code: private void sendSpokeHeartbeats()
    {
      for (ServerTarget target : _targets) {
        ServerHeartbeat server = target.getServer();
        
        if (server.getRack() != _rack) {
          continue;
        }
        
        if (isHub(server)) {
          target.sendServerHeartbeat(getServerSelf().getUpdate());
        }
      }
    }
docs: Sends a server status message to the hub servers. The server message
  contains the status for the current server.