How to notify other cluster nodes in es plugin

When I visit one node's hello plug by host:9200/_hello?name=kf, all the nodes are printed hello,kf
How can i do??

public class RestTestAction extends BaseRestHandler {

public RestTestAction(Settings settings, RestController controller, Client client) {
    super(settings, controller, client);
    controller.registerHandler(GET, "/_hello", this);
public void handleRequest(final RestRequest request, final RestChannel channel, final Client client) {
    System.out.println("hello, " + request.param("name"));
    **//TODO How to notify other cluster nodes to say hello**