【Mongodb】如何建立mongodb的replica set

楊奇龍發表於2011-10-31
Replica sets 在主從複製上做的擴充套件,增加了故障自動切換和自動修復成員節點。下面從技術上介紹如何搭建mongodb的replica set (個人覺得,搭建mongodb本身沒有多少乾貨,重要是如何災難規劃)
1 建立複製叢集節點的資料存放目錄
mkdir -p /opt/mongodata/r1
mkdir -p /opt/mongodata/r2
mkdir -p /opt/mongodata/r3
2 在三個視窗分別執行如下命令:
./mongod --dbpath /opt/mongodata/r1 --port 27018  --rest --replSet myset
./mongod --dbpath /opt/mongodata/r2 --port 27019  --rest --replSet myset
./mongod --dbpath /opt/mongodata/r3 --port 27020  --rest --replSet myset
3 在第四個視窗執行如下命令:
[mongodb@rac4 bin]$ ./mongo 127.0.0.1:27018 init.js
MongoDB shell version: 2.0.1
connecting to: 127.0.0.1:27018/test
init.js 內容如下:
[mongodb@rac4 bin]$ cat init.js 
rs.initiate({
    _id : "myset",
    members : [
        {_id : 0, host : "10.250.7.220:27018"},
        {_id : 1, host : "10.250.7.220:27019"},
        {_id : 2, host : "10.250.7.220:27020"}
    ]
})
啟動3個服務節點,從log日誌可以看到,三個節點相互協商,選擇埠為27018的一個節點作為Primary,另外兩個自動作為Secondary節點。
Mon Oct 31 20:27:53 [conn2] replSet info saving a newer config version to local.system.replset
Mon Oct 31 20:27:53 [conn2] replSet saveConfigLocally done
Mon Oct 31 20:27:53 [conn2] replSet replSetInitiate config now saved locally.  Should come online in about a minute.
Mon Oct 31 20:27:53 [conn2] command admin.$cmd command: { replSetInitiate: { _id: "myset", members: [ { _id: 0.0, host: "10.250.7.220:27018" }, { _id: 1.0, host: "10.250.7.220:27019" }, { _id: 2.0, host: "10.250.7.220:27020" } ] } } ntoreturn:1 reslen:112 12095ms
Mon Oct 31 20:27:53 [conn2] end connection 127.0.0.1:15252
Mon Oct 31 20:27:53 [rsStart] replSet STARTUP2
Mon Oct 31 20:27:53 [rsHealthPoll] replSet info 10.250.7.220:27019 is down (or slow to respond): still initializing
Mon Oct 31 20:27:53 [rsHealthPoll] replSet member 10.250.7.220:27019 is now in state DOWN
Mon Oct 31 20:27:53 [rsHealthPoll] replSet info 10.250.7.220:27020 is down (or slow to respond): still initializing
Mon Oct 31 20:27:53 [rsHealthPoll] replSet member 10.250.7.220:27020 is now in state DOWN
Mon Oct 31 20:27:53 [rsSync] replSet SECONDARY
Mon Oct 31 20:27:55 [initandlisten] connection accepted from 10.250.7.220:44134 #3
Mon Oct 31 20:27:59 [rsHealthPoll] replSet info member 10.250.7.220:27019 is up
Mon Oct 31 20:27:59 [rsHealthPoll] replSet member 10.250.7.220:27019 is now in state STARTUP2
Mon Oct 31 20:27:59 [rsMgr] not electing self, 10.250.7.220:27019 would veto
Mon Oct 31 20:28:01 [initandlisten] connection accepted from 10.250.7.220:44137 #4
Mon Oct 31 20:28:05 [rsMgr] replSet info electSelf 0
Mon Oct 31 20:28:05 [rsMgr] replSet PRIMARY
Mon Oct 31 20:28:07 [rsHealthPoll] replSet member 10.250.7.220:27019 is now in state RECOVERING
Mon Oct 31 20:28:10 [initandlisten] connection accepted from 10.250.7.220:44141 #5
Mon Oct 31 20:28:10 [initandlisten] connection accepted from 10.250.7.220:44142 #6
Mon Oct 31 20:28:11 [slaveTracking] build index local.slaves { _id: 1 }
Mon Oct 31 20:28:11 [slaveTracking] build index done 0 records 0.001 secs
Mon Oct 31 20:28:13 [rsHealthPoll] replSet info member 10.250.7.220:27020 is up
Mon Oct 31 20:28:13 [rsHealthPoll] replSet member 10.250.7.220:27020 is now in state STARTUP2
Mon Oct 31 20:28:14 [conn6] end connection 10.250.7.220:44142
Mon Oct 31 20:28:14 [conn5] end connection 10.250.7.220:44141
Mon Oct 31 20:28:15 [initandlisten] connection accepted from 10.250.7.220:44144 #7
Mon Oct 31 20:28:15 [rsHealthPoll] replSet member 10.250.7.220:27019 is now in state SECONDARY
Mon Oct 31 20:28:15 [rsHealthPoll] replSet member 10.250.7.220:27020 is now in state RECOVERING
Mon Oct 31 20:28:28 [initandlisten] connection accepted from 127.0.0.1:59232 #8
從客戶端進入資料庫:
[mongodb@rac4 bin]$ ./mongo 127.0.0.1:27018
MongoDB shell version: 2.0.1
connecting to: 127.0.0.1:27018/test
PRIMARY> rs.status()  --檢視replica set狀態的命令
{
        "set" : "myset",
        "date" : ISODate("2011-10-31T12:29:17Z"),
        "myState" : 1,
        "members" : [
                {
                        "_id" : 0,
