在CentOS7上部署MongoDB复制集和复制集的管理维护

MongoDB复制集的概述

复制集是额外的数据副本，是跨多个服务器同步数据的过程，复制集提供了冗余并增加了数据可用性，通过复制集可以对硬件故障和中断的服务进行恢复。

成都创新互联服务项目包括蒲江县网站建设、蒲江县网站制作、蒲江县网页制作以及蒲江县网络营销策划等。多年来，我们专注于互联网行业，利用自身积累的技术优势、行业经验、深度合作伙伴关系等，向广大中小型企业、政府机构等提供互联网行业的解决方案，蒲江县网站推广取得了明显的社会效益与经济效益。目前，我们服务的客户以成都为中心已经辐射到蒲江县省份的部分城市，未来相信会继续扩大服务区域并继续获得客户的支持与信任！

复制集工作原理

• MongoDB的复制集至少需要两个节点。其中一个是主节点（primary），负责处理客户端的请求，其余都是从节点（Secondary）,负责复制主节点上的数据。
• MongoDB各个节点常见的搭配方式为：一主一从或一主多从。主节点记录其上的所有操作到oplog中，从节点定期轮询主节点获取这些操作，然后对自己的数副本执行这些操作，从而保证从节点的数据与主节点一致。

复制集的特点

• N个节点的群集
• 任何节点可作为主节点
• 所有写入操作都在主节点上
• 自动故障转移
• 自动恢复

MongoDB复制集部署

1.配置复制集

（1）创建数据文件和日志文件存储路径

[root@localhost ~]# mkdir -p /data/mongodb/mongodb{2,3,4}
[root@localhost ~]# cd /data/mongodb/
[root@localhost mongodb]# mkdir logs
[root@localhost mongodb]# touch logs/mongodb{2,3,4}.log
[root@localhost mongodb]# cd logs/
[root@localhost logs]# ls
mongodb2.log  mongodb3.log  mongodb4.log
[root@localhost logs]# chmod 777 *.log

（2）编辑4个MongoDB实例的配置文件

先编辑Mongodb的配置文件，配置replSet参数值都为kgcrs,并复制3份，具体操作如下：

[root@localhost etc]# vim mongod.conf 
  path: /var/log/mongodb/mongod.log

# Where and how to store data.
storage:
  dbPath: /var/lib/mongo
  journal:
    enabled: true
#  engine:
#  mmapv1:
#  wiredTiger:

# how the process runs
processManagement:
  fork: true  # fork and run in background
  pidFilePath: /var/run/mongodb/mongod.pid  # location of pidfile
  timeZoneInfo: /usr/share/zoneinfo

# network interfaces
net:
  port: 27017
  bindIp: 0.0.0.0  # Listen to local interface only, comment to listen on all interfaces.

#security:

#operationProfiling:

replication:
     replSetName: kgcrs    

#sharding:

## Enterprise-Only Options

#auditLog:

#snmp:

然后将mongodb2.conf中的port参数配置为27018,mongodb3.conf中的port参数配置为27019，mongodb4.conf中的port参数配置为27020。同样也将dbpath和logpath参数修改为对应的路径值。

（3）启动4个MongoDB节点实列并查看进程信息

[root@localhost etc]# mongod -f /etc/mongod.conf --shutdown  //先关闭//
[root@localhost etc]# mongod -f /etc/mongod.conf //再开启//
[root@localhost etc]# mongod -f /etc/mongod2.conf
[root@localhost etc]# mongod -f /etc/mongod3.conf 
[root@localhost etc]# mongod -f /etc/mongod4.conf 
[root@localhost etc]# netstat -ntap | grep mongod
tcp        0      0 0.0.0.0:27019           0.0.0.0:*               LISTEN      17868/mongod        
tcp        0      0 0.0.0.0:27020           0.0.0.0:*               LISTEN      17896/mongod        
tcp        0      0 0.0.0.0:27017           0.0.0.0:*               LISTEN      17116/mongod        
tcp        0      0 0.0.0.0:27018           0.0.0.0:*               LISTEN      17413/mongod

