【Mongodb】如何创建mongodb的replica set

Replica sets 在主从复制上做的扩展，增加了故障自动切换和自动修复成员节点。下面从技术上介绍如何搭建mongodb的replica set (个人觉得，搭建mongodb本身没有多少干货，重要是如何灾难规划)

1 建立复制集群节点的数据存放目录

mkdir -p /opt/mongodata/r1

mkdir -p /opt/mongodata/r2

mkdir -p /opt/mongodata/r3

2 在三个窗口分别执行如下命令：

./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 在第四个窗口执行如下命令：

[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 内容如下：

[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"}

    ]

})

启动3个服务节点，从log日志可以看到，三个节点相互协商，选择端口为27018的一个节点作为Primary，另外两个自动作为Secondary节点。

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

从客户端进入数据库：

[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()  --查看replica set状态的命令

{

        "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

}

状态中关键数据位

state：1表示该host是当前可以进行读写，2：不能读写

health：1表示该host目前是正常的，0:异常

下面会进行从库的读测试，会出现error: { "$err" : "not master and slaveok=false", "code" : 13435 }

PRIMARY> rs.conf() --查看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();--查看是否是主库的命令，当然可以从提示符中看出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

}

分别登录其他两个mongodb 服务：

[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。。

对主库进行写操作，从库查看：

[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> 

主库日志：

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

从库日志，可以看出 从库从主库应用日志，复制数据文件的过程。

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

如前面介绍rs.status()时所说，state：1表示该host是当前可以进行读写，2：不能读写

{

  "_id" : 1,

  "name" : "10.250.7.220:27019",

  "health" : 1,

  "state" : 2,  -- 从库的state为 2 ，此时是不可读写的。

  "stateStr" : "SECONDARY",

  "uptime" : 78,

  "optime" : {

  "t" : 1320064073000,

  "i" : 1

 },

 在从库进行读操作，会报错。

[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 }