Mongodb副本集添加節點，你學會了嗎？

作者：數據庫干貨鋪 2023-03-14 23:24:27

Mongodb副本集架構運行一段時間后如果業務發展需要新增新的成員，或者遷移集群，則可以參考本文處理。

1、準備工作

有一套mongodb 副本集的集群，部署方式參考 mongodb 4.0副本集搭建。

準備一個新節點，使用和原副本集版本一致的mongodb。

拷貝原副本集中的配置文件、keyfile文件，并注意修改keyfile文件的權限（600）。

節點	角色
192.168.56.199:27017	PRIMARY
192.168.56.198:27018	SECONDARY
192.168.56.199:27018	ARBITER

準備加入的新節點： 192.168.56.197:27017。

2、添加節點

（1）啟動新節點

例如，原節點的版本是4.2.8，新節點版本一致，路徑一致，然后啟動新節點。

/usr/local/mongodb/bin/mongod -f /data/mongodb/27017/etc/mongodb.conf

（2）主庫上查看當前節點及配置信息

使用rs.config()查看配置信息。

test12:PRIMARY> rs.config()
{
  "_id" : "test12",
  "version" : 1,
  "protocolVersion" : NumberLong(1),
  "writeConcernMajorityJournalDefault" : true,
  "members" : [
    {
      "_id" : 0,
      "host" : "192.168.56.198:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 1,
      "tags" : {


      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 1,
      "host" : "192.168.56.199:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 1,
      "tags" : {


      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 2,
      "host" : "192.168.56.199:27018",
      "arbiterOnly" : true,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 0,
      "tags" : {


      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    }
  ],
  "settings" : {
    "chainingAllowed" : true,
    "heartbeatIntervalMillis" : 2000,
    "heartbeatTimeoutSecs" : 10,
    "electionTimeoutMillis" : 10000,
    "catchUpTimeoutMillis" : -1,
    "catchUpTakeoverDelayMillis" : 30000,
    "getLastErrorModes" : {


    },
    "getLastErrorDefaults" : {
      "w" : 1,
      "wtimeout" : 0
    },
    "replicaSetId" : ObjectId("61b86af0a21015e69623e18d")
  }
}

