connect-mongo无法连接到mongodb报错Error: failed to connect to [undefined:27017]

Error: failed to connect to [undefined:27017]
    at exports.ConnectionPool.<anonymous> (D:\project\nodelog\node_modules\_mongodb@1.4.38@mongodb\lib\mongodb\connection\server.js:556:25)
    at exports.ConnectionPool.emit (node:events:527:28)
    at exports.Connection.<anonymous> (D:\project\nodelog\node_modules\_mongodb@1.4.38@mongodb\lib\mongodb\connection\connection_pool.js:156:15)
    at exports.Connection.emit (node:events:527:28)
    at Socket.<anonymous> (D:\project\nodelog\node_modules\_mongodb@1.4.38@mongodb\lib\mongodb\connection\connection.js:534:10)

module.exports = {
    port: 3000, //web端口
    cookieSecret: 'cookieSecret', //cookie名称
    // 把dbUrl改为url问题解决
      url: 'mongodb://root:root@127.0.0.1:27017/nodelog', 
   // dbUrl: 'mongodb://root:root@127.0.0.1:27017/nodelog',
    //mongodb://用户名:密码@数据库ip:端口号/数据库名
};