## mongodb复制(副本集)
mongodb副本集的好处：
1. 保证数据的安全性
2. 数据高可用
3. 灾难恢复
4. 无需停机维护
5. 分布式读取数据
###副本集的配置
需要准备至少三个节点来测试，本次为了方便使用同一台机器上的不同端口号启动三个节点：
~~~
192.168.226.130:27017 node1
192.168.226.130:27018 node2
192.168.226.130:27019 node3
~~~
在/data/文件夹下创建三个数据库node1,node2,node3
```shell script
[root@moggledb data]# mkdir node1
[root@moggledb data]# mkdir node2
[root@moggledb data]# mkdir node3
[root@moggledb data]# mkdir log
[root@moggledb data]# ll
total 16
drwxr-xr-x. 2 root root 4096 May 5 20:12 log
drwxr-xr-x. 2 root root 4096 May 5 20:12 node1
drwxr-xr-x. 2 root root 4096 May 5 20:12 node2
drwxr-xr-x. 2 root root 4096 May 5 20:12 node3
```
使用配置文件启动方式，在node1下创建配置文件并复制到另外两个节点
```shell script
[root@moggledb data]# cd node1
[root@moggledb node1]# vi mongodb-node1.conf
dbpath=/data/node1
logpath=/data/log/mongodb-node1.log
logappend=true
fork=true
bind_ip=192.168.226.130
port=27017
replSet=rs0
```
保存退出,复制到另外连个节点中，并修改dbpath,logpath及port
```shell script
[root@moggledb node1]# cp mongodb-node1.conf ../node2/mongodb-node2.conf
[root@moggledb node1]# cp mongodb-node1.conf ../node3/mongodb-node3.conf
[root@moggledb node1]# vi ../node2/mongodb-node2.conf
dbpath=/data/node2
logpath=/data/log/mongodb-node2.log
logappend=true
fork=true
bind_ip=192.168.226.130
port=27018
replSet=rs0
[root@moggledb node2]# vi ../node3/mongodb-node3.conf
dbpath=/data/node3
logpath=/data/log/mongodb-node3.log
logappend=true
fork=true
bind_ip=192.168.226.130
port=27019
replSet=rs0
```
replSet为副本集名称，同一个副本集内的节点，值要一样。
配置完毕，启动三个节点：
```shell script
[root@moggledb node2]# cd /usr/local/mongodb/bin/
[root@moggledb bin]# ./mongod -f /data/node1/mongodb-node1.conf
about to fork child process, waiting until server is ready for connections.
forked process: 2633
child process started successfully, parent exiting
[root@moggledb bin]# ./mongod -f /data/node2/mongodb-node2.conf
about to fork child process, waiting until server is ready for connections.
forked process: 2649
child process started successfully, parent exiting
[root@moggledb bin]# ./mongod -f /data/node3/mongodb-node3.conf
about to fork child process, waiting until server is ready for connections.
forked process: 2665
child process started successfully, parent exiting
[root@moggledb bin]# ps -ef |grep mongod
root 2633 1 1 20:23 ? 00:00:00 ./mongod -f /data/node1/mongodb-node1.conf
root 2649 1 2 20:24 ? 00:00:00 ./mongod -f /data/node2/mongodb-node2.conf
root 2665 1 3 20:24 ? 00:00:00 ./mongod -f /data/node3/mongodb-node3.conf
root 2680 2581 0 20:24 pts/0 00:00:00 grep mongod
[root@moggledb bin]#
```
三台节点启动成功。下面配置三个节点为副本集：
```shell script
[root@moggledb bin]# ./mongo --host 192.168.226.130 --port 27017
...
