feat(vertx): inject context to downstream

Closes #15284

Author: squakez

instrumentation/vertx/vertx-web-3.0/javaagent/build.gradle.kts

@@ -13,6 +13,8 @@ muzzle {
 
 dependencies {
   compileOnly("io.vertx:vertx-web:3.0.0")
+  compileOnly("io.vertx:vertx-codegen:3.0.0")
+  compileOnly("io.vertx:vertx-docgen:3.0.0")
 
   // We need both version as different versions of Vert.x use different versions of Netty
   testInstrumentation(project(":instrumentation:netty:netty-4.0:javaagent"))

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 +53,21 @@ 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);