1.配置允许在从节点读取数据

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默认MongoDB 复制集的从节点不能读取数据，可以使用 rs.slaveOk()  命令允许能够在从节点读取数据。

abc:PRIMARY> show dbs                        #在主节点上可以读取数据
admin   0.000GB
config  0.000GB
local   0.000GB
school  0.000GB
abc:PRIMARY> exit
bye
[root@localhost logs]# mongo --port 27018                        #进入端口为27018 的从节点
MongoDB shell version v3.6.7
connecting to: mongodb://127.0.0.1:27018/
abc:SECONDARY> show dbs                                             #查看数据库
2018-09-13T14:55:03.037+0800 E QUERY    [thread1] Error: listDatabases failed:{        #无法读取数据
     "operationTime" : Timestamp(1536821694, 1),
     "ok" : 0,
     "errmsg" : "not master and slaveOk=false",

    abc:SECONDARY> rs.slaveOk()                   #使用命令 rs.slaveOk() 命令允许能够在从节点读取数据
abc:SECONDARY> show dbs
admin   0.000GB
config  0.000GB
local   0.000GB
school  0.000GB
abc:SECONDARY>

2.查看复制状态信息

abc:SECONDARY> rs.help()

rs.printReplicationInfo()                  check oplog size and time range                               
rs.printSlaveReplicationInfo()             check replica set members and replication lag  

abc:SECONDARY> rs.printReplicationInfo()                                    #查看日志大小和时间范围
configured oplog size:   990MB
log length start to end: 3482secs (0.97hrs)
oplog first event time:  Thu Sep 13 2018 14:12:02 GMT+0800 (CST)
oplog last event time:   Thu Sep 13 2018 15:10:04 GMT+0800 (CST)
now:                     Thu Sep 13 2018 15:10:06 GMT+0800 (CST)
abc:SECONDARY> rs.printSlaveReplicationInfo()               #查看那些从节点复制数据                      
source: 192.168.213.184:27018
     syncedTo: Thu Sep 13 2018 15:11:54 GMT+0800 (CST)
     0 secs (0 hrs) behind the primary
source: 192.168.213.184:27019
     syncedTo: Thu Sep 13 2018 15:11:54 GMT+0800 (CST)
     0 secs (0 hrs) behind the primary

由此可看出仲裁节点并不具备数据复制

3. .更改oplog 大小

         oplog 即 opreations 的缩写，存储在 local 数据库中。oplog 中新操作会自动替换旧的操作，以保证 oplog 不会超过预设的大小。默认情况下。oplog 大小会占用64位的实例5% 的磁盘空间。尽量保证主节点的oplog 足够大，能够存放相当长时间的操作记录。

（1）首先关闭从节点服务器，从复制集中退出，暂时成为单实例

abc:SECONDARY> use admin
switched to db admin

abc:SECONDARY> db.shutdownServer()                     #关闭服务
server should be down...

[root@localhost logs]# vim /etc/mongod2.conf              #更改实例2 的配置文件

port: 27028                                               #端口号更改

#replication:
#  replSetName: abc                             #注销复制集

（2）以端口号为 27028 进入数据库

[root@localhost logs]# mongod -f /etc/mongod2.conf
about to fork child process, waiting until server is ready for connections.
forked process: 40575
child process started successfully, parent exiting
[root@localhost logs]# mongo --port 27028
MongoDB shell version v3.6.7
connecting to: mongodb://127.0.0.1:27028/

（3）对oplog 进行完全备份

[root@localhost logs]# mongodump --port 27028 --db local --collection 'oplog.rs'
2018-09-13T15:30:19.876+0800    writing local.oplog.rs to
2018-09-13T15:30:19.881+0800    done dumping local.oplog.rs (376 documents)

（4）删除原有的日志文件

> use local
switched to db local
> show tables
me
oplog.rs
replset.election
replset.minvalid
replset.oplogTruncateAfterPoint
startup_log
system.replset
system.rollback.id
> db.oplog.rs.drop()
true
>  db.runCommand({create:"oplog.rs",capped:true,size:(2 * 1024 * 1024 * 1024)})        #原型创建 oplog.rs   指定大小
{ "ok" : 1 }
> use admin
switched to db admin
> db.shutdownServer()                      #关闭服务
server should be down...

（5）把独立的实例 mongodb2 恢复到复制集，登录。

> exit
bye
[root@localhost logs]# vim /etc/mongod2.conf          #把独立的实例 mongodb2 恢复到复制集

port: 27018                      #把端口号改回为27018

replication:                               #启用复制集
   replSetName: abc
   oplogSizeMB: 2048              #指定 oplog 大小

[root@localhost logs]# mongod -f /etc/mongod2.conf
about to fork child process, waiting until server is ready for connections.
forked process: 40835
child process started successfully, parent exiting
[root@localhost logs]# mongo --port 27018
MongoDB shell version v3.6.7
connecting to: mongodb://127.0.0.1:27018/

abc:SECONDARY> rs.printReplicationInfo()    

configured oplog size:   2048MB
log length start to end: 90secs (0.03hrs)
oplog first event time:  Thu Sep 13 2018 15:44:15 GMT+0800 (CST)
oplog last event time:   Thu Sep 13 2018 15:45:45 GMT+0800 (CST)
now:                     Thu Sep 13 2018 15:45:54 GMT+0800 (CST)

