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分类: Mysql/postgreSQL

21.4.3增减节点

MongoDB Replica Sets不仅提供高可用性的解决方案,它也同时提供负载均衡的解决方案,增减Replica Sets节点在实际应用中非常普遍,例如当应用的读压力暴增时,3台节点的环境已不能满足需求,那么就需要增加一些节点将压力平均分配一下;当应用的压力小时,可以减少一些节点来减少硬件资源的成本;总之这是一个长期且持续的工作。

21.4.3.1 增加节点

官方给我们提了2个方案用于增加节点,一种是通过oplog来增加节点,一种是通过数据库快照(--fastsync)和oplog来增加节点,下面将分别介绍。

21.4.3.1.1 通过oplog增加节点

①、配置并启动新节点,启用28013这个端口给新的节点

[root@localhost ~]# mkdir -p /data/data/r3

[root@localhost ~]# echo "this is rs1 super secret key" > /data/key/r3

[root@localhost ~]# chmod 600 /data/key/r3

[root@localhost ~]# /Apps/mongo/bin/mongod --replSet rs1 --keyFile /data/key/r3 --fork --port 28013 --dbpath /data/data/r3 --logpath=/data/log/r3.log --logappend

all output going to: /data/log/r3.log

forked process: 10553

[root@localhost ~]#

 

②、添加此新节点到现有的Replica Sets

rs1:PRIMARY> rs.add("localhost:28013")

{ "ok" : 1 }

 

③、查看Replica Sets我们可以清晰的看到内部是如何添加28013这个新节点的.

步骤一: 进行初始化

rs1: PRIMARY > rs.status()

{

        "set" : "rs1",

        "date" : ISODate("2012-05-31T12:17:44Z"),

        "myState" : 1,

        "members" : [

……

                {

                        "_id" : 3,

                        "name" : "localhost:28013",

                        "health" : 0,

                        "state" : 6,

                        "stateStr" : "(not reachable/healthy)",

                        "uptime" : 0,

                        "optime" : {

                                "t" : 0,

                                "i" : 0

                        },

                        "optimeDate" : ISODate("1970-01-01T00:00:00Z"),

                        "lastHeartbeat" : ISODate("2012-05-31T12:17:43Z"),

                        "errmsg" : "still initializing"

                }

        ],

        "ok" : 1

}

 

步骤二: 进行数据同步

rs1:PRIMARY> rs.status()

{

        "set" : "rs1",

        "date" : ISODate("2012-05-31T12:18:07Z"),

        "myState" : 1,

        "members" : [

……

                {

                        "_id" : 3,

                        "name" : "localhost:28013",

                        "health" : 1,

                        "state" : 3,

                        "stateStr" : "RECOVERING",

                        "uptime" : 16,

                        "optime" : {

                                "t" : 0,

                                "i" : 0

                        },

                        "optimeDate" : ISODate("1970-01-01T00:00:00Z"),

                        "lastHeartbeat" : ISODate("2012-05-31T12:18:05Z"),

                        "errmsg" : "initial sync need a member to be primary or secondary to do our initial sync"

                }

        ],

        "ok" : 1

}

 

步骤三: 初始化同步完成

rs1:PRIMARY> rs.status()

{

        "set" : "rs1",

        "date" : ISODate("2012-05-31T12:18:08Z"),

        "myState" : 1,

        "members" : [

……

                {

                        "_id" : 3,

                        "name" : "localhost:28013",

                        "health" : 1,

                        "state" : 3,

                        "stateStr" : "RECOVERING",

                        "uptime" : 17,

                        "optime" : {

                                "t" : 1338466661000,

                                "i" : 1

                        },

                        "optimeDate" : ISODate("2012-05-31T12:17:41Z"),

                        "lastHeartbeat" : ISODate("2012-05-31T12:18:07Z"),

                        "errmsg" : "initial sync done"

                }

        ],

        "ok" : 1

}

 

步骤四: 节点添加完成,状态正常

rs1:PRIMARY> rs.status()

{

        "set" : "rs1",

        "date" : ISODate("2012-05-31T12:18:10Z"),

        "myState" : 1,

        "members" : [

……

                {

                        "_id" : 3,

                        "name" : "localhost:28013",

                        "health" : 1,

                        "state" : 2,

                        "stateStr" : "SECONDARY",

                        "uptime" : 19,

                        "optime" : {

                                "t" : 1338466661000,

                                "i" : 1

                        },

                        "optimeDate" : ISODate("2012-05-31T12:17:41Z"),

                        "lastHeartbeat" : ISODate("2012-05-31T12:18:09Z")

                }

        ],

        "ok" : 1

}

 

