private void disconnectVdc(String vdcId) throws Exception {
    URI id = new URI(vdcId);
    VirtualDataCenter vdc = dbClient.queryObject(VirtualDataCenter.class, id);
    vdc.setConnectionStatus(VirtualDataCenter.ConnectionStatus.DISCONNECTED);
    dbClient.updateAndReindexObject(vdc);

    dbClient.addVdcNodesToBlacklist(vdc);
  }
 private void updateBlackListForReconnectedVdc() {
   List<URI> vdcIds = dbClient.queryByType(VirtualDataCenter.class, true);
   dbClient.clearBlackList();
   log.info("After clear, get current black list {}", dbClient.getBlacklist());
   for (URI vdcId : vdcIds) {
     VirtualDataCenter vdc = dbClient.queryObject(VirtualDataCenter.class, vdcId);
     if (vdc.getConnectionStatus() == VirtualDataCenter.ConnectionStatus.DISCONNECTED) {
       log.info("Add vdc {} with status {} to blacklist", vdc.getId(), vdc.getConnectionStatus());
       dbClient.addVdcNodesToBlacklist(vdc);
     }
   }
 }