（4）配置三个节点的复制集

[root@localhost etc]# mongo
> rs.status()    //查看复制集//
{
    "info" : "run rs.initiate(...) if not yet done for the set",
    "ok" : 0,
    "errmsg" : "no replset config has been received",
    "code" : 94,
    "codeName" : "NotYetInitialized",
    "$clusterTime" : {
        "clusterTime" : Timestamp(0, 0),
        "signature" : {
            "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
            "keyId" : NumberLong(0)
        }
    }
}
> cfg={"_id":"kgcrs","members":[{"_id":0,"host":"192.168.126.132:27017"},{"_id":1,"host":"192.168.126.132:27018"},{"_id":2,"host":"192.168.126.132:27019"}]}  //添加复制集//
{
    "_id" : "kgcrs",
    "members" : [
        {
            "_id" : 0,
            "host" : "192.168.126.132:27017"
        },
        {
            "_id" : 1,
            "host" : "192.168.126.132:27018"
        },
        {
            "_id" : 2,
            "host" : "192.168.126.132:27019"
        }
    ]
}
> rs.initiate(cfg)   //初始化配置时保证从节点没有数据//

（5）查看复制集状态

启动复制集后，再次通过rs.status()命令查看复制集的完整状态信息

kgcrs:SECONDARY> rs.status()
{
    "set" : "kgcrs",
    "date" : ISODate("2018-07-17T07:18:52.047Z"),
    "myState" : 1,
    "term" : NumberLong(1),
    "syncingTo" : "",
    "syncSourceHost" : "",
    "syncSourceId" : -1,
    "heartbeatIntervalMillis" : NumberLong(2000),
    "optimes" : {
        "lastCommittedOpTime" : {
            "ts" : Timestamp(1531811928, 1),
            "t" : NumberLong(1)
        },
        "readConcernMajorityOpTime" : {
            "ts" : Timestamp(1531811928, 1),
            "t" : NumberLong(1)
        },
        "appliedOpTime" : {
            "ts" : Timestamp(1531811928, 1),
            "t" : NumberLong(1)
        },
        "durableOpTime" : {
            "ts" : Timestamp(1531811928, 1),
            "t" : NumberLong(1)
        }
    },
    "members" : [
        {
            "_id" : 0,
            "name" : "192.168.126.132:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",       //主节点//
            "uptime" : 2855,
            "optime" : {
                "ts" : Timestamp(1531811928, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2018-07-17T07:18:48Z"),
            "syncingTo" : "",
            "syncSourceHost" : "",
            "syncSourceId" : -1,
            "infoMessage" : "could not find member to sync from",
            "electionTime" : Timestamp(1531811847, 1),
            "electionDate" : ISODate("2018-07-17T07:17:27Z"),
            "configVersion" : 1,
            "self" : true,
            "lastHeartbeatMessage" : ""
        },
        {
            "_id" : 1,
            "name" : "192.168.126.132:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",     //从节点//
            "uptime" : 95,
            "optime" : {
                "ts" : Timestamp(1531811928, 1),
                "t" : NumberLong(1)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531811928, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2018-07-17T07:18:48Z"),
            "optimeDurableDate" : ISODate("2018-07-17T07:18:48Z"),
            "lastHeartbeat" : ISODate("2018-07-17T07:18:51.208Z"),
            "lastHeartbeatRecv" : ISODate("2018-07-17T07:18:51.720Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "192.168.126.132:27017",
            "syncSourceHost" : "192.168.126.132:27017",
            "syncSourceId" : 0,
            "infoMessage" : "",
            "configVersion" : 1
        },
        {
            "_id" : 2,
            "name" : "192.168.126.132:27019",
            "health" : 1,         
            "state" : 2,             
            "stateStr" : "SECONDARY",      //从节点//
            "uptime" : 95,
            "optime" : {
                "ts" : Timestamp(1531811928, 1),
                "t" : NumberLong(1)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531811928, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2018-07-17T07:18:48Z"),
            "optimeDurableDate" : ISODate("2018-07-17T07:18:48Z"),
            "lastHeartbeat" : ISODate("2018-07-17T07:18:51.208Z"),
            "lastHeartbeatRecv" : ISODate("2018-07-17T07:18:51.822Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "192.168.126.132:27017",
            "syncSourceHost" : "192.168.126.132:27017",
            "syncSourceId" : 0,
            "infoMessage" : "",
            "configVersion" : 1
        }
    ],
    "ok" : 1,
    "operationTime" : Timestamp(1531811928, 1),
    "$clusterTime" : {
        "clusterTime" : Timestamp(1531811928, 1),
        "signature" : {
            "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
            "keyId" : NumberLong(0)
        }
    }
}