                        "name" : "10.250.7.220:27018",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "optime" : {
                                "t" : 1320064073000,
                                "i" : 1
                        },
                        "optimeDate" : ISODate("2011-10-31T12:27:53Z"),
                        "self" : true
                },
                {
                        "_id" : 1,
                        "name" : "10.250.7.220:27019",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 78,
                        "optime" : {
                                "t" : 1320064073000,
                                "i" : 1
                        },
                        "optimeDate" : ISODate("2011-10-31T12:27:53Z"),
                        "lastHeartbeat" : ISODate("2011-10-31T12:29:16Z"),
                        "pingMs" : 0
                },
                {
                        "_id" : 2,
                        "name" : "10.250.7.220:27020",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 64,
                        "optime" : {
                                "t" : 1320064073000,
                                "i" : 1
                        },
                        "optimeDate" : ISODate("2011-10-31T12:27:53Z"),
                        "lastHeartbeat" : ISODate("2011-10-31T12:29:16Z"),
                        "pingMs" : 1
                }
        ],
        "ok" : 1
}
狀態中關鍵資料位
state:1表示該host是當前可以進行讀寫,2:不能讀寫
health:1表示該host目前是正常的,0:異常
下面會進行從庫的讀測試,會出現error: { "$err" : "not master and slaveok=false", "code" : 13435 }
PRIMARY> rs.conf() --檢視replica set配置的命令
{
        "_id" : "myset",
        "version" : 1,
        "members" : [
                {
                        "_id" : 0,
                        "host" : "10.250.7.220:27018"
                },
                {
                        "_id" : 1,
                        "host" : "10.250.7.220:27019"
                },
                {
                        "_id" : 2,
                        "host" : "10.250.7.220:27020"
                }
        ]
}
PRIMARY> db.isMaster();--檢視是否是主庫的命令,當然可以從提示符中看出primary
{
        "setName" : "myset",
        "ismaster" : true,  ##是primary
        "secondary" : false,
        "hosts" : [
                "10.250.7.220:27018",
                "10.250.7.220:27020",
                "10.250.7.220:27019"
        ],
        "primary" : "10.250.7.220:27018",
        "me" : "10.250.7.220:27018",
        "maxBsonObjectSize" : 16777216,
        "ok" : 1
}
分別登入其他兩個mongodb 服務:
[mongodb@rac4 bin]$ ./mongo 127.0.0.1:27019
MongoDB shell version: 2.0.1
connecting to: 127.0.0.1:27019/test
SECONDARY> 
SECONDARY> 
SECONDARY> db.isMaster();
{
        "setName" : "myset",
        "ismaster" : false,
        "secondary" : true,
        "hosts" : [
                "10.250.7.220:27019",
                "10.250.7.220:27020",
                "10.250.7.220:27018"
        ],
        "primary" : "10.250.7.220:27018",
        "me" : "10.250.7.220:27019",
        "maxBsonObjectSize" : 16777216,
        "ok" : 1
}
SECONDARY>
[mongodb@rac4 bin]$ ./mongo 127.0.0.1:27020
MongoDB shell version: 2.0.1
connecting to: 127.0.0.1:27020/test
SECONDARY> 
SECONDARY> db.isMaster();
{
        "setName" : "myset",
        "ismaster" : false,
        "secondary" : true,
        "hosts" : [
                "10.250.7.220:27020",
                "10.250.7.220:27019",
                "10.250.7.220:27018"
        ],
        "primary" : "10.250.7.220:27018",
        "me" : "10.250.7.220:27020",
        "maxBsonObjectSize" : 16777216,
        "ok" : 1
至此搭建成功。。
對主庫進行寫操作,從庫檢視:
[mongodb@rac4 bin]$ ./mongo 127.0.0.1:27020
MongoDB shell version: 2.0.1
connecting to: 127.0.0.1:27020/test
PRIMARY> use test
switched to db test
PRIMARY> 
PRIMARY> db.yql.insert({val:"this is a message on 27020 primary !"});
PRIMARY> 
主庫日誌:
Mon Oct 31 21:03:46 [FileAllocator] allocating new datafile /opt/mongodata/r3/test.ns, filling with zeroes...
