node连接阿里云的mongodb时出现no primary found in replicaset错误

使用的是replica set url：mongodb://root:**@xxx1:3717,xxx2:3717/admin?replicaSet=mgset-xxxx

具体的代码是：

var mongodb = require('mongodb');
var MongoClient = mongodb.MongoClient;
var url = 'mongodb://root:****@xxx1:3717,xxx2:3717/admin?replicaSet=mgset-xxxx';
MongoClient.connect(url, (err, db) => {
    if (err) {
      console.log(err);
      return;
    }
    console.log('success');
  });

然后收到错误

{ [MongoError: no primary found in replicaset]
  name: 'MongoError',
  message: 'no primary found in replicaset' }

请教一下这个大概是什么问题？