private static List<Client> findDepends(String indexName) {
   clientsLock.r.lock();
   try {
     ArrayList<Client> list = new ArrayList<Client>();
     for (Client client : CLIENTS.values()) {
       IndexConfig indexConfig = client.getIndex().getIndexConfig();
       if (indexConfig.isMulti())
         if (indexConfig.isIndexMulti(indexName)) {
           list.add(client);
         }
     }
     return list;
   } finally {
     clientsLock.r.unlock();
   }
 }