MongoDB搭建完成replica set之后，备库读无法读

背景：

mongodb:7.0.4
架构：primary+replicat set+arbiter
问题：备库不能读

1、主库查询相关数据

wp [direct: primary] test> db.col.find({"likes":{$gt:50},$or:[{"by":"菜鸟教程"},{"title":"MongoDB"}]}).pretty()
[
  {
    _id: ObjectId('65795597419293c242906af7'),
    title: 'MongoDB',
    description: 'MongoDB 是一个nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'NoSQL' ],
    likes: 100
  },
  {
    _id: ObjectId('6579566a419293c242906af8'),
    title: 'MongoDB',
    description: 'MongoDB 是一个Nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'Nosql' ],
    likes: 100
  },
  {
    _id: ObjectId('65795819419293c24290b91c'),
    titile: 'MongoDB',
    description: 'MongoDB是一个Nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'Nosql' ],
    likes: 100
  }
]

2、replica set查看

swp [direct: secondary] test> db.col.find().pretty()
MongoServerError: not primary and secondaryOk=false - consider using db.getMongo().setReadPref() or readPreference in the connection string

更换查询方式,可以查出来

swp [direct: secondary] test> db.col.find({}).readPref("secondary")
[
  {
    _id: ObjectId('65795597419293c242906af7'),
    title: 'MongoDB',
    description: 'MongoDB 是一个nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'NoSQL' ],
    likes: 100
  },
  {
    _id: ObjectId('6579566a419293c242906af8'),
    title: 'MongoDB',
    description: 'MongoDB 是一个Nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'Nosql' ],
    likes: 100
  },
  {
    _id: ObjectId('65795819419293c24290b91c'),
    titile: 'MongoDB',
    description: 'MongoDB是一个Nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'Nosql' ],
    likes: 100
  }
]

mongodb 的primary+replica set 默认情况下是不支持从库读的

3、查看help命令

swp [direct: secondary] test> rs.help()

  Replica Set Class:

    initiate                                   Initiates the replica set.
    config                                     Returns a document that contains the current replica set configuration.
    conf                                       Calls replSetConfig
    reconfig                                   Reconfigures an existing replica set, overwriting the existing replica set configuration.
    reconfigForPSASet                          Reconfigures an existing replica set, overwriting the existing replica set configuration, if the reconfiguration is a transition from a Primary-Arbiter to a Primary-Secondary-Arbiter set.
    status                                     Calls replSetGetStatus
    isMaster                                   Calls isMaster
    hello                                      Calls hello
    printSecondaryReplicationInfo              Calls db.printSecondaryReplicationInfo
    printSlaveReplicationInfo                  DEPRECATED. Use rs.printSecondaryReplicationInfo
    printReplicationInfo                       Calls db.printReplicationInfo
    add                                        Adds replica set member to replica set.
    addArb                                     Calls rs.add with arbiterOnly=true
    remove                                     Removes a replica set member.
    freeze                                     Prevents the current member from seeking election as primary for a period of time. Uses the replSetFreeze command
    stepDown                                   Causes the current primary to become a secondary which forces an election. If no stepDownSecs is provided, uses 60 seconds. Uses the replSetStepDown command
    syncFrom                                   Sets the member that this replica set member will sync from, overriding the default sync target selection logic.
    secondaryOk                                This method is deprecated. Use db.getMongo().setReadPref() instead

4、更改配置

swp [direct: secondary] test> rs.secondaryOk()
DeprecationWarning: .setSecondaryOk() is deprecated. Use .setReadPref("primaryPreferred") instead
Setting read preference from "primary" to "primaryPreferred"

5、查看结果

可以正常查询了

swp [direct: secondary] test> db.col.find()
[
  {
    _id: ObjectId('65795597419293c242906af7'),
    title: 'MongoDB',
    description: 'MongoDB 是一个nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'NoSQL' ],
    likes: 100
  },
  {
    _id: ObjectId('6579566a419293c242906af8'),
    title: 'MongoDB',
    description: 'MongoDB 是一个Nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'Nosql' ],
    likes: 100
  },
  {
    _id: ObjectId('65795819419293c24290b91c'),
    titile: 'MongoDB',
    description: 'MongoDB是一个Nosql数据库',
    by: '菜鸟教程',
    url: 'http://www.runoob.com',
    tags: [ 'mongodb', 'database', 'Nosql' ],
    likes: 100
  }
]