MongoDB 高可用可用分兩種:
Master-Slave 主從複製：：
只需要在某一個服務啟動時加上–master 引數，而另一個服務加上–slave 與–source 引數，
即可實現同步。 MongoDB 的最新版本已不再推薦此方案。
Replica Sets 複製集：：
MongoDB 在 1.6 版本對開發了新功能 replica set，這比之前的 replication 功能要強大一
些，增加了故障自動切換和自動修復成員節點，各個 DB 之間資料完全一致，大大降低了維
護成功。 auto shard 已經明確說明不支援 replication paris，建議使用 replica set， replica set
故障切換完全自動。

1、建立資料檔案儲存路徑

[root@localhost ~]# mkdir -p /data/data/r0
[root@localhost ~]# mkdir -p /data/data/r1
[root@localhost ~]# mkdir -p /data/data/r2

2、建立日誌檔案路徑

[root@localhost ~]# mkdir -p /data/log

3、建立主從 key 檔案，用於標識叢集的私鑰的完整路徑，如果各個例項的 key file 內容不一
致，程式將不能正常用。

[root@localhost ~]# mkdir -p /data/key
[root@localhost ~]# echo "this is rs1 super secret key" > /data/key/r0
[root@localhost ~]# echo "this is rs1 super secret key" > /data/key/r1
[root@localhost ~]# echo "this is rs1 super secret key" > /data/key/r2
[root@localhost ~]# chmod 600 /data/key/r*

4、啟動 3 個例項

[root@localhost ~]# /Apps/mongo/bin/mongod --replSet rs1 --keyFile /data/key/r0 --fork --port
28010 --dbpath /data/data/r0 --logpath=/data/log/r0.log --logappend
all output going to: /data/log/r0.log
forked process: 6573
[root@localhost ~]# /Apps/mongo/bin/mongod --replSet rs1 --keyFile /data/key/r1 --fork --port
28011 --dbpath /data/data/r1 --logpath=/data/log/r1.log --logappend
all output going to: /data/log/r1.log
forked process: 6580
[root@localhost ~]# /Apps/mongo/bin/mongod --replSet rs1 --keyFile /data/key/r2 --fork --port
28012 --dbpath /data/data/r2 --logpath=/data/log/r2.log --logappend
all output going to: /data/log/r2.log
forked process: 6585

5、配置及初始化 Replica Sets

[root@localhost bin]# /Apps/mongo/bin/mongo -port 28010
MongoDB shell version: 1.8.1
connecting to: 127.0.0.1:28010/test
> config_rs1 = {_id: 'rs1', members: [
... {_id: 0, host: 'localhost:28010', priority:1}, --成員 IP 及埠,最好是寫ip那樣就可以跨機器， priority=1 指 PRIMARY
... {_id: 1, host: 'localhost:28011'},
... {_id: 2, host: 'localhost:28012'}]
... }
{
"_id" : "rs1",
"members" : [
{
"_id" : 0,
"host" : "localhost:28010"
},
{
"_id" : 1,
"host" : "localhost:28011"
},
{
"_id" : 2,
"host" : "localhost:28012"
}
]
}
> rs.initiate(config_rs1); --初始化配置
{
"info" : "Config now saved locally. Should come online in about a minute.",
"ok" : 1
}

6檢視複製集狀態
> rs.status()

{
"set" : "rs1",
"date" : ISODate("2012-05-31T09:49:57Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "localhost:28010",
"health" : 1, --1 表明正常; 0 表明異常
"state" : 1, -- 1 表明是 Primary; 2 表明是 Secondary;
"stateStr" : "PRIMARY", --表明此機器是主庫
"optime" : {
"t" : 1338457763000,
"i" : 1
},
"optimeDate" : ISODate("2012-05-31T09:49:23Z"),
"self" : true
},
{
"_id" : 1,
"name" : "localhost:28011",
"health" : 1,
65 / 91
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 23,
"optime" : {
"t" : 1338457763000,
"i" : 1
},
"optimeDate" : ISODate("2012-05-31T09:49:23Z"),
"lastHeartbeat" : ISODate("2012-05-31T09:49:56Z")
},
{
"_id" : 2,
"name" : "localhost:28012",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 23,
"optime" : {
"t" : 1338457763000,
"i" : 1
},
"optimeDate" : ISODate("2012-05-31T09:49:23Z"),
"lastHeartbeat" : ISODate("2012-05-31T09:49:56Z")
}
],
"ok" : 1
}

還可以用 isMaster 檢視 Replica Sets 狀態。

rs1:PRIMARY> rs.isMaster()
{
"setName" : "rs1",
"ismaster" : true,
"secondary" : false,
"hosts" : [
"localhost:28010",
"localhost:28012",
"localhost:28011"
],
"maxBsonObjectSize" : 16777216,
"ok" : 1
}

rs1:PRIMARY>rs.conf()
shard1:SECONDARY> use local
switched to db local
shard1:SECONDARY> db.system.replset.find()

Replica sets複製集的搭建

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