rs.status() 查看狀態信息。

test12:PRIMARY> rs.status()
{
  "set" : "test12",
  "date" : ISODate("2021-12-14T10:07:46.561Z"),
  "myState" : 1,
  "term" : NumberLong(1),
  "syncingTo" : "",
  "syncSourceHost" : "",
  "syncSourceId" : -1,
  "heartbeatIntervalMillis" : NumberLong(2000),
  "majorityVoteCount" : 2,
  "writeMajorityCount" : 2,
  "optimes" : {
    "lastCommittedOpTime" : {
      "ts" : Timestamp(1639476462, 1),
      "t" : NumberLong(1)
    },
    "lastCommittedWallTime" : ISODate("2021-12-14T10:07:42.560Z"),
    "readConcernMajorityOpTime" : {
      "ts" : Timestamp(1639476462, 1),
      "t" : NumberLong(1)
    },
    "readConcernMajorityWallTime" : ISODate("2021-12-14T10:07:42.560Z"),
    "appliedOpTime" : {
      "ts" : Timestamp(1639476462, 1),
      "t" : NumberLong(1)
    },
    "durableOpTime" : {
      "ts" : Timestamp(1639476462, 1),
      "t" : NumberLong(1)
    },
    "lastAppliedWallTime" : ISODate("2021-12-14T10:07:42.560Z"),
    "lastDurableWallTime" : ISODate("2021-12-14T10:07:42.560Z")
  },
  "lastStableRecoveryTimestamp" : Timestamp(1639476442, 1),
  "lastStableCheckpointTimestamp" : Timestamp(1639476442, 1),
  "electionCandidateMetrics" : {
    "lastElectionReason" : "electionTimeout",
    "lastElectionDate" : ISODate("2021-12-14T09:59:22.407Z"),
    "electionTerm" : NumberLong(1),
    "lastCommittedOpTimeAtElection" : {
      "ts" : Timestamp(0, 0),
      "t" : NumberLong(-1)
    },
    "lastSeenOpTimeAtElection" : {
      "ts" : Timestamp(1639475952, 1),
      "t" : NumberLong(-1)
    },
    "numVotesNeeded" : 2,
    "priorityAtElection" : 1,
    "electionTimeoutMillis" : NumberLong(10000),
    "numCatchUpOps" : NumberLong(0),
    "newTermStartDate" : ISODate("2021-12-14T09:59:22.431Z"),
    "wMajorityWriteAvailabilityDate" : ISODate("2021-12-14T09:59:23.493Z")
  },
  "members" : [
    {
      "_id" : 0,
      "name" : "192.168.56.198:27017",
      "health" : 1,
      "state" : 2,
      "stateStr" : "SECONDARY",
      "uptime" : 514,
      "optime" : {
        "ts" : Timestamp(1639476462, 1),
        "t" : NumberLong(1)
      },
      "optimeDurable" : {
        "ts" : Timestamp(1639476462, 1),
        "t" : NumberLong(1)
      },
      "optimeDate" : ISODate("2021-12-14T10:07:42Z"),
      "optimeDurableDate" : ISODate("2021-12-14T10:07:42Z"),
      "lastHeartbeat" : ISODate("2021-12-14T10:07:45.153Z"),
      "lastHeartbeatRecv" : ISODate("2021-12-14T10:07:46.542Z"),
      "pingMs" : NumberLong(1),
      "lastHeartbeatMessage" : "",
      "syncingTo" : "192.168.56.199:27017",
      "syncSourceHost" : "192.168.56.199:27017",
      "syncSourceId" : 1,
      "infoMessage" : "",
      "configVersion" : 1
    },
    {
      "_id" : 1,
      "name" : "192.168.56.199:27017",
      "health" : 1,
      "state" : 1,
      "stateStr" : "PRIMARY",
      "uptime" : 1001,
      "optime" : {
        "ts" : Timestamp(1639476462, 1),
        "t" : NumberLong(1)
      },
      "optimeDate" : ISODate("2021-12-14T10:07:42Z"),
      "syncingTo" : "",
      "syncSourceHost" : "",
      "syncSourceId" : -1,
      "infoMessage" : "",
      "electionTime" : Timestamp(1639475962, 1),
      "electionDate" : ISODate("2021-12-14T09:59:22Z"),
      "configVersion" : 1,
      "self" : true,
      "lastHeartbeatMessage" : ""
    },
    {
      "_id" : 2,
      "name" : "192.168.56.199:27018",
      "health" : 1,
      "state" : 7,
      "stateStr" : "ARBITER",
      "uptime" : 514,
      "lastHeartbeat" : ISODate("2021-12-14T10:07:44.896Z"),
      "lastHeartbeatRecv" : ISODate("2021-12-14T10:07:44.896Z"),
      "pingMs" : NumberLong(0),
      "lastHeartbeatMessage" : "",
      "syncingTo" : "",
      "syncSourceHost" : "",
      "syncSourceId" : -1,
      "infoMessage" : "",
      "configVersion" : 1
    }
  ],
  "ok" : 1,
  "$clusterTime" : {
    "clusterTime" : Timestamp(1639476462, 1),
    "signature" : {
      "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
      "keyId" : NumberLong(0)
    }
  },
  "operationTime" : Timestamp(1639476462, 1)
}

（3）將新節點添加至集群

在主庫上執行rs.add()將新節點添加進集群中.

