpan(). SourceHandler.requestReceived() dispatches to a
worker thread pool, and while java-concurrent instrumentation normally
handles context propagation across ThreadPoolExecutor, the connection-
based lookup is more robust.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fix: delegate peer tagging to BaseDecorator for IPv6 and config support

Use DECORATE.onPeerConnection() and setPeerPort() instead of manually
setting peer tags. This correctly classifies IPv6 addresses as peer.ipv6
(instead of forcing peer.ipv4) and honors the trace.peer.hostname.enabled
config toggle for peer.hostname.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Merge branch 'master' into brian.marks/fix-synapse-instrumentation-bugs

Co-authored-by: jordan-wong <61242306+jordan-wong@users.noreply.github.com>
Co-authored-by: devflow.devflow-routing-intake <devflow.devflow-routing-intake@kubernetes.us1.ddbuild.io>

Author: 3 people

dd-java-agent/instrumentation/synapse-3.0/src/main/java/datadog/trace/instrumentation/synapse3/SynapseClientInstrumentation.java

@@ -24,6 +24,7 @@
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
 import net.bytebuddy.asm.Advice;
 import org.apache.axis2.context.MessageContext;
+import org.apache.http.HttpInetConnection;
 import org.apache.http.HttpResponse;
 import org.apache.http.nio.NHttpClientConnection;
 import org.apache.synapse.transport.passthru.TargetContext;
@@ -107,6 +108,13 @@ public static void requestSubmitted(
       // populate span using details from the submitted HttpRequest (resolved URI, etc.)
       AgentSpan span = spanFromContext(scope.context());
       DECORATE.onRequest(span, TargetContext.getRequest(connection).getRequest());
+
+      // set peer info from the connection since request URIs are relative paths
+      if (connection instanceof HttpInetConnection) {
+        HttpInetConnection inetConn = (HttpInetConnection) connection;
+        DECORATE.onPeerConnection(span, inetConn.getRemoteAddress());
+        DECORATE.setPeerPort(span, inetConn.getRemotePort());
+      }
       scope.close();
     }
   }

dd-java-agent/instrumentation/synapse-3.0/src/main/java/datadog/trace/instrumentation/synapse3/SynapsePassthruInstrumentation.java

@@ -2,10 +2,13 @@
 
 import static datadog.trace.agent.tooling.bytebuddy.matcher.NameMatchers.named;
 import static datadog.trace.bootstrap.instrumentation.api.AgentTracer.activeSpan;
+import static datadog.trace.bootstrap.instrumentation.api.Java8BytecodeBridge.spanFromContext;
+import static datadog.trace.instrumentation.synapse3.SynapseClientDecorator.SYNAPSE_CONTEXT_KEY;
 import static net.bytebuddy.matcher.ElementMatchers.isMethod;
 import static net.bytebuddy.matcher.ElementMatchers.takesArgument;
 
 import com.google.auto.service.AutoService;
+import datadog.context.Context;
 import datadog.trace.agent.tooling.Instrumenter;
 import datadog.trace.agent.tooling.InstrumenterModule;
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
@@ -14,6 +17,7 @@
 import java.util.Map;
 import net.bytebuddy.asm.Advice;
 import org.apache.axis2.context.MessageContext;
+import org.apache.http.nio.NHttpServerConnection;
 
 /** Helps propagate parent spans over 'passthru' mechanism to synapse-client instrumentation. */
 @AutoService(InstrumenterModule.class)
@@ -53,10 +57,26 @@ public static void submit(@Advice.Argument(0) final MessageContext message) {
         }
       }
 
-      // use message context to propagate active spans across Synapse's 'passthru' mechanism
-      AgentSpan span = activeSpan();
+      // Propagate the server span to the client via the message context.
+      // Prefer reading the span directly from the source connection's context (where
+      // SynapseServerInstrumentation stored it) over activeSpan(). SourceHandler dispatches
+      // request processing to a worker thread pool, and while java-concurrent instrumentation
+      // normally propagates context across ThreadPoolExecutor, the connection-based lookup is
+      // more robust as it doesn't depend on automatic context propagation.
+      AgentSpan span = null;
+      Object sourceConn = message.getProperty("pass-through.Source-Connection");
+      if (sourceConn instanceof NHttpServerConnection) {
+        Object ctx =
+            ((NHttpServerConnection) sourceConn).getContext().getAttribute(SYNAPSE_CONTEXT_KEY);
+        if (ctx instanceof Context) {
+          span = spanFromContext((Context) ctx);
+        }
+      }
+      if (null == span) {
+        span = activeSpan();
+      }
       if (null != span) {
-        message.setNonReplicableProperty("dd.trace.synapse.span", span);
+        message.setNonReplicableProperty(SYNAPSE_CONTEXT_KEY, span);
       }
     }
   }

dd-java-agent/instrumentation/synapse-3.0/src/test/groovy/datadog/trace/instrumentation/synapse3/SynapseTest.groovy

@@ -247,7 +247,7 @@ abstract class SynapseTest extends VersionedNamingTestBase {
         "$Tags.SPAN_KIND" Tags.SPAN_KIND_SERVER
         "$Tags.PEER_HOST_IPV4" "127.0.0.1"
         "$Tags.PEER_PORT" Integer
-        "$Tags.HTTP_URL" "/services/SimpleStockQuoteService"
+        "$Tags.HTTP_URL" query ? "/services/SimpleStockQuoteService?${query}" : "/services/SimpleStockQuoteService"
         "$DDTags.HTTP_QUERY" query
         "$Tags.HTTP_METHOD" method
         "$Tags.HTTP_STATUS" statusCode
@@ -302,6 +302,9 @@ abstract class SynapseTest extends VersionedNamingTestBase {
       tags {
         "$Tags.COMPONENT" "synapse-client"
         "$Tags.SPAN_KIND" Tags.SPAN_KIND_CLIENT
+        "$Tags.PEER_HOSTNAME" String
+        "$Tags.PEER_HOST_IPV4" "127.0.0.1"
+        "$Tags.PEER_PORT" Integer
         "$Tags.HTTP_URL" "/services/SimpleStockQuoteService"
         "$Tags.HTTP_METHOD" method
         "$Tags.HTTP_STATUS" statusCode
@@ -311,7 +314,6 @@ abstract class SynapseTest extends VersionedNamingTestBase {
   }
 }
 
-@Flaky("Occasionally times out when receiving traces")
 class SynapseV0ForkedTest extends SynapseTest implements TestingGenericHttpNamingConventions.ClientV0 {
 
 
@@ -321,7 +323,6 @@ class SynapseV0ForkedTest extends SynapseTest implements TestingGenericHttpNamin
   }
 }
 
-@Flaky("Occasionally times out when receiving traces")
 class SynapseV1ForkedTest extends SynapseTest implements TestingGenericHttpNamingConventions.ClientV1 {
 
   @Override