docs: private Builder buildMongoClientOptions(Builder builder, String group) {
  		if (setting == null) {
  			return builder;
  		}
  
  		if (group == null) {
  			group = StrUtil.EMPTY;
  		} else {
  			group = group + StrUtil.DOT;
  		}
  
  		// 每个主机答应的连接数（每个主机的连接池大小），当连接池被用光时，会被阻塞住
  		Integer connectionsPerHost = setting.getInt(group + "connectionsPerHost");
  		if (StrUtil.isBlank(group) == false && connectionsPerHost == null) {
  			connectionsPerHost = setting.getInt("connectionsPerHost");
  		}
  		if (connectionsPerHost != null) {
  			builder.connectionsPerHost(connectionsPerHost);
  			log.debug("MongoDB connectionsPerHost: {}", connectionsPerHost);
  		}
  
  		// multiplier for connectionsPerHost for # of threads that can block if connectionsPerHost is 10, and threadsAllowedToBlockForConnectionMultiplier is 5, then 50 threads can block more than
  		// that and an exception will be throw --int
  		Integer threadsAllowedToBlockForConnectionMultiplier = setting.getInt(group + "threadsAllowedToBlockForConnectionMultiplier");
  		if (StrUtil.isBlank(group) == false && threadsAllowedToBlockForConnectionMultiplier == null) {
  			threadsAllowedToBlockForConnectionMultiplier = setting.getInt("threadsAllowedToBlockForConnectionMultiplier");
  		}
  		if (threadsAllowedToBlockForConnectionMultiplier != null) {
  			builder.threadsAllowedToBlockForConnectionMultiplier(threadsAllowedToBlockForConnectionMultiplier);
  			log.debug("MongoDB threadsAllowedToBlockForConnectionMultiplier: {}", threadsAllowedToBlockForConnectionMultiplier);
  		}
  
  		// 被阻塞线程从连接池获取连接的最长等待时间（ms） --int
  		Integer connectTimeout = setting.getInt(group + "connectTimeout");
  		if (StrUtil.isBlank(group) == false && connectTimeout == null) {
  			setting.getInt("connectTimeout");
  		}
  		if (connectTimeout != null) {
  			builder.connectTimeout(connectTimeout);
  			log.debug("MongoDB connectTimeout: {}", connectTimeout);
  		}
  
  		// 套接字超时时间;该值会被传递给Socket.setSoTimeout(int)。默以为0（无穷） --int
  		Integer socketTimeout = setting.getInt(group + "socketTimeout");
  		if (StrUtil.isBlank(group) == false && socketTimeout == null) {
  			setting.getInt("socketTimeout");
  		}
  		if (socketTimeout != null) {
  			builder.socketTimeout(socketTimeout);
  			log.debug("MongoDB socketTimeout: {}", socketTimeout);
  		}
  
  		return builder;
  	}