其中，health为1代表健康，0代表宕机。state为1代表主节点，为2代表从节点。

在复制集初始化配置时要保证从节点上没有数据

MongoDB复制集切换

MongoDB复制集可以实现群集的高可用，当其中主节点出现故障时会自动切换到其他节点。也可手动进行复制集的主从切换。

1.故障转移切换

[root@localhost etc]# ps aux | grep mongod   //查看进程//
root      17116  1.2  5.8 1546916 58140 ?       Sl   14:31   0:51 mongod -f /etc/mongod.conf
root      17413  1.0  5.7 1445624 57444 ?       Sl   14:34   0:39 mongod -f /etc/mongod2.conf
root      17868  1.2  5.5 1446752 55032 ?       Sl   15:05   0:23 mongod -f /etc/mongod3.conf
root      17896  0.8  4.7 1037208 47552 ?       Sl   15:05   0:16 mongod -f /etc/mongod4.conf
root      18836  0.0  0.0 112676   980 pts/1    S+   15:38   0:00 grep --color=auto mongod
[root@localhost etc]# kill -9 17116   ///杀死27017进程//
[root@localhost etc]# ps aux | grep mongod
root      17413  1.0  5.7 1453820 57456 ?       Sl   14:34   0:40 mongod -f /etc/mongod2.conf
root      17868  1.2  5.5 1454948 55056 ?       Sl   15:05   0:24 mongod -f /etc/mongod3.conf
root      17896  0.8  4.7 1037208 47552 ?       Sl   15:05   0:16 mongod -f /etc/mongod4.conf
root      18843  0.0  0.0 112676   976 pts/1    R+   15:38   0:00 grep --color=auto mongod
[root@localhost etc]# mongo --port 27019
kgcrs:PRIMARY> rs.status()

    "members" : [
        {
            "_id" : 0,
            "name" : "192.168.126.132:27017",
            "health" : 0,       //宕机状态//
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "optime" : {
                "ts" : Timestamp(0, 0),
                "t" : NumberLong(-1)

        {
            "_id" : 1,
            "name" : "192.168.126.132:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",     //从节点//
            "uptime" : 1467,
            "optime" : {
                "ts" : Timestamp(1531813296, 1),
                "t" : NumberLong(2)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531813296, 1),
                "t" : NumberLong(2)
            },

        {
            "_id" : 2,
            "name" : "192.168.126.132:27019",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",     //主节点//
            "uptime" : 2178,
            "optime" : {
                "ts" : Timestamp(1531813296, 1),
                "t" : NumberLong(2)

}

2.手动进行主从切换

kgcrs:PRIMARY> rs.freeze(30)      //暂停30s不参与选举
kgcrs:PRIMARY> rs.stepDown(60,30)  //交出主节点位置，维持从节点状态不少于60秒，等待30秒使主节点和从节点日志同步

2018-07-17T15:46:19.079+0800 E QUERY    [thread1] Error: error doing query: failed: network error while attempting to run command 'replSetStepDown' on host '127.0.0.1:27019'  :
DB.prototype.runCommand@src/mongo/shell/db.js:168:1
DB.prototype.adminCommand@src/mongo/shell/db.js:186:16
rs.stepDown@src/mongo/shell/utils.js:1341:12
@(shell):1:1
2018-07-17T15:46:19.082+0800 I NETWORK  [thread1] trying reconnect to 127.0.0.1:27019 (127.0.0.1) failed
2018-07-17T15:46:19.085+0800 I NETWORK  [thread1] reconnect 127.0.0.1:27019 (127.0.0.1) ok
kgcrs:SECONDARY>    //交出主节点后立马变成从节点//
kgcrs:SECONDARY> rs.status()
    "_id" : 0,
            "name" : "192.168.126.132:27017",
            "health" : 0,      //宕机状态//
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "optime" : {
                "ts" : Timestamp(0, 0),
                "t" : NumberLong(-1)
            },

