MongoDB单机部署三节点副本集

MongoDB复制原理就是主节点记录在其上的所有操作oplog，从节点定期轮询主节点获取这些操作，然后对自己的数据副本执行这些操作，从而保证从节点的数据与主节点一致。

副本集特征：

1. N 个节点的集群
2. 任何节点可作为主节点
3. 所有写入操作都在主节点上
4. 自动故障转移
5. 自动恢复

副本集需要注意的地方：

1. 最小构成是：primary，secondary，arbiter，一般部署是：primary，2 secondary。
2. 成员数应该为奇数，如果为偶数的情况下添加arbiter，arbiter不保存数据，只投票。
3. 最大50 members，但是只能有 7 voting members，其他是non-voting members。

1.环境准备

192.168.1.121:27017作为主节点，

192.168.1.121:27018,192.168.1.121:27019作为两个副本节点

2.分别创建三个节点所需要的文件夹

mkdir /usr/mongoDB/rs{0,1,2}/data/db #存放三个节点数据文件
touch /usr/mongoDB/rs{0,1,2}/log/mongo.log #存放三个节点的日志

a.png

3.创建三个节点的配置文件

内容示例：

dbpath=/usr/mongoDB/rs0/data/db
logpath=/usr/mongoDB/rs0/log/mongo.log 
logappend=true
port=27017
fork=true
auth=false
bind_ip=192.168.1.121 
journal=true
quiet=true
replSet=upmsSet

b.png

4.分别启动三个节点（mongod命令位于mongodb的bin目录中）

mongod -f /rs0/mongodb.conf 
mongod -f /rs1/mongodb.conf 
mongod -f /rs2/mongodb.conf

可以查看 位于log目录下的日志

c.png

5.初始化副本集

任选一个节点登录，看到show dbs不可用，因为还没初始化副本集

d.png

使用

> use admin 
switched to db admin

定义副本集配置变量，这里的 _id:”upmsSet” 和上面配置文件的参数“ –replSet upmsSet” 要保持一样

>config= {_id:"upmsSet",members:[ 
{_id:0,host:"192.168.1.121:27017"}, 
{_id:1,host:"192.168.1.121:27018"}, 
{_id:2,host:"192.168.1.121:27019"}] 
}

初始化副本集配置

 > rs.initiate(config); 
{ "ok" : 1 }

e.png

查看集群节点状态：

> rs.status() 
{
    "set" : "upmsSet",
    "date" : ISODate("2019-02-28T05:40:07.400Z"),
    "myState" : 2,
    "term" : NumberLong(0),
    "syncingTo" : "",
    "syncSourceHost" : "",
    "syncSourceId" : -1,
    "heartbeatIntervalMillis" : NumberLong(2000),
    "optimes" : {
        "lastCommittedOpTime" : {
            "ts" : Timestamp(0, 0),
            "t" : NumberLong(-1)
        },
        "appliedOpTime" : {
            "ts" : Timestamp(1551332397, 1),
            "t" : NumberLong(-1)
        },
        "durableOpTime" : {
            "ts" : Timestamp(1551332397, 1),
            "t" : NumberLong(-1)
        }
    },
    "lastStableCheckpointTimestamp" : Timestamp(0, 0),
    "members" : [
        {
            "_id" : 0,
            "name" : "192.168.1.121:27017",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 353,
            "optime" : {
                "ts" : Timestamp(1551332397, 1),
                "t" : NumberLong(-1)
            },
            "optimeDate" : ISODate("2019-02-28T05:39:57Z"),
            "syncingTo" : "",
            "syncSourceHost" : "",
            "syncSourceId" : -1,
            "infoMessage" : "could not find member to sync from",
            "configVersion" : 1,
            "self" : true,
            "lastHeartbeatMessage" : ""
        },
        {
            "_id" : 1,
            "name" : "192.168.1.121:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 9,
            "optime" : {
                "ts" : Timestamp(1551332397, 1),
                "t" : NumberLong(-1)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1551332397, 1),
                "t" : NumberLong(-1)
            },
            "optimeDate" : ISODate("2019-02-28T05:39:57Z"),
            "optimeDurableDate" : ISODate("2019-02-28T05:39:57Z"),
            "lastHeartbeat" : ISODate("2019-02-28T05:40:07.203Z"),
            "lastHeartbeatRecv" : ISODate("2019-02-28T05:40:07.242Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "",
            "syncSourceHost" : "",
            "syncSourceId" : -1,
            "infoMessage" : "",
            "configVersion" : 1
        },
        {
            "_id" : 2,
            "name" : "192.168.1.121:27019",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 9,
            "optime" : {
                "ts" : Timestamp(1551332397, 1),
                "t" : NumberLong(-1)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1551332397, 1),
                "t" : NumberLong(-1)
            },
            "optimeDate" : ISODate("2019-02-28T05:39:57Z"),
            "optimeDurableDate" : ISODate("2019-02-28T05:39:57Z"),
            "lastHeartbeat" : ISODate("2019-02-28T05:40:07.204Z"),
            "lastHeartbeatRecv" : ISODate("2019-02-28T05:40:07.244Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "",
            "syncSourceHost" : "",
            "syncSourceId" : -1,
            "infoMessage" : "",
            "configVersion" : 1
        }
    ],
    "ok" : 1,
    "operationTime" : Timestamp(1551332397, 1),
    "$clusterTime" : {
        "clusterTime" : Timestamp(1551332397, 1),
        "signature" : {
            "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
            "keyId" : NumberLong(0)
        }
    }
}