原文鏈接：https://blog.csdn.net/jacobxian/article/details/103634866
在mongodb副本集集羣中,若是丟失了n/2+1個節點,也就是失去了多數節點時候,在集羣內無法投票表決剩下的節點誰能當主庫,那就需要強制其中一個節點爲主庫.
下面是操作步驟:
1.執行cfg=rs.conf()
2.需要設置需要的_id爲主庫，
cfg.members=[cfg.members[3]]
3.執行集羣重新設置
4.rs.reconfig(cfg, {force: true});
5.rs.status()
下面是詳細操作步驟,該集羣是四個節點的副本集,其中三個節點已經丟失,使剩下的節點爲主節點,單實例運行.
執行cfg=rs.conf(),獲取集羣的節點信息:
cms:SECONDARY> cfg=rs.conf()
{
"_id" : "cms",
"version" : 32948,
"protocolVersion" : NumberLong(1),
"members" : [
{
"_id" : 0,
"host" : "192.168.1.193:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 1,
"host" : "192.168.1.195:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 2,
"host" : "192.168.1.198:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 3,
"host" : "192.168.1.199:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
}
],
"settings" : {
"chainingAllowed" : true,
"heartbeatIntervalMillis" : 2000,
"heartbeatTimeoutSecs" : 10,
"electionTimeoutMillis" : 10000,
"getLastErrorModes" : {
},
"getLastErrorDefaults" : {
"w" : 1,
"wtimeout" : 0
},
"replicaSetId" : ObjectId("59cab0d69b86b9e815cfc02b")
}
}
下面指定199爲主節點
cms:SECONDARY> cfg.members=[cfg.members[3]]
[
{
"_id" : 3,
"host" : "192.168.1.199:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
}
]
cms:SECONDARY> rs.reconfig(cfg, {force: true})
{ "ok" : 1 }
查看更改後的集羣狀態,操作完成,變成了單實例節點.然後通過添加從節點來實現副本集
cms:SECONDARY> rs.status()
{
"set" : "cms",
"date" : ISODate("2018-09-04T01:54:12.445Z"),
"myState" : 1,
"term" : NumberLong(6),
"heartbeatIntervalMillis" : NumberLong(2000),
"members" : [
{
"_id" : 3,
"name" : "192.168.1.199:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 3152420,
"optime" : {
"ts" : Timestamp(1536026052, 24),
"t" : NumberLong(6)
},
"optimeDate" : ISODate("2018-09-04T01:54:12Z"),
"infoMessage" : "could not find member to sync from",
"electionTime" : Timestamp(1536026047, 1),
"electionDate" : ISODate("2018-09-04T01:54:07Z"),
"configVersion" : 137682,
"self" : true
}
],
"ok" : 1
}
添加新的節點:
config = { _id:"cms", members:
[
{_id:0,host:"192.168.1.193:27017"},
{_id:1,host:"192.168.1.194:27017"},
{_id:2,host:"192.168.1.198:27017"},
{_id:3,host:"192.168.1.199:27017"}
]
}
rs.reconfig(config);
然後在新節點啓動mongod進程,必須要把新節點數據文件清空.
節點啓動以後,會自動拉取主庫數據,然後創建索引.
mongod --fork --config /data0/mongodb/mongod.conf