Vertx - stop method in verticle is not guaranteed - vert.x

Question

If you run the following code multiple times you will see the inconsistency: some times there are 3 lines displayed, some times there are only 2 lines displayed (the one missing is "Successfully stopped MyVerticle"). Why the .stop method is not called?
public class Main {
public static void main(String[] args) {
Vertx vertx = Vertx.vertx();
vertx.rxDeployVerticle(new MyVerticle()).subscribe();
Runtime.getRuntime().addShutdownHook(
new Thread(() -> {
//vertx.deploymentIDs().forEach( deploymentId -> vertx.undeploy(deploymentId));
vertx.close(result -> System.out.println("Result" + result));
System.out.println("Successfully stopped Vertx");
})
);
}
}
class MyVerticle extends AbstractVerticle {
#Override
public void start(Future<Void> startFuture) {
System.out.println("Successfully started MyVerticle");
startFuture.complete();
}
#Override
public void stop(Future<Void> stopFuture) {
System.out.println("Successfully stopped MyVerticle");
stopFuture.complete();
}
}

Answer 1

The method stop() is invoked when Vert.x undeploys a verticle.
When terminating your application, Vert.x will attempt to undeploy the verticles as well, but it's a race between event loop still running and your application shutting down.