don't override route with / in vertx instrumentation (#8881)

Author: vandonr

dd-java-agent/instrumentation/vertx-web-3.4/src/main/java/datadog/trace/instrumentation/vertx_3_4/server/EndHandlerWrapper.java

@@ -7,6 +7,7 @@
 import static datadog.trace.instrumentation.vertx_3_4.server.VertxDecorator.DECORATE;
 
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
+import datadog.trace.bootstrap.instrumentation.api.Tags;
 import io.vertx.core.Handler;
 import io.vertx.ext.web.RoutingContext;
 
@@ -29,7 +30,10 @@ public void handle(final Void event) {
         actual.handle(event);
       }
     } finally {
-      if (path != null && parentSpan != null) {
+      if (path != null
+          && parentSpan != null
+          // do not override route with a "/" if it's already set (it's probably more meaningful)
+          && !(path.equals("/") && parentSpan.getTag(Tags.HTTP_ROUTE) != null)) {
         HTTP_RESOURCE_DECORATOR.withRoute(
             parentSpan, routingContext.request().rawMethod(), path, true);
       }

dd-java-agent/instrumentation/vertx-web-4.0/src/main/java/datadog/trace/instrumentation/vertx_4_0/server/EndHandlerWrapper.java

@@ -7,6 +7,7 @@
 import static datadog.trace.instrumentation.vertx_4_0.server.VertxDecorator.DECORATE;
 
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
+import datadog.trace.bootstrap.instrumentation.api.Tags;
 import io.vertx.core.Handler;
 import io.vertx.ext.web.RoutingContext;
 
@@ -29,7 +30,10 @@ public void handle(final Void event) {
         actual.handle(event);
       }
     } finally {
-      if (path != null && parentSpan != null) {
+      if (path != null
+          && parentSpan != null
+          // do not override route with a "/" if it's already set (it's probably more meaningful)
+          && !(path.equals("/") && parentSpan.getTag(Tags.HTTP_ROUTE) != null)) {
         HTTP_RESOURCE_DECORATOR.withRoute(
             parentSpan, routingContext.request().method().name(), path, true);
       }