④、验证数据已经同步过来了

[root@localhost data]# /Apps/mongo/bin/mongo -port 28013

MongoDB shell version: 1.8.1

connecting to: 127.0.0.1:28013/test

rs1:SECONDARY> rs.slaveOk()

rs1:SECONDARY> db.c1.find()

{ "_id" : ObjectId("4fc760d2383ede1dce14ef86"), "age" : 10 }

rs1:SECONDARY>

21.4.3.1.2 通过数据库快照(--fastsync)和oplog增加节点

通过oplog直接进行增加节点操作简单且无需人工干预过多,但oplog是capped collection,采用循环的方式进行日志处理,所以采用oplog的方式进行增加节点,有可能导致数据的不一致,因为日志中存储的信息有可能已经刷新过了。不过没关系,我们可以通过数据库快照(--fastsync)和oplog结合的方式来增加节点,这种方式的操作流程是,先取某一个复制集成员的物理文件来做为初始化数据,然后剩余的部分用oplog日志来追,最终达到数据一致性

 

①、取某一个复制集成员的物理文件来做为初始化数据

[root@localhost ~]# scp -r /data/data/r3 /data/data/r4

[root@localhost ~]# echo "this is rs1 super secret key" > /data/key/r4

[root@localhost ~]# chmod 600 /data/key/r4

 

②、在取完物理文件后,在c1集中插入一条新文档,用于最后验证此更新也同步了

rs1:PRIMARY> db.c1.find()

{ "_id" : ObjectId("4fc760d2383ede1dce14ef86"), "age" : 10 }

rs1:PRIMARY> db.c1.insert({age:20})

rs1:PRIMARY> db.c1.find()         

{ "_id" : ObjectId("4fc760d2383ede1dce14ef86"), "age" : 10 }

{ "_id" : ObjectId("4fc7748f479e007bde6644ef"), "age" : 20 }

rs1:PRIMARY>

 

③、启用28014这个端口给新的节点

/Apps/mongo/bin/mongod --replSet rs1 --keyFile /data/key/r4 --fork --port 28014 --dbpath /data/data/r4 --logpath=/data/log/r4.log --logappend--fastsync

 

 

④、添加28014节点

rs1:PRIMARY> rs.add("localhost:28014")

{ "ok" : 1 }

 

⑤、验证数据已经同步过来了

[root@localhost data]# /Apps/mongo/bin/mongo -port 28014

MongoDB shell version: 1.8.1

connecting to: 127.0.0.1:28014/test

rs1:SECONDARY> rs.slaveOk()

rs1:SECONDARY> db.c1.find()

{ "_id" : ObjectId("4fc760d2383ede1dce14ef86"), "age" : 10 }

{ "_id" : ObjectId("4fc7748f479e007bde6644ef"), "age" : 20 }

rs1:SECONDARY>

21.4.3.2 减少节点

下面将刚刚添加的两个新节点28013和28014从复制集中去除掉,只需执行rs.remove指令就可以了,具体如下:

rs1:PRIMARY> rs.remove("localhost:28014")

{ "ok" : 1 }

rs1:PRIMARY> rs.remove("localhost:28013")

{ "ok" : 1 }

 

查看复制集状态,可以看到现在只有28010、28011、28012这三个成员,原来的28013和28014都成功去除了

rs1:PRIMARY> rs.status()

{

        "set" : "rs1",

        "date" : ISODate("2012-05-31T14:08:29Z"),

        "myState" : 1,

        "members" : [

                {

                        "_id" : 0,

                        "name" : "localhost:28010",

                        "health" : 1,

                        "state" : 1,

                        "stateStr" : "PRIMARY",

                        "optime" : {

                                "t" : 1338473273000,

                                "i" : 1

                        },

                        "optimeDate" : ISODate("2012-05-31T14:07:53Z"),

                        "self" : true

                },

                {

                        "_id" : 1,

                        "name" : "localhost:28011",

                        "health" : 1,

                        "state" : 2,

                        "stateStr" : "SECONDARY",

                        "uptime" : 34,

                        "optime" : {

                                "t" : 1338473273000,

                                "i" : 1

                        },

                        "optimeDate" : ISODate("2012-05-31T14:07:53Z"),

                        "lastHeartbeat" : ISODate("2012-05-31T14:08:29Z")

                },

                {

                        "_id" : 2,

                        "name" : "localhost:28012",

                        "health" : 1,

                        "state" : 2,

                        "stateStr" : "SECONDARY",

                        "uptime" : 34,

                        "optime" : {

                                "t" : 1338473273000,

                                "i" : 1

                        },

                        "optimeDate" : ISODate("2012-05-31T14:07:53Z"),

                        "lastHeartbeat" : ISODate("2012-05-31T14:08:29Z")

                }

        ],

        "ok" : 1

}

rs1:PRIMARY>

 -------------------------------------------------------------------

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