feat(vertx): inject context to downstream

Closes #15284

Author: squakez

instrumentation/vertx/vertx-web-3.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/vertx/RoutingContextHandlerWrapper.java

@@ -5,13 +5,16 @@
 
 package io.opentelemetry.javaagent.instrumentation.vertx;
 
+import io.opentelemetry.api.GlobalOpenTelemetry;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.context.Context;
 import io.opentelemetry.context.Scope;
+import io.opentelemetry.context.propagation.TextMapSetter;
 import io.opentelemetry.instrumentation.api.instrumenter.LocalRootSpan;
 import io.opentelemetry.instrumentation.api.semconv.http.HttpServerRoute;
 import io.opentelemetry.instrumentation.api.semconv.http.HttpServerRouteSource;
 import io.vertx.core.Handler;
+import io.vertx.core.http.HttpServerRequest;
 import io.vertx.ext.web.RoutingContext;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.UndeclaredThrowableException;
@@ -37,6 +40,7 @@ public void handle(RoutingContext context) {
       route = route.substring(0, route.length() - 1);
     }
     HttpServerRoute.update(otelContext, HttpServerRouteSource.NESTED_CONTROLLER, route);
+    injectContextToDownstream(otelContext,context.request());
 
     try (Scope ignore = RouteHolder.init(otelContext, route).makeCurrent()) {
       handler.handle(context);
@@ -49,6 +53,18 @@ public void handle(RoutingContext context) {
     }
   }
 
+  private static void injectContextToDownstream(Context otelContext, HttpServerRequest serverRequest){
+    TextMapSetter<HttpServerRequest> setter = (carrier, key, value) -> {
+      if (carrier != null) {
+        carrier.headers().set(key, value);
+      }
+    };
+
+    GlobalOpenTelemetry.get().getPropagators()
+            .getTextMapPropagator()
+            .inject(otelContext, serverRequest, setter);
+  }
+
   private static String getRoute(Context otelContext, RoutingContext routingContext) {
     String route = routingContext.currentRoute().getPath();
     String existingRoute = RouteHolder.get(otelContext);