title: Vertx executeBlocking resulting in many threads
body: <p>I am using vertx 3.0 to run some mysql queries. Because that code is not designed for async operation I am using executeBlocking. Even though the code runs, when I use jconsole to monitor my server I find over 100 threads most being named vert.x-worker-thread-0, vert.x-eventloop-thread-1 and vertx-blocked-thread-checker. Is this caused by anything wrong with my code?</p>
  
  <pre><code>    public Handler&lt;RoutingContext&gt; getById() {
      return (routingContext) -&gt; {
          HttpServerResponse response = routingContext.response();
          String id = routingContext.request().getParam("id");
          int idAsInt = Integer.parseInt(id);
          Vertx.vertx().executeBlocking(future -&gt; {
                  Person p = svc.getPerson(idAsInt);
                  PersonDTO dto = new PersonDTO(p.getId(), p.getFirstname(), p.getName());
                  future.complete(dto);
              }, res -&gt; {
                  if (res.succeeded()) {
                      JsonUtil.setJsonResponse(response, 200, Json.encodePrettily(res.result()));
                  }
                  else {
                      JsonUtil.setJsonResponse(response, 404, new JsonObject().put("failure", res.cause().getMessage()).toString());
                  }
                  response.end();
              }
          );
      };
  }
  </code></pre>