2020-05-05T20:23:43.992-0700 I CONTROL [initandlisten]
> conf = {"_id":"rs0","members":[{"_id":0,"host":"192.168.226.130:27017"},{"_id":1,"host":"192.168.226.130:27018"},{"_id":2,"host":"192.168.226.130:27019"}]}
{
"_id" : "rs0",
"members" : [
{
"_id" : 0,
"host" : "192.168.226.130:27017"
},
{
"_id" : 1,
"host" : "192.168.226.130:27018"
},
{
"_id" : 2,
"host" : "192.168.226.130:27019"
}
]
}
> rs.initiate(conf)
{ "ok" : 1 }
rs0:OTHER> rs.isMaster()
{
"setName" : "rs0",
"setVersion" : 1,
"ismaster" : true,
"secondary" : false,
"hosts" : [
"192.168.226.130:27017",
"192.168.226.130:27018",
"192.168.226.130:27019"
],
"primary" : "192.168.226.130:27017",
"me" : "192.168.226.130:27017",
"electionId" : ObjectId("5eb22f9c0520bca5e5033db3"),
"maxBsonObjectSize" : 16777216,
"maxMessageSizeBytes" : 48000000,
"maxWriteBatchSize" : 1000,
"localTime" : ISODate("2020-05-06T03:32:16.019Z"),
"maxWireVersion" : 3,
"minWireVersion" : 0,
"ok" : 1
}
rs0:PRIMARY> rs.status()
{
"set" : "rs0",
"date" : ISODate("2020-05-06T03:33:29.129Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "192.168.226.130:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 586,
"optime" : Timestamp(1588735898, 1),
"optimeDate" : ISODate("2020-05-06T03:31:38Z"),
"electionTime" : Timestamp(1588735900, 1),
"electionDate" : ISODate("2020-05-06T03:31:40Z"),
"configVersion" : 1,
"self" : true
},
{
"_id" : 1,
"name" : "192.168.226.130:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 110,
"optime" : Timestamp(1588735898, 1),
"optimeDate" : ISODate("2020-05-06T03:31:38Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:33:29.013Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:33:29.078Z"),
"pingMs" : 0,
"configVersion" : 1
},
{
"_id" : 2,
"name" : "192.168.226.130:27019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 110,
"optime" : Timestamp(1588735898, 1),
"optimeDate" : ISODate("2020-05-06T03:31:38Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:33:29.013Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:33:29.078Z"),
"pingMs" : 0,
"configVersion" : 1
}
],
"ok" : 1
}
```
当前节点为主节点PRIMARY,上面可以看出节点的详细信息。
副本集的主节点负责与客户端交互，进行读和写。从节点复制主机点数据，监听主节点 的心跳。
####副本集主从复制测试。
在主节点插入数据
```shell script
rs0:PRIMARY> show dbs
local 1.078GB
rs0:PRIMARY> use test
switched to db test
rs0:PRIMARY> db.coll.insert({"name":"zhangsan"})
WriteResult({ "nInserted" : 1 })
rs0:PRIMARY> db.coll.insert({"name":"lisi"})
WriteResult({ "nInserted" : 1 })
rs0:PRIMARY> db.coll.find()
{ "_id" : ObjectId("5eb230a80a6d7da784ff2c83"), "name" : "zhangsan" }
{ "_id" : ObjectId("5eb230ad0a6d7da784ff2c84"), "name" : "lisi" }
```
连接从节点：
```shell script
[root@moggledb bin]# ./mongo --host 192.168.226.130 --port 27018
...
2020-05-05T20:24:21.584-0700 I CONTROL [initandlisten]
rs0:SECONDARY> rs.slaveOk()
rs0:SECONDARY> show dbs
local 1.078GB
test 0.078GB
rs0:SECONDARY> use test
switched to db test
rs0:SECONDARY> db.coll.find()
{ "_id" : ObjectId("5eb230a80a6d7da784ff2c83"), "name" : "zhangsan" }
{ "_id" : ObjectId("5eb230ad0a6d7da784ff2c84"), "name" : "lisi" }
rs0:SECONDARY> rs.status()
{
"set" : "rs0",
"date" : ISODate("2020-05-06T03:45:56.163Z"),
"myState" : 2,
"syncingTo" : "192.168.226.130:27017",
"members" : [
{
"_id" : 0,
"name" : "192.168.226.130:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 857,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:45:54.692Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:45:54.665Z"),
"pingMs" : 0,
"electionTime" : Timestamp(1588735900, 1),
"electionDate" : ISODate("2020-05-06T03:31:40Z"),
"configVersion" : 1
},
{
"_id" : 1,
"name" : "192.168.226.130:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1295,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"syncingTo" : "192.168.226.130:27017",
"configVersion" : 1,
"self" : true
},
{
"_id" : 2,
"name" : "192.168.226.130:27019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 857,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:45:54.677Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:45:54.677Z"),
"pingMs" : 0,
"syncingTo" : "192.168.226.130:27017",
"configVersion" : 1
}
],
"ok" : 1
}
rs0:SECONDARY>
```
可以看出主节点插入数据，在从节点中也有数据,从节点只能读数据，不能写数据，主节点可以读写数据。
####故障转移
模拟主节点宕机，关闭主节点服务：
```shell script
[root@moggledb bin]# ./mongod --shutdown --dbpath=/data/node1
killing process with pid: 2633
[root@moggledb bin]#
```
再次查看从节点状态：
```shell script
[root@moggledb bin]# mongo --host 192.168.226.130 --port 27018
...
