#头条创作挑战赛#

mongodb副本集架构运行一段时间后如果业务发展需要新增新的成员，或者迁移集群，则可以参考本文处理

1. 准备工作

有一套mongodb 副本集的集群，部署方式参考 mongodb 4.0副本集搭建

准备一个新节点，使用和原副本集版本一致的mongodb

拷贝原副本集中的配置文件、keyfile文件，并注意修改keyfile文件的权限（600）

节点

角色

192.168.56.199:27017

PRIMARY

192.168.56.198:27018

SECONDARY

192.168.56.199:27018

ARBITER

准备加入的新节点： 192.168.56.197:27017

2. 添加节点

2.1 启动新节点

例如，原节点的版本是4.2.8，新节点版本一致，路径一致，然后启动新节点

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

2.2 主库上查看当前节点及配置信息

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() 查看状态信息

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)}

2.3 将新节点添加至集群

在主库上执行rs.add()将新节点添加进集群中

生产环境添加节点时，建议将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）

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，生产环境是从主库拉取全量数据，如果数据量较大，则需要观察主库的压力及对线上业务的影响。

同步数据的过程中，新节点的状态stateStr 为STARTUP2，待同步完成后会变为SECONDARY。

2.4 重置新节点的属性

此时再用rs.config()查看新节点状态，priority及votes是之前设的0，可以使用 rs.recofig()命令进行调整

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")  }}

从上面可以看到新节点的id为3 ，则可以通过如下命令调整对应的属性

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

调整后再查看，属性已调整

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，新节点便加入了副本集中

3. 注意点总结

一个副本集，最多可以拥有50个secondary，最多可以有7个投票成员，在副本集里面添加一个新成员，如果之前副本集已经有了7个成员，那么可以设置成非投票成员，或者你从移除之前一个投票成员出来新节点的版本、配置建议与原集群一致注意添加新节点前确定网络互通如果集群数据量较大，则选择业务低峰期添加节点，并观察压力情况新节点加入时建议将priority及votes设为0