code: private void sendHubHeartbeats()
    {
      RackHeartbeat rack = _rack;
      
      UpdateRackHeartbeat updateRack = rack.getUpdate();
      UpdatePodSystem updatePod = getUpdatePodSystem();
      
      long now = CurrentTime.currentTime();
      
      if (! isJoinComplete()) {
        updatePod = null;
      }
  
      // send hub update to all servers in the rack
      for (ServerHeartbeat rackServer : _rack.getServers()) {
        if (rackServer == null || rackServer == _serverSelf) {
          continue;
        }
  
        ServerTarget target = createTargetServer(rackServer);
        
        target.hubHeartbeat(getServerSelf().getUpdate(),
                               updateRack,
                               updatePod,
                               now);
      }
    }
docs: Sends full heartbeat messages to all targets. Hub heartbeat messages
  contains all the servers in the hub and all the pods known to the hub
  server.
  @param type