2020-05-05T20:24:21.584-0700 I CONTROL [initandlisten]
rs0:PRIMARY> rs.status()
{
"set" : "rs0",
"date" : ISODate("2020-05-06T03:52:08.238Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "192.168.226.130:27017",
"health" : 0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"optime" : Timestamp(0, 0),
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:52:07.354Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:50:23.111Z"),
"pingMs" : 0,
"lastHeartbeatMessage" : "Failed attempt to connect to 192.168.226.130:27017; couldn't connect to server 192.168.226.130:27017 (192.168.226.130), connection attem
pt failed",
"configVersion" : -1
},
{
"_id" : 1,
"name" : "192.168.226.130:27018",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1667,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"electionTime" : Timestamp(1588737026, 1),
"electionDate" : ISODate("2020-05-06T03:50:26Z"),
"configVersion" : 1,
"self" : true
},
{
"_id" : 2,
"name" : "192.168.226.130:27019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1229,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:52:07.216Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:52:07.197Z"),
"pingMs" : 0,
"configVersion" : 1
}
],
"ok" : 1
}
```
从上面状态信息可以看出，27017节点无心跳，27018节点变为主节点：`{"stateStr":"PRIMARY"}`
如果此时重启27017节点：
```shell script
[root@moggledb bin]# ./mongod -f /data/node1/mongodb-node1.conf
rs0:SECONDARY> rs.status()
{
"set" : "rs0",
"date" : ISODate("2020-05-06T03:54:46.892Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "192.168.226.130:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 17,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:54:45.678Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:54:45.725Z"),
"pingMs" : 0,
"configVersion" : 1
},
{
"_id" : 1,
"name" : "192.168.226.130:27018",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1825,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"electionTime" : Timestamp(1588737026, 1),
"electionDate" : ISODate("2020-05-06T03:50:26Z"),
"configVersion" : 1,
"self" : true
},
{
"_id" : 2,
"name" : "192.168.226.130:27019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1387,
"optime" : Timestamp(1588736173, 1),
"optimeDate" : ISODate("2020-05-06T03:36:13Z"),
"lastHeartbeat" : ISODate("2020-05-06T03:54:45.517Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T03:54:45.517Z"),
"pingMs" : 0,
"configVersion" : 1
}
],
"ok" : 1
}
```
27017节点仍为从节点，27018为主节点。可以为节点配置优先级，这样主节点重启后仍是主节点。
**只有主节点才可以设置副本集配置**
所以先进入主节点的shell命令行：
```shell script
rs0:PRIMARY> rs.conf()
{
"_id" : "rs0",
"version" : 1,
"members" : [
{
"_id" : 0,
"host" : "192.168.226.130:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : 0,
"votes" : 1
},
{
"_id" : 1,
"host" : "192.168.226.130:27018",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : 0,
"votes" : 1
},
{
"_id" : 2,
"host" : "192.168.226.130:27019",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : 0,
"votes" : 1
}
],
"settings" : {
"chainingAllowed" : true,
"heartbeatTimeoutSecs" : 10,
"getLastErrorModes" : {
},
"getLastErrorDefaults" : {
"w" : 1,
"wtimeout" : 0
}
}
}
```
将27017优先级设为三个节点的最高值：
```shell script
rs0:PRIMARY> var conf=rs.conf()
rs0:PRIMARY> conf.members[0].priority=5
5
rs0:PRIMARY> rs.reconfig(conf)
```
然后重新启动27017节点
```shell script
[root@moggledb bin]# ./mongod --shutdown --dbpath=/data/node1
killing process with pid: 4252
[root@moggledb bin]# ./mongod -f /data/node1/mongodb-node1.conf
about to fork child process, waiting until server is ready for connections.
forked process: 5614
child process started successfully, parent exiting
[root@moggledb bin]# ./mongo --host 192.168.226.130 --port 27017
...
rs0:SECONDARY> rs.isMaster()
rs0:SECONDARY> rs.isMaster()
{
"setName" : "rs0",
"setVersion" : 2,
"ismaster" : true,
"secondary" : false,
"hosts" : [
"192.168.226.130:27017",
"192.168.226.130:27018",
"192.168.226.130:27019"
],
"primary" : "192.168.226.130:27017",
"me" : "192.168.226.130:27017",
"electionId" : ObjectId("5eb23de4b1aea8240124474b"),
"maxBsonObjectSize" : 16777216,
"maxMessageSizeBytes" : 48000000,
"maxWriteBatchSize" : 1000,
"localTime" : ISODate("2020-05-06T04:32:49.878Z"),
"maxWireVersion" : 3,
"minWireVersion" : 0,
"ok" : 1
}
rs0:PRIMARY> rs.status()
{
"set" : "rs0",
"date" : ISODate("2020-05-06T04:33:55.150Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "192.168.226.130:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 106,
"optime" : Timestamp(1588739463, 1),
"optimeDate" : ISODate("2020-05-06T04:31:03Z"),
"electionTime" : Timestamp(1588739556, 1),
"electionDate" : ISODate("2020-05-06T04:32:36Z"),
"configVersion" : 2,
"self" : true
},
{
"_id" : 1,
"name" : "192.168.226.130:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 105,
"optime" : Timestamp(1588739463, 1),
"optimeDate" : ISODate("2020-05-06T04:31:03Z"),
"lastHeartbeat" : ISODate("2020-05-06T04:33:53.661Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T04:33:54.069Z"),
"pingMs" : 23,
"configVersion" : 2
},
{
"_id" : 2,
"name" : "192.168.226.130:27019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 105,
"optime" : Timestamp(1588739463, 1),
"optimeDate" : ISODate("2020-05-06T04:31:03Z"),
"lastHeartbeat" : ISODate("2020-05-06T04:33:53.661Z"),
"lastHeartbeatRecv" : ISODate("2020-05-06T04:33:55.124Z"),
"pingMs" : 23,
"configVersion" : 2
}
],
"ok" : 1
}
```
可以看出27017重新成为主节点
