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MongoDB高可用方案之副本集(Replica Set)

时间:2018-09-30 16:44:26      阅读:224      评论:0      收藏:0      [点我收藏+]

标签:iptable   primary   master   .sh   14.04   eset   1.3   iat   mkdir   

一、介绍

Replicat Set比起传统的Master - Slave结构而言,应用场景更加多,也有了自动failover的能力

二、副本集结构图(参考:https://www.linuxidc.com/Linux/2017-03/142379.htm)

技术分享图片

类似于“MySQL中1主2从+mha_manager”的结构。

Replication通过Oplog实现语句复现

技术分享图片

三、副本集成员的属性

Replication通过Oplog实现语句复现
分别为Primary、Secondary(Secondaries)
Primary负责处理所有的write请求,并记录到oplog(operation log)中。
Secondary负责复制oplog并应用这些write请求到他们自己的数据集中。(有一些类似于MySQL Replication)

所有的副本集都可以处理读操作,但是需要设置。

最小化的副本集配置建议有三个成员:
1个Primary + 2个Secondary
或者
1个Primary + 1个Secondary + 1个Arbiter(仲裁者)

四、Arbiter和选举机制

Arbiter可以作为副本集的一部分,但它不是一个数据副本,故它不会成为Primary。
Arbiter在Primary不可用的时候,作为一个选举的角色存在。
如果Arbiter不存在,Primary挂掉的情况下,剩下的两个Secondary则也会进行选举。

在1个Primary + 2个Secondary的情况下,failover如下:

技术分享图片

五、搭建

1、实验环境

192.168.1.34(Primary)
192.168.1.35(Secondary1)
192.168.1.36(Secondary2)
192.168.1.37(Arbiter)

2、安装mongodb并启动

先在三台安装mongodb, 先关闭防火墙

service iptables stop

在三台机器分别创建对应目录并启动mongodb

# mkdir -p /data/mongo_replset
#./mongod --dbpath=/data/mongo_replset --logpath=/data/mongo_replset/mongo.log --fork --replSet=first_replset

3、配置副本集

登录192.168.1.34(Primary)的mongo shell

# ./mongo
> use admin
switched to db admin
输入
> cnf = {_id:"first_replset", members:[
...         {_id:1, host:"192.168.1.34:27017"},
...         {_id:2, host:"192.168.1.35:27017"},
...         {_id:3, host:"192.168.1.36:27017"},
...         ]
...     }
输出:
{
    "_id" : "first_replset",
    "members" : [
        {
            "_id" : 1,
            "host" : "192.168.1.34:27017"
        },
        {
            "_id" : 2,
            "host" : "192.168.1.35:27017"
        },
        {
            "_id" : 3,
            "host" : "192.168.1.36:27017"
        }
    ]
}

初始化配置:

>  rs.initiate(cnf);
{ "ok" : 1 }
first_replset:OTHER> 
first_replset:PRIMARY> 
first_replset:PRIMARY>

此时可以发现该mongodb实例已经成为PRIMARY了。

可以查看下这个副本集的各个成员的状态:

first_replset:PRIMARY> rs.status();
{
    "set" : "first_replset",
    "date" : ISODate("2018-01-03T06:37:10.559Z"),
    "myState" : 1,
    "members" : [
        {
            "_id" : 1,
            "name" : "192.168.1.34:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 599,
            "optime" : Timestamp(1514961357, 1),
            "optimeDate" : ISODate("2018-01-03T06:35:57Z"),
            "electionTime" : Timestamp(1514961361, 1),
            "electionDate" : ISODate("2018-01-03T06:36:01Z"),
            "configVersion" : 1,
            "self" : true
        },
        {
            "_id" : 2,
            "name" : "192.168.1.35:27017",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 73,
            "optime" : Timestamp(1514961357, 1),
            "optimeDate" : ISODate("2018-01-03T06:35:57Z"),
            "lastHeartbeat" : ISODate("2018-01-03T06:37:09.308Z"),
            "lastHeartbeatRecv" : ISODate("2018-01-03T06:37:09.316Z"),
            "pingMs" : 1,
            "lastHeartbeatMessage" : "could not find member to sync from",
            "configVersion" : 1
        },
        {
            "_id" : 3,
            "name" : "192.168.1.36:27017",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 73,
            "optime" : Timestamp(1514961357, 1),
            "optimeDate" : ISODate("2018-01-03T06:35:57Z"),
            "lastHeartbeat" : ISODate("2018-01-03T06:37:09.306Z"),
            "lastHeartbeatRecv" : ISODate("2018-01-03T06:37:09.313Z"),
            "pingMs" : 1,
            "lastHeartbeatMessage" : "could not find member to sync from",
            "configVersion" : 1
        }
    ],
    "ok" : 1
}

4、副本集复制状态测试

在PRIMARY上insert:

# ./mongo 127.0.0.1/test
first_replset:PRIMARY> db.test_table.insert({"id": 1})
WriteResult({ "nInserted" : 1 })
first_replset:PRIMARY> db.test_table.find()
{ "_id" : ObjectId("5a4c7b44ecb269292f0de224"), "id" : 1 }

在35、36任意SECONDARY上查询:

