Node.js can'；mongoose中不能连接多个数据库

我想使用

mongodb

中的两个数据库，使用

createConnection

覆盖

mongoose

exports.mongooseMaster = mongoose.createConnection('mongodb://192.168.2.10:27017/Master', function (err, res) {
   if (err) {
      console.log ('ERROR connecting to: remote Master ' + err);
  } else {
      console.log ('Successfully connected to: remote Master');
  }
});

// Connect to Database
exports.mongoosetime = mongoose.createConnection('mongodb://192.168.2.10:27017/Planner2', function (err, res) {
if (err) {
      console.log ('ERROR connecting to: remote Planner2 ' + err);
  } else {
      console.log ('Successfully connected to: remote Planner2');
  };
});

当我执行这段代码时，我看到只有Planner2数据库创建了主数据库，而不是主数据库。但我在控制台里得到了这些线

Successfully connected to: remote Master
Successfully connected to: remote Planner2

---

有什么问题吗？

但是为什么要两个连接？从同一个连接获取不同的DB是否足够？