为什么在节点中连接mongodb总是得到错误＆＃34;列表中没有有效的种子服务器＆＃34;

Question

我编写了一个简单的节点应用程序，并处理一个简单的MongoDB写入和读取。

该应用程序最初运行正常，但是，一段时间后，服务器被卡住，并注销：

{ [MongoError: no valid seed servers in list] name: 'MongoError', message: 'no valid seed servers in list' }

连接代码如下：

var mongodb = require('mongodb');
var MongoClient = mongodb.MongoClient;
var url = 'mongodb://mongodb-server-2.xxx.com:27000,mongodb-server-3.xxx.com:27000,mongodb-arbiter-0.fotor.mobi:27000/mydb';
var options = {
db: {
    readPreference: mongodb.ReadPreference.PRIMARY,
    slaveOk: true
},
replSet: {
    replicaSet: 'ei-repl0'
},
server: {
    w: 1,
    autoReconnect: true
}};
MongoClient.connect(url,options, function(err, db) {
    //do some mongodb process...
})

rs.status（）就像这样：

{
"set" : "ei-repl0",
"date" : ISODate("2016-01-30T03:07:22.515Z"),
"myState" : 1,
"members" : [ 
    {
        "_id" : 0,
        "name" : "mongodb-server-2.xxx.com:27000",
        "health" : 1.0000000000000000,
        "state" : 2,
        "stateStr" : "SECONDARY",
        "uptime" : 1.89144e+006,
        "optime" : Timestamp(1454123242, 1),
        "optimeDate" : ISODate("2016-01-30T03:07:22.000Z"),
        "lastHeartbeat" : ISODate("2016-01-30T03:07:22.161Z"),
        "lastHeartbeatRecv" : ISODate("2016-01-30T03:07:22.050Z"),
        "pingMs" : 1,
        "syncingTo" : "mongodb-server-3.xxx.com:27000",
        "configVersion" : 5
    }, 
    {
        "_id" : 1,
        "name" : "mongodb-server-3.xxx.com:27000",
        "health" : 1.0000000000000000,
        "state" : 1,
        "stateStr" : "PRIMARY",
        "uptime" : 1.89333e+006,
        "optime" : Timestamp(1454123242, 2),
        "optimeDate" : ISODate("2016-01-30T03:07:22.000Z"),
        "electionTime" : Timestamp(1452231590, 1),
        "electionDate" : ISODate("2016-01-08T05:39:50.000Z"),
        "configVersion" : 5,
        "self" : true
    }, 
    {
        "_id" : 2,
        "name" : "mongodb-arbiter-0.xxx.com:27000",
        "health" : 1.0000000000000000,
        "state" : 7,
        "stateStr" : "ARBITER",
        "uptime" : 1.89176e+006,
        "lastHeartbeat" : ISODate("2016-01-30T03:07:20.974Z"),
        "lastHeartbeatRecv" : ISODate("2016-01-30T03:07:22.434Z"),
        "pingMs" : 1,
        "configVersion" : 5
    }
],
"ok" : 1.0000000000000000
}

可能是什么问题？