4 .部署认证复制

（1）

abc:PRIMARY> use admin                    
switched to db admin

abc:PRIMARY> db.createUser({"user":"root","pwd":"123","roles":["root"]})    #创建用户root  设置密码为 123
Successfully added user: { "user" : "root", "roles" : [ "root" ] }

（2）在每个实例的配置文件中开启认证功能

abc:PRIMARY> exit
bye
[root@localhost logs]# vim /etc/mongod.conf

security:
    keyFile: /usr/bin/abckey1                         #验证文件路径
    clusterAuthMode: keyFile                          #验证模式，文件验证

[root@localhost logs]# vim /etc/mongod2.conf

security:
    keyFile: /usr/bin/abckey2
    clusterAuthMode:keyFile

[root@localhost logs]# vim /etc/mongod3.conf

security:
    keyFile: /usr/bin/abckey3
    clusterAuthMode:keyFile

[root@localhost logs]# vim /etc/mongod4.conf

security:
    keyFile: /usr/bin/abckey4
    clusterAuthMode:keyFile

[root@localhost logs]# cd /usr/bin/
[root@localhost bin]# echo "abc key" > abckey1                 #生成4个密钥文件
[root@localhost bin]# echo "abc key" > abckey2
[root@localhost bin]# echo "abc key" > abckey3
[root@localhost bin]# echo "abc key" > abckey4

（3）重启4个实例

[root@localhost bin]# chmod 600 abc*              # 把文件 abc 权限设置为600             
[root@localhost bin]# mongod -f /etc/mongod.conf                #启动服务
about to fork child process, waiting until server is ready for connections.
forked process: 41828
child process started successfully, parent exiting
[root@localhost bin]# mongod -f /etc/mongod2.conf --shutdown
killing process with pid: 40835
[root@localhost bin]# mongod -f /etc/mongod2.conf
about to fork child process, waiting until server is ready for connections.
forked process: 42252
child process started successfully, parent exiting
[root@localhost bin]# mongod -f /etc/mongod3.conf --shutdown
killing process with pid: 4881
[root@localhost bin]# mongod -f /etc/mongod3.conf
about to fork child process, waiting until server is ready for connections.
forked process: 42451
child process started successfully, parent exiting
[root@localhost bin]# mongod -f /etc/mongod4.conf --shutdown
killing process with pid: 4909
[root@localhost bin]# mongod -f /etc/mongod4.conf
about to fork child process, waiting until server is ready for connections.
forked process: 42634
child process started successfully, parent exiting

（4）登录主节点服务器验证  

[root@localhost bin]# mongo --port 27018
MongoDB shell version v3.6.7
connecting to: mongodb://127.0.0.1:27018/
MongoDB server version: 3.6.7
abc:PRIMARY> show dbs                                          #在主节点查看数据库
2018-09-13T16:49:14.542+0800 E QUERY    [thread1] Error: listDatabases failed:{           #无法查询
     "operationTime" : Timestamp(1536828545, 1),
     "ok" : 0,

abc:PRIMARY> rs.status()                #查看各节点状态，也无法查询
{
     "operationTime" : Timestamp(1536828575, 1),
     "ok" : 0,
     "errmsg" : "not authorized on admin to execute command { replSetGetStatus: 1.0, $clusterTime: { clusterTime: Timestamp(1536828545, 1), signature: { hash: BinData(0, 40060B8D2AC8AC1AE68D47E9332835D2040120C2), keyId: 6600587920397041666 } }, $db: \"admin\" }",
     "code" : 13,
     "codeName" : "Unauthorized",
     "$clusterTime" : {
         "clusterTime" : Timestamp(1536828575, 1),
         "signature" : {
             "hash" : BinData(0,"gSi7raqiqfKJKSF42wlgu2rvggE="),
             "keyId" : NumberLong("6600587920397041666")
         }
     }
}

abc:PRIMARY> use admin               #进入admin 数据库
switched to db admin
abc:PRIMARY> db.auth("root","123")           #进行身份验证
1
abc:PRIMARY> show dbs                 #再查看数据库
admin   0.000GB
config  0.000GB
local   0.000GB
school  0.000GB

（5）进入从节点服务器进行验证

[root@localhost bin]# mongo --port 27019
MongoDB shell version v3.6.7
connecting to: mongodb://127.0.0.1:27019/
MongoDB server version: 3.6.7
abc:SECONDARY> show dbs                    #查看数据库
2018-09-13T16:55:14.429+0800 E QUERY    [thread1] Error: listDatabases failed:{
     "operationTime" : Timestamp(1536828905, 1),
     "ok" : 0,

abc:SECONDARY> rs.slaveOk()

abc:SECONDARY> use admin                #进行身份验证
switched to db admin
abc:SECONDARY> db.auth("root","123")
1

abc:SECONDARY> show dbs
admin   0.000GB
config  0.000GB
local   0.000GB
school  0.000GB

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