Mon Oct 31 21:03:46 [FileAllocator] done allocating datafile /opt/mongodata/r3/test.ns, size: 16MB,  took 0.256 secs
Mon Oct 31 21:03:46 [FileAllocator] allocating new datafile /opt/mongodata/r3/test.0, filling with zeroes...
Mon Oct 31 21:03:48 [clientcursormon] mem (MB) res:35 virt:2726 mapped:1248
Mon Oct 31 21:03:50 [FileAllocator] done allocating datafile /opt/mongodata/r3/test.0, size: 64MB,  took 4.488 secs
Mon Oct 31 21:03:50 [conn6] build index test.yql { _id: 1 }
Mon Oct 31 21:03:50 [conn6] build index done 0 records 0 secs
Mon Oct 31 21:03:50 [conn6] insert test.yql 4759ms
Mon Oct 31 21:03:50 [FileAllocator] allocating new datafile /opt/mongodata/r3/test.1, filling with zeroes...
Mon Oct 31 21:03:51 [conn8] getmore local.oplog.rs query: { ts: { $gte: new Date(5669632022159556609) } } cursorid:6257712144272734285 nreturned:1 reslen:146 5031ms
Mon Oct 31 21:03:51 [conn5] getmore local.oplog.rs query: { ts: { $gte: new Date(5669632022159556609) } } cursorid:423878080662643430 nreturned:1 reslen:146 5631ms
Mon Oct 31 21:03:54 [FileAllocator] done allocating datafile /opt/mongodata/r3/test.1, size: 128MB,  took 3.818 secs
從庫日誌,可以看出 從庫從主庫應用日誌,複製資料檔案的過程。
Mon Oct 31 20:49:27 [clientcursormon] mem (MB) res:19 virt:2693 mapped:1232
Mon Oct 31 20:54:27 [clientcursormon] mem (MB) res:19 virt:2693 mapped:1232
Mon Oct 31 20:59:27 [clientcursormon] mem (MB) res:19 virt:2693 mapped:1232
Mon Oct 31 21:03:51 [FileAllocator] allocating new datafile /opt/mongodata/r2/test.ns, filling with zeroes...
Mon Oct 31 21:03:54 [FileAllocator] done allocating datafile /opt/mongodata/r2/test.ns, size: 16MB,  took 3.396 secs
Mon Oct 31 21:03:54 [FileAllocator] allocating new datafile /opt/mongodata/r2/test.0, filling with zeroes...
Mon Oct 31 21:04:00 [FileAllocator] done allocating datafile /opt/mongodata/r2/test.0, size: 64MB,  took 5.79 secs
Mon Oct 31 21:04:00 [rsSync] build index test.yql { _id: 1 }
Mon Oct 31 21:04:00 [rsSync] build index done 0 records 0 secs
Mon Oct 31 21:04:00 [FileAllocator] allocating new datafile /opt/mongodata/r2/test.1, filling with zeroes...
Mon Oct 31 21:04:03 [FileAllocator] done allocating datafile /opt/mongodata/r2/test.1, size: 128MB,  took 2.965 secs
Mon Oct 31 21:04:37 [clientcursormon] mem (MB) res:17 virt:2853 mapped:1312
Mon Oct 31 21:04:41 [conn6] end connection 127.0.0.1:44672
如前面介紹rs.status()時所說,state:1表示該host是當前可以進行讀寫,2:不能讀寫
{
  "_id" : 1,
  "name" : "10.250.7.220:27019",
  "health" : 1,
  "state" : 2,  -- 從庫的state為 2 ,此時是不可讀寫的。
  "stateStr" : "SECONDARY",
  "uptime" : 78,
  "optime" : {
  "t" : 1320064073000,
  "i" : 1
 },
 在從庫進行讀操作,會報錯。
[mongodb@rac4 bin]$ ./mongo 127.0.0.1:27019
MongoDB shell version: 2.0.1
connecting to: 127.0.0.1:27019/test
SECONDARY> use test
switched to db test
SECONDARY> db.yql.find();
error: { "$err" : "not master and slaveok=false", "code" : 13435 }

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