MongoDB单节点转换成复制集

背景

之前图省事，开发环境几台mongodb都是单机在运行，考虑到宕机等不确定的风险，给他们做一下高可用。mongodb原生的复制集方案非常简单好用。

操作步骤

• MongoDB版本： 3.6.21
• 实验环境中，3个mongodb实例运行在同一个虚拟机上。另外，从节约资源考虑，我们最终搭建完的结构是： 1主、1备、1仲裁节点
• 实验环境
  • 当前正在运行的单机节点：10.0.3.115:27018
  • 准备添加secondary节点：10.0.3.115:27019
  • 准备添加arbiter节点：10.0.3.115:27020

1.关闭当前的 27018 节点

> use admin
> db.shutdownServer()

2.修改配置文件

修改 27018 的配置文件（YAML格式），在最后加上下面3行内容

replication:
  oplogSizeMB: 2048
  replSetName: maotiapp

3.再次启动 27018 进程

mongod -f /data/mongodb/27018/conf/mongod.conf

4.初始化集群配置

mongo --port 27018

> 
> config = {_id:'maotiapp', members:[{_id:0,host:'10.0.3.115:27018'}]}
{
	"_id" : "maotiapp",
	"members" : [
		{
			"_id" : 0,
			"host" : "10.0.3.115:27018"
		}
	]
}



> rs.initiate(config)
{ "ok" : 1 }



maotiapp:PRIMARY> rs.status()
{
	"set" : "maotiapp",
	"date" : ISODate("2021-01-18T09:52:34.567Z"),
	"myState" : 1,
	"term" : NumberLong(1),
	"syncingTo" : "",
	"syncSourceHost" : "",
	"syncSourceId" : -1,
	"heartbeatIntervalMillis" : NumberLong(2000),
	"optimes" : {
		"lastCommittedOpTime" : {
			"ts" : Timestamp(1610963543, 7),
			"t" : NumberLong(1)
		},
		"readConcernMajorityOpTime" : {
			"ts" : Timestamp(1610963543, 7),
			"t" : NumberLong(1)
		},
		"appliedOpTime" : {
			"ts" : Timestamp(1610963543, 7),
			"t" : NumberLong(1)
		},
		"durableOpTime" : {
			"ts" : Timestamp(1610963543, 7),
			"t" : NumberLong(1)
		}
	},
	"members" : [
		{
			"_id" : 0,
			"name" : "10.0.3.115:27018",
			"health" : 1,
			"state" : 1,
			"stateStr" : "PRIMARY",
			"uptime" : 171,
			"optime" : {
				"ts" : Timestamp(1610963543, 7),
				"t" : NumberLong(1)
			},
			"optimeDate" : ISODate("2021-01-18T09:52:23Z"),
			"syncingTo" : "",
			"syncSourceHost" : "",
			"syncSourceId" : -1,
			"infoMessage" : "could not find member to sync from",
			"electionTime" : Timestamp(1610963541, 2),
			"electionDate" : ISODate("2021-01-18T09:52:21Z"),
			"configVersion" : 1,
			"self" : true,
			"lastHeartbeatMessage" : ""
		}
	],
	"ok" : 1,
	"operationTime" : Timestamp(1610963543, 7),
	"$clusterTime" : {
		"clusterTime" : Timestamp(1610963543, 7),
		"signature" : {
			"hash" : BinData(0,"NQlkxnscuDDzaRztIGdHu5yA3AY="),
			"keyId" : NumberLong("6919035732233289729")
		}
	}
}

5.启动 27019 27020 实例

修改 27019 27020 配置文件与 27018 一致

启动服务

mongod -f /data/mongodb/27019/conf/mongod.conf
mongod -f /data/mongodb/27020/conf/mongod.conf

6.登录到 27018 实例里，将 27019 27020 加到集群中去

maotiapp:PRIMARY> rs.add('10.0.3.115:27019')
maotiapp:PRIMARY> rs.addArb('10.0.3.115:27020')

7. 查看集群状态

maotiapp:PRIMARY> rs.isMaster()
{
	"hosts" : [
		"10.0.3.115:27018",
		"10.0.3.115:27019"
	],
	"arbiters" : [
		"10.0.3.115:27020"
	],
	"setName" : "maotiapp",
	"setVersion" : 3,
	"ismaster" : true,
	"secondary" : false,
	"primary" : "10.0.3.115:27018",
	"me" : "10.0.3.115:27018",
	"electionId" : ObjectId("7fffffff0000000000000001"),
	"lastWrite" : {
		"opTime" : {
			"ts" : Timestamp(1610966883, 1),
			"t" : NumberLong(1)
		},
		"lastWriteDate" : ISODate("2021-01-18T10:48:03Z"),
		"majorityOpTime" : {
			"ts" : Timestamp(1610966883, 1),
			"t" : NumberLong(1)
		},
		"majorityWriteDate" : ISODate("2021-01-18T10:48:03Z")
	},
	"maxBsonObjectSize" : 16777216,
	"maxMessageSizeBytes" : 48000000,
	"maxWriteBatchSize" : 100000,
	"localTime" : ISODate("2021-01-18T10:48:06.939Z"),
	"logicalSessionTimeoutMinutes" : 30,
	"minWireVersion" : 0,
	"maxWireVersion" : 6,
	"readOnly" : false,
	"ok" : 1,
	"operationTime" : Timestamp(1610966883, 1),
	"$clusterTime" : {
		"clusterTime" : Timestamp(1610966883, 1),
		"signature" : {
			"hash" : BinData(0,"iiPbfyjfCmCW/Uai55twlPRmg+U="),
			"keyId" : NumberLong("6919035732233289729")
		}
	}
}


maotiapp:PRIMARY> rs.status()
maotiapp:PRIMARY> rs.conf()

如果有数据正在同步过程中，这里可能看到新加的节点是startup或者其它的状态，稍等即可。

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