同master - slave结构一样,默认SECONDARY是不可读的,需要执行rs.slaveOk()。

first_replset:SECONDARY> rs.slaveOk()
first_replset:SECONDARY> db.test_table.find()
{ "_id" : ObjectId("5a4c7b44ecb269292f0de224"), "id" : 1 }

5、failover测试

此时情况:
192.168.1.34(Primary)
192.168.1.35(Secondary)
192.168.1.36(Secondary)

停掉PRIAMRY:

first_replset:PRIMARY> use admin
switched to db admin
first_replset:PRIMARY> db.shutdownServer()
2018-01-03T14:46:14.048+0800 I NETWORK  DBClientCursor::init call() failed
server should be down...
2018-01-03T14:46:14.052+0800 I NETWORK  trying reconnect to 127.0.0.1:27017 (127.0.0.1) failed
2018-01-03T14:46:14.052+0800 I NETWORK  reconnect 127.0.0.1:27017 (127.0.0.1) ok
2018-01-03T14:46:14.053+0800 I NETWORK  DBClientCursor::init call() failed
2018-01-03T14:46:14.056+0800 I NETWORK  trying reconnect to 127.0.0.1:27017 (127.0.0.1) failed
2018-01-03T14:46:14.056+0800 I NETWORK  reconnect 127.0.0.1:27017 (127.0.0.1) ok
2018-01-03T14:46:14.397+0800 I NETWORK  Socket recv() errno:104 Connection reset by peer 127.0.0.1:27017
2018-01-03T14:46:14.397+0800 I NETWORK  SocketException: remote: 127.0.0.1:27017 error: 9001 socket exception [RECV_ERROR] server [127.0.0.1:27017] 
2018-01-03T14:46:14.397+0800 I NETWORK  DBClientCursor::init call() failed

(原SECONDARY)35上查到,此时35已经为PRIMARY了

first_replset:SECONDARY> 
first_replset:PRIMARY> rs.status()
{
    "set" : "first_replset",
    "date" : ISODate("2018-01-03T06:47:14.289Z"),
    "myState" : 1,
    "members" : [
        {
            "_id" : 1,
            "name" : "192.168.1.34:27017",
            "health" : 0,
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "optime" : Timestamp(0, 0),
            "optimeDate" : ISODate("1970-01-01T00:00:00Z"),
            "lastHeartbeat" : ISODate("2018-01-03T06:47:14.034Z"),
            "lastHeartbeatRecv" : ISODate("2018-01-03T06:46:13.934Z"),
            "pingMs" : 0,
            "lastHeartbeatMessage" : "Failed attempt to connect to 192.168.1.34:27017; couldn‘t connect to server 192.168.1.34:27017 (192.168.1.34), connection attempt failed",
            "configVersion" : -1
        },
        {
            "_id" : 2,
            "name" : "192.168.1.35:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 1180,
            "optime" : Timestamp(1514961732, 2),
            "optimeDate" : ISODate("2018-01-03T06:42:12Z"),
            "electionTime" : Timestamp(1514961976, 1),
            "electionDate" : ISODate("2018-01-03T06:46:16Z"),
            "configVersion" : 1,
            "self" : true
        },
        {
            "_id" : 3,
            "name" : "192.168.1.36:27017",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 676,
            "optime" : Timestamp(1514961732, 2),
            "optimeDate" : ISODate("2018-01-03T06:42:12Z"),
            "lastHeartbeat" : ISODate("2018-01-03T06:47:13.997Z"),
            "lastHeartbeatRecv" : ISODate("2018-01-03T06:47:13.995Z"),
            "pingMs" : 0,
            "configVersion" : 1
        }
    ],
    "ok" : 1
}

6、在副本集中添加一个属性为Arbiter的成员

当然此处只做添加实践,实际上并不建议在Secondary-Primary-Secondary的结构上再多一个Arbiter成员形成偶数个节点。
在192.168.1.37上启动一个mongod实例:

# mkdir -p /data/arb
# ./mongod --dbpath=/data/arb/ --logpath=/data/arb/mongo.log --fork --replSet=first_replset

在failover后的PRIMARY节点添加Arbiter

first_replset:PRIMARY> rs.addArb("192.168.1.37:27017")
{ "ok" : 1 }
first_replset:PRIMARY> rs.status()
{
            "_id" : 4,
            "name" : "192.168.1.37:27017",
            "health" : 1,
            "state" : 7,
            "stateStr" : "ARBITER",
            "uptime" : 82,
            "lastHeartbeat" : ISODate("2018-01-03T07:16:14.872Z"),
            "lastHeartbeatRecv" : ISODate("2018-01-03T07:16:15.497Z"),
            "pingMs" : 1,
            "configVersion" : 2
        }
    ],
    "ok" : 1

此时回到arbiter的mongo shell,发现正如文档所说,arbiter是不会存有副本集中数据的。

first_replset:ARBITER> rs.slaveOk()
first_replset:ARBITER> use test;
switched to db test
first_replset:ARBITER> show tables;
first_replset:ARBITER> db.test_table.find();
Error: error: {
    "$err" : "not master or secondary; cannot currently read from this replSet member",
    "code" : 13436
}

 

MongoDB高可用方案之副本集(Replica Set)

标签:iptable   primary   master   .sh   14.04   eset   1.3   iat   mkdir   

原文地址:https://www.cnblogs.com/guantou1992/p/9729616.html

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