docs: synchronized public void initCloud() {
  		if (groups == null || groups.length == 0) {
  			throw new DbRuntimeException("Please give replication set groups!");
  		}
  
  		if (setting == null) {
  			// 若未指定配置文件，则使用默认配置文件
  			setting = new Setting(MONGO_CONFIG_PATH, true);
  		}
  
  		final List<ServerAddress> addrList = new ArrayList<ServerAddress>();
  		for (String group : groups) {
  			addrList.add(createServerAddress(group));
  		}
  
  		final MongoCredential credentail = createCredentail(StrUtil.EMPTY);
  		try {
  			if (null == credentail) {
  				mongo = new MongoClient(addrList, buildMongoClientOptions(StrUtil.EMPTY));
  			} else {
  				mongo = new MongoClient(addrList, credentail, buildMongoClientOptions(StrUtil.EMPTY));
  			}
  		} catch (Exception e) {
  			log.error(e, "Init MongoDB connection error!");
  			return;
  		}
  
  		log.info("Init MongoDB cloud Set pool with connection to {}", addrList);
  	}