生產環境添加節點時，建議將priority及votes設為0,即不會選為主（priority默認1），也沒有投票特性（votes默認1，有投票權）。

test12:PRIMARY> rs.add( { host: "192.168.56.197:27017", priority: 0, votes: 0 } )
{
  "ok" : 1,
  "$clusterTime" : {
    "clusterTime" : Timestamp(1639476997, 1),
    "signature" : {
      "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
      "keyId" : NumberLong(0)
    }
  },
  "operationTime" : Timestamp(1639476997, 1)
}

另外，生產環境是從主庫拉取全量數據，如果數據量較大，則需要觀察主庫的壓力及對線上業務的影響。

同步數據的過程中，新節點的狀態stateStr 為STARTUP2，待同步完成后會變為SECONDARY。

（4）重置新節點的屬性

此時再用rs.config()查看新節點狀態，priority及votes是之前設的0，可以使用 rs.recofig()命令進行調整

test12:PRIMARY> rs.config()
{
  "_id" : "test12",
  "version" : 2,
  "protocolVersion" : NumberLong(1),
  "writeConcernMajorityJournalDefault" : true,
  "members" : [
    {
      "_id" : 0,
      "host" : "192.168.56.198:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 1,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 1,
      "host" : "192.168.56.199:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 1,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 2,
      "host" : "192.168.56.199:27018",
      "arbiterOnly" : true,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 0,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 3,
      "host" : "192.168.56.197:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 0,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 0
    }
  ],
  "settings" : {
    "chainingAllowed" : true,
    "heartbeatIntervalMillis" : 2000,
    "heartbeatTimeoutSecs" : 10,
    "electionTimeoutMillis" : 10000,
    "catchUpTimeoutMillis" : -1,
    "catchUpTakeoverDelayMillis" : 30000,
    "getLastErrorModes" : {
      
    },
    "getLastErrorDefaults" : {
      "w" : 1,
      "wtimeout" : 0
    },
    "replicaSetId" : ObjectId("61b86af0a21015e69623e18d")
  }
}

從上面可以看到新節點的id為3 ，則可以通過如下命令調整對應的屬性。

var cfg = rs.conf()
cfg.members[3].priority = 1
cfg.members[3].votes = 1
rs.reconfig(cfg)

調整后再查看，屬性已調整。

test12:PRIMARY> rs.config()
{
  "_id" : "test12",
  "version" : 3,
  "protocolVersion" : NumberLong(1),
  "writeConcernMajorityJournalDefault" : true,
  "members" : [
    {
      "_id" : 0,
      "host" : "192.168.56.198:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 1,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 1,
      "host" : "192.168.56.199:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 1,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 2,
      "host" : "192.168.56.199:27018",
      "arbiterOnly" : true,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 0,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    },
    {
      "_id" : 3,
      "host" : "192.168.56.197:27017",
      "arbiterOnly" : false,
      "buildIndexes" : true,
      "hidden" : false,
      "priority" : 1,
      "tags" : {
        
      },
      "slaveDelay" : NumberLong(0),
      "votes" : 1
    }
  ],
  "settings" : {
    "chainingAllowed" : true,
    "heartbeatIntervalMillis" : 2000,
    "heartbeatTimeoutSecs" : 10,
    "electionTimeoutMillis" : 10000,
    "catchUpTimeoutMillis" : -1,
    "catchUpTakeoverDelayMillis" : 30000,
    "getLastErrorModes" : {
      
    },
    "getLastErrorDefaults" : {
      "w" : 1,
      "wtimeout" : 0
    },
    "replicaSetId" : ObjectId("61b86af0a21015e69623e18d")
  }
}

至此，新節點便加入了副本集中。

3、注意點總結

一個副本集，最多可以擁有50個secondary，最多可以有7個投票成員，在副本集里面添加一個新成員，如果之前副本集已經有了7個成員，那么可以設置成非投票成員，或者你從移除之前一個投票成員出來。
新節點的版本、配置建議與原集群一致。
注意添加新節點前確定網絡互通。
如果集群數據量較大，則選擇業務低峰期添加節點，并觀察壓力情況。
新節點加入時建議將priority及votes設為0。

責任編輯：姜華來源：今日頭條

Mongodb 副本集架構