        {
            "_id" : 1,
            "name" : "192.168.126.132:27018",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",       //主节点状态//
            "uptime" : 1851,
            "optime" : {
                "ts" : Timestamp(1531813679, 1),
                "t" : NumberLong(3)

        {
            "_id" : 2,
            "name" : "192.168.126.132:27019",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",     //从节点状态//
            "uptime" : 2563,
            "optime" : {
                "ts" : Timestamp(1531813689, 1),
                "t" : NumberLong(3)

MongoDB复制集的选举原理

节点类型分为标准节点（host）、被动节点（passive）和仲裁节点（arbiter）。

• 只有标准节点可能被选举为活跃（primary）节点，有选举权。被动节点有完整副本，不可能成为活跃节点，有选举权。仲裁节点不复制数据，不可能成为活跃节点，只有选举权。
• 标准节点与被动节点的区别：priority值高者是标准节点，低者为被动节点。
• 选举规则是票数高者获胜，priority是优先权为0~1000的值，相当于额外增加0~1000的票数。选举结果：票数高者获胜；若票数相同，数据新者获胜。

1.配置复制集的优先级

1）重新配置4个节点的MongoDB复制集，设置两个标准节点，一个被动节点和一个仲裁节点。

[root@localhost etc]# mongo
> cfg={"_id":"kgcrs","members":[{"_id":0,"host":"192.168.126.132:27017","priority":100},{"_id":1,"host":"192.168.126.132:27018","priority":100},{"_id":2,"host":"192.168.126.132:27019","priority":0},{"_id":3,"host":"192.168.126.132:27020","arbiterOnly":true}]}
> rs.initiate(cfg)     //重新配置//
kgcrs:SECONDARY> rs.isMaster()
{
    "hosts" : [                 //标准节点//
        "192.168.126.132:27017",
        "192.168.126.132:27018"
    ],
    "passives" : [             //被动节点//
        "192.168.126.132:27019"
    ],
    "arbiters" : [            //仲裁节点//
        "192.168.126.132:27020"

2）模拟主节点故障

如果主节点出现故障，另一个标准节点将会选举成为新的主节点

[root@localhost etc]# mongod -f /etc/mongod.conf --shutdown   //标准节点27017//
[root@localhost etc]# mongo --port 27018   //此时会选举第二个标准节点为主节点//
kgcrs:PRIMARY> rs.status()
    "_id" : 0,
            "name" : "192.168.126.132:27017",
            "health" : 0,      //宕机状态//
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "optime" : {
                "ts" : Timestamp(0, 0),
                "t" : NumberLong(-1)
    "_id" : 1,
            "name" : "192.168.126.132:27018",
            "health" : 1,
            "state" : 1,        
            "stateStr" : "PRIMARY",    //标准节点//
            "uptime" : 879,
            "optime" : {
                "ts" : Timestamp(1531817473, 1),
                "t" : NumberLong(2)
    "_id" : 2,
            "name" : "192.168.126.132:27019",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",   //被动节点//
            "uptime" : 569,
            "optime" : {
                "ts" : Timestamp(1531817473, 1),
                "t" : NumberLong(2)
        "_id" : 3,
            "name" : "192.168.126.132:27020",
            "health" : 1,
            "state" : 7,
            "stateStr" : "ARBITER",   //仲裁节点//
            "uptime" : 569,     

3）模拟所有标准节点出现故障

所有标准节点都出现故障，被动节点也不能成为主节点

[root@localhost etc]# mongod -f /etc/mongod2.conf --shutdown //关闭标准节点27018//
[root@localhost etc]# mongo --port 27019
kgcrs:SECONDARY> rs.status()

            "_id" : 0,
            "name" : "192.168.126.132:27017",
            "health" : 0,     //宕机状态//
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "_id" : 1,
            "name" : "192.168.126.132:27018",
            "health" : 0,      //宕机状态//
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "_id" : 2,
            "name" : "192.168.126.132:27019",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",   //被动节点//
            "uptime" : 1403,

