MongoDB的集群模式--Replica Set

一、replica set 集群分为两种架构：

• 奇数个节点构成replica set，所有节点拥有数据集。最小架构: 1个primary节点，2个secondary节点

• 偶数个节点 + 一个仲裁节点 构成的replica set，节点拥有数据集，仲裁节点仅参与仲裁选举出primary节点。 最小架构：1个primary节点，1个secondary节点，1个arbiter节点
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接下来就以3台服务器为例，部署具有仲裁的框架。

ip地址	操作系统版本	mongodb版本	端口	功能
10.10.18.10	centos7.5	4.0	27017	primary
10.10.18.11	centos7.5	4.0	27017	secondary
10.10.18.12	centos7.5	4.0	27017	arbiter

二、安装部署（请访问 "mongodb安装"）

primary的配置文件：

systemlog:
   destination: file
   path: "/data/mongodb/log/mongod.log"
   logappend: true
storage:
   dbpath: "/data/mongodb/data"
   journal:
      enabled: true
   wiredtiger:
      engineconfig:
        cachesizegb: 2
processmanagement:
   fork: true
   pidfilepath: "/data/mongodb/pid/m.pid"
net:
   bindip: 10.10.18.10
   port: 27017
replication:
   replsetname: "rs0"

secondary的配置文件

systemlog:
   destination: file
   path: "/data/mongodb/log/mongod.log"
   logappend: true
storage:
   dbpath: "/data/mongodb/data"
   journal:
      enabled: true
   wiredtiger:
      engineconfig:
        cachesizegb: 2
processmanagement:
   fork: true
   pidfilepath: "/data/mongodb/pid/m.pid"
net:
   bindip: 10.10.18.11
   port: 27017
replication:
   replsetname: "rs0"

arbiter的配置文件

systemlog:
   destination: file
   path: "/data/mongodb/log/mongod.log"
   logappend: true
storage:
   dbpath: "/data/mongodb/data"
   journal:
      enabled: true
   wiredtiger:
      engineconfig:
        cachesizegb: 2
processmanagement:
   fork: true
   pidfilepath: "/data/mongodb/pid/m.pid"
net:
   bindip: 10.10.18.12
   port: 27017
replication:
   replsetname: "rs0"

启动三台服务器上的mongdb

mongod -f /data/mongodb/mongod.conf

三、配置replica set

登录三台服务器中任意一台，登录mongo

mongo --host 10.10.18.10

>cfg={ _id:"rs0",members:[{_id:0,host:'10.10.18.10:27017',priority:1},{_id:1,host:'10.10.18.11:27017',priority:1},{_id:2,host:'10.10.18.12:27017',arbiteronly:true}] };

>rs.initiate(cfg)

查看replica set配置

> rs.conf()

{
"_id" : "rs0",
"version" : 1,
"protocolversion" : numberlong(1),
"writeconcernmajorityjournaldefault" : true,
"members" : [
{
"_id" : 0,
"host" : "10.10.18.10:27017",
"arbiteronly" : false,
"buildindexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {

},
"slavedelay" : numberlong(0),
"votes" : 1
},
{
"_id" : 1,
"host" : "10.10.18.11:27017",
"arbiteronly" : false,
"buildindexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {

},
"slavedelay" : numberlong(0),
"votes" : 1
},
{
"_id" : 2,
"host" : "10.10.18.12:27017",
"arbiteronly" : true,
"buildindexes" : true,
"hidden" : false,
"priority" : 0,
"tags" : {

},
"slavedelay" : numberlong(0),
"votes" : 1
}
],
"settings" : {
"chainingallowed" : true,
"heartbeatintervalmillis" : 2000,
"heartbeattimeoutsecs" : 10,
"electiontimeoutmillis" : 10000,
"catchuptimeoutmillis" : -1,
"catchuptakeoverdelaymillis" : 30000,
"getlasterrormodes" : {

},
"getlasterrordefaults" : {
"w" : 1,
"wtimeout" : 0
},
"replicasetid" : objectid("5cff76e5e57e23a5bc7054e2")
}
}

四、验证replica set

在primary中插入数据

rs0:primary>  show dbs
admin   0.000gb
config  0.000gb
local   0.000gb
rs0:primary> db.users.insertone(
... {
... name:"sue",
... age: 26,
... status:"pending"
... })
{
        "acknowledged" : true,
        "insertedid" : objectid("5cff79e8993e70290a081d04")
}

rs0:primary> db.users.find()
{ "_id" : objectid("5cff79e8993e70290a081d04"), "name" : "sue", "age" : 26, "status" : "pending" }

在secondary中，默认是不允许读

rs0:secondary> db.users.find()
error: error: {
        "operationtime" : timestamp(1560247181, 1),
        "ok" : 0,
        "errmsg" : "not master and slaveok=false",
        "code" : 13435,
        "codename" : "notmasternoslaveok",
        "$clustertime" : {
                "clustertime" : timestamp(1560247181, 1),
                "signature" : {
                        "hash" : bindata(0,"aaaaaaaaaaaaaaaaaaaaaaaaaaa="),
                        "keyid" : numberlong(0)
                }
        }
}

五、故障模拟

停止primary上的mongo进程，在secondary上登录mongo查看

mongo --host 10.10.18.11


rs0:primary> db.users.find()
{ "_id" : objectid("5cff79e8993e70290a081d04"), "name" : "sue", "age" : 26, "status" : "pending" }

发现原secondary变成primary，并且可以进行查询。

开启原primary服务器上的mongo进程，该服务器变成了secondary。