MongoDB集群添加、删除节点

前置

搭建集群可参考用Docker搭建MongoDB集群(副本集)并启用认证用户名密码登录

管理员用户连接MongoDB

mongosh -u admin1 -p 1234567

添加节点

1. 查看当前集群配置

rs.config()

返回结果:

{
  _id: 'rs0',
  version: 5,
  term: 5,
  members: [
    {
      _id: 0,
      host: '192.168.10.2:30001',
      arbiterOnly: false,
      buildIndexes: true,
      hidden: false,
      priority: 1,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    },
    {
      _id: 1,
      host: '192.168.10.2:30002',
      arbiterOnly: false,
      buildIndexes: true,
      hidden: false,
      priority: 1,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    },
    {
      _id: 2,
      host: '192.168.10.2:30003',
      arbiterOnly: true,
      buildIndexes: true,
      hidden: false,
      priority: 0,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    },
    {
      _id: 3,
      host: '192.168.10.2:30004',
      arbiterOnly: false,
      buildIndexes: true,
      hidden: false,
      priority: 1,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    }
  ],
  protocolVersion: Long("1"),
  writeConcernMajorityJournalDefault: true,
  settings: {
    chainingAllowed: true,
    heartbeatIntervalMillis: 2000,
    heartbeatTimeoutSecs: 10,
    electionTimeoutMillis: 10000,
    catchUpTimeoutMillis: -1,
    catchUpTakeoverDelayMillis: 30000,
    getLastErrorModes: {},
    getLastErrorDefaults: { w: 1, wtimeout: 0 },
    replicaSetId: ObjectId("63ad544635d3487bbd1a2215")
  }
}

可以看到,members数组中是节点配置,增加节点删除节点,其实就是增删操作members数组。

2.添加新节点

新节点的配置文件要与集群中的节点配置文件一致。

建议先将priority及votes设为0,即不会选为主(priority默认1),也没有投票特性(votes默认1,有投票权)。

等该节点同步完,再将priority、votes设为1。

rs.add( { host: "192.168.10.2:30005", priority: 0, votes: 0 } )

返回ok即添加完成,等待他同步完。

3. 修改新节点的priority、votes属性

新节点同步完后,状态会变为SECONDARY,然后修改priority、votes属性。

rs.config()查看一下当前配置,这里只截取了新节点的。

    {
      _id: 4,
      host: '192.168.10.2:30005',
      arbiterOnly: false,
      buildIndexes: true,
      hidden: false,
      priority: 0,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 0
    }

如果没有删除过节点,_id的值和members数组下标一致。不确定就数一下,或者输出看一下。

修改priority、votes属性

var cfg = rs.conf()
cfg.members[4].priority = 1
cfg.members[4].votes = 1
rs.reconfig(cfg)

如果修改属性遇到报错MongoServerError: Reconfig attempted to install a config that would change the implicit default write concern. Use the setDefaultRWConcern command to set a cluster-wide write concern and try the reconfig again.

可先执行这条命令,然后再修改priority、votes属性

db.adminCommand( {"setDefaultRWConcern" : 1, "defaultWriteConcern" : { "w" : 2 } } )

修改成功后再rs.config()查看配置,可以发现节点4的配置已经和其他节点一致了,至此添加节点完成

    {
      _id: 3,
      host: '192.168.10.2:30004',
      arbiterOnly: false,
      buildIndexes: true,
      hidden: false,
      priority: 1,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    },
    {
      _id: 4,
      host: '192.168.10.2:30005',
      arbiterOnly: false,
      buildIndexes: true,
      hidden: false,
      priority: 1,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    }

另外,db.printSecondaryReplicationInfo()可以查看副本节点的同步状态

source: 192.168.10.2:30002
{
  syncedTo: 'Thu Jan 05 2023 02:40:51 GMT+0000 (Coordinated Universal Time)',
  replLag: '0 secs (0 hrs) behind the primary '
}
---
source: 192.168.10.2:30004
{
  syncedTo: 'Thu Jan 05 2023 02:40:51 GMT+0000 (Coordinated Universal Time)',
  replLag: '0 secs (0 hrs) behind the primary '
}
---
source: 192.168.10.2:30005
{
  syncedTo: 'Thu Jan 05 2023 02:40:51 GMT+0000 (Coordinated Universal Time)',
  replLag: '0 secs (0 hrs) behind the primary '
}

如果用Studio 3T连接集群,刷新后可以看到当前的集群成员

image.png

删除节点

rs.remove("192.168.10.2:30004");

返回ok就是删除成功了,然后rs.config()查看一下配置,发现端口为30004的节点3已经没了

    {
      _id: 2,
      host: '192.168.10.2:30003',
      arbiterOnly: true,
      buildIndexes: true,
      hidden: false,
      priority: 0,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    },
    {
      _id: 4,
      host: '192.168.10.2:30005',
      arbiterOnly: false,
      buildIndexes: true,
      hidden: false,
      priority: 1,
      tags: {},
      secondaryDelaySecs: Long("0"),
      votes: 1
    }

Studio 3T刷新后也能看到端口为30004的节点3已经没了

image.png

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