            "_id" : 3,
            "name" : "192.168.126.132:27020",
            "health" : 1,
            "state" : 7,
            "stateStr" : "ARBITER",    //仲裁节点//

MongoDB复制集管理

1.配置允许在从节点读取数据

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。

[root@localhost etc]# mongo --port 27017
kgcrs:SECONDARY> show dbs    //读取不到数据库信息//
2018-07-17T17:11:31.570+0800 E QUERY    [thread1] Error: listDatabases failed:{
    "operationTime" : Timestamp(1531818690, 1),
    "ok" : 0,
    "errmsg" : "not master and slaveOk=false",
    "code" : 13435,
    "codeName" : "NotMaste
    kgcrs:SECONDARY> rs.slaveOk()
kgcrs:SECONDARY> show dbs
admin   0.000GB
config  0.000GB
local   0.000GB

2.查看复制状态信息

可以使用 rs.printReplicationInfo()和rs.printSlaveReplicationInfo()命令查看复制集状态。

kgcrs:SECONDARY> rs.printReplicationInfo()
configured oplog size:   990MB
log length start to end: 2092secs (0.58hrs)
oplog first event time:  Tue Jul 17 2018 16:41:48 GMT+0800 (CST)
oplog last event time:   Tue Jul 17 2018 17:16:40 GMT+0800 (CST)
now:                     Tue Jul 17 2018 17:16:46 GMT+0800 (CST)
kgcrs:SECONDARY>  rs.printSlaveReplicationInfo()
source: 192.168.126.132:27017
    syncedTo: Tue Jul 17 2018 17:16:50 GMT+0800 (CST)
    0 secs (0 hrs) behind the primary 
source: 192.168.126.132:27019
    syncedTo: Tue Jul 17 2018 17:16:50 GMT+0800 (CST)
    0 secs (0 hrs) behind the primary

3.部署认证复制

kgcrs:PRIMARY> use admin
kgcrs:PRIMARY> db.createUser({"user":"root","pwd":"123","roles":["root"]})
[root@localhost ~]# vim /etc/mongod.conf   //分别编辑四个配置文件//
....
security:
    keyFile: /usr/bin/kgcrskey1      //验证路径//
    clusterAuthMode: keyFile        //验证类型//
    [root@localhost ~]# vim /etc/mongod2.conf 
[root@localhost ~]# vim /etc/mongod3.conf 
[root@localhost ~]# vim /etc/mongod4.conf 
[root@localhost bin]# echo "kgcrs key"> kgcrskey1   //生成4个实例的密钥文件//
[root@localhost bin]# echo "kgcrs key"> kgcrskey2
[root@localhost bin]# echo "kgcrs key"> kgcrskey3
[root@localhost bin]# echo "kgcrs key"> kgcrskey4
[root@localhost bin]# chmod 600 kgcrskey{1..4}
[root@localhost bin]# mongod -f /etc/mongod.conf   //重启4个实例//
[root@localhost bin]# mongod -f /etc/mongod2.conf
[root@localhost bin]# mongod -f /etc/mongod3.conf
[root@localhost bin]# mongod -f /etc/mongod4.conf
[root@localhost bin]# mongo --port 27017  //进入标准节点中//
kgcrs:PRIMARY> show dbs       //无法查看数据库//
kgcrs:PRIMARY> rs.status()   //无法查看复制集//
kgcrs:PRIMARY> use admin    //身份登录验证//
kgcrs:PRIMARY> db.auth("root","123")
kgcrs:PRIMARY> show dbs     //可以查看数据库//
admin   0.000GB
config  0.000GB
local   0.000GB
kgcrs:PRIMARY> rs.status()  //可以查看复制集//
"_id" : 0,
            "name" : "192.168.126.132:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",   
            "uptime" : 411,
"_id" : 1,
            "name" : "192.168.126.132:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",    
            "uptime" : 324,

            "_id" : 2,
            "name" : "192.168.126.132:27019",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 305,
"_id" : 3,
            "name" : "192.168.126.132:27020",
            "health" : 1,
            "state" : 7,
            "stateStr" : "ARBITER",
            "uptime" : 280,