pymongo无法连接到初级

Question

我试图通过连接到复制集的主节点来实现find_one。

MongoClient(hostname, replicaSet="rs0", read_preference=ReadPreference.PRIMARY)

但它会导致一个错误：

ServerSelectionTimeoutError:没有副本集成员匹配选择器“主()”

我能够成功地使用SECONDARY_PREFERRED阅读。我也尝试过使用MongoReplicaSetClient连接，但没有成功。我猜这是因为配置不好，但我应该找什么呢？

rs.status：

rs0:PRIMARY> rs.conf()
{
       "_id" : "rs0",
       "version" : 111313,
       "protocolVersion" : NumberLong(1),
       "members" : [
               {
                       "_id" : 1,
                       "host" : "ANDROMEDA:27017",
                       "arbiterOnly" : false,
                       "buildIndexes" : true,
                       "hidden" : false,
                       "priority" : 1,
                       "tags" : {

                       },
                       "slaveDelay" : NumberLong(0),
                       "votes" : 1
               },
               {
                       "_id" : 2,
                       "host" : "mongo02.db.com:27017",
                       "arbiterOnly" : false,
                       "buildIndexes" : true,
                       "hidden" : false,
                       "priority" : 0.5,
                       "tags" : {

                       },
                       "slaveDelay" : NumberLong(0),
                       "votes" : 1
               },
               {
                       "_id" : 3,
                       "host" : "mongo03.db.com:27017",
                       "arbiterOnly" : false,
                       "buildIndexes" : true,
                       "hidden" : false,
                       "priority" : 0.5,
                       "tags" : {

                       },
                       "slaveDelay" : NumberLong(0),
                       "votes" : 1
               }
       ],
       "settings" : {
               "chainingAllowed" : true,
               "heartbeatIntervalMillis" : 2000,
               "heartbeatTimeoutSecs" : 10,
               "electionTimeoutMillis" : 10000,
               "getLastErrorModes" : {

               },
               "getLastErrorDefaults" : {
                       "w" : 1,
                       "wtimeout" : 0
               }
       }
}
rs0:SECONDARY> rs.status()
{
       "set" : "rs0",
       "date" : ISODate("2016-08-04T08:58:02.293Z"),
       "myState" : 2,
       "term" : NumberLong(90),
       "syncingTo" : "mongo03.db.com:27017",
       "heartbeatIntervalMillis" : NumberLong(2000),
       "members" : [
               {
                       "_id" : 1,
                       "name" : "ANDROMEDA:27017",
                       "health" : 1,
                       "state" : 1,
                       "stateStr" : "PRIMARY",
                       "uptime" : 2503,
                       "optime" : {
                               "ts" : Timestamp(1470299746, 1),
                               "t" : NumberLong(90)
                       },
                       "optimeDate" : ISODate("2016-08-04T08:35:46Z"),
                       "lastHeartbeat" : ISODate("2016-08-04T08:58:01.109Z"),
                       "lastHeartbeatRecv" : ISODate("2016-08-04T08:58:01.803Z"),
                       "pingMs" : NumberLong(28),
                       "electionTime" : Timestamp(1469600522, 1),
                       "electionDate" : ISODate("2016-07-27T06:22:02Z"),
                       "configVersion" : 111313
               },
               {
                       "_id" : 2,
                       "name" : "mongo02.db.com:27017",
                       "health" : 1,
                       "state" : 2,
                       "stateStr" : "SECONDARY",
                       "uptime" : 7604104,
                       "optime" : {
                               "ts" : Timestamp(1470299746, 1),
                               "t" : NumberLong(90)
                       },
                       "optimeDate" : ISODate("2016-08-04T08:35:46Z"),
                       "syncingTo" : "mongo03.db.com:27017",
                       "configVersion" : 111313,
                       "self" : true
               },
               {
                       "_id" : 3,
                       "name" : "mongo03.db.com:27017",
                       "health" : 1,
                       "state" : 2,
                       "stateStr" : "SECONDARY",
                       "uptime" : 2503,
                       "optime" : {
                               "ts" : Timestamp(1470299746, 1),
                               "t" : NumberLong(90)
                       },
                       "optimeDate" : ISODate("2016-08-04T08:35:46Z"),
                       "lastHeartbeat" : ISODate("2016-08-04T08:58:01.948Z"),
                       "lastHeartbeatRecv" : ISODate("2016-08-04T08:58:01.802Z"),
                       "pingMs" : NumberLong(28),
                       "syncingTo" : "ANDROMEDA:27017",
                       "configVersion" : 111313
               }
       ],
       "ok" : 1
}

Answer 1

在具有类似于ServerSelectionTimeoutError: No replica set members match selector "Primary()"的错误消息和复制集状态函数输出的情况下，rs.status()使用非FQDN(仙女座:27017)显示主成员，那么应用程序很可能无法解析网络上的主主机。

您可以使用运行应用程序的主机的命令行中的以下命令轻松地检查这一点：

$ dig ANDROMEDA
$ ping ANDROMEDA
$ mongo --host ANDROMEDA:27017

如果没有在运行应用程序的主机上安装Mongo Shell，则可以使用Telnet。

$ telnet ANDROMEDA 27017

这些输出将允许您检查您的应用程序主机和单核主机之间的连接性，以确定这是否导致了问题。

Answer 2

我使用这个连接字符串：

 MongoClient('mongodb://mongo01.db.com:27017,mongo02.db.com:27017,mongo03.db.com:27017/mydb',replicaSet="rs0", read_preference=ReadPreference.PRIMARY)