code: private void doFindGroup(final Message<JsonObject> message) {
      String group = message.body().getString("group");
      if (group == null) {
        message.reply(new JsonObject().putString("status", "error").putString("message", "Invalid group name."));
        return;
      }
  
      final String address = String.format("%s.%s", cluster, group);
      context.execute(new Action<Boolean>() {
        @Override
        public Boolean perform() {
          return groups.containsKey(address);
        }
      }, new Handler<AsyncResult<Boolean>>() {
        @Override
        public void handle(AsyncResult<Boolean> result) {
          if (result.failed()) {
            message.reply(new JsonObject().putString("status", "error").putString("message", result.cause().getMessage()));
          } else if (!result.result()) {
            message.reply(new JsonObject().putString("status", "error").putString("message", "Invalid group."));
          } else {
            message.reply(new JsonObject().putString("status", "ok").putString("result", address));
          }
        }
      });
    }
docs: Finds a group in the cluster.