如果只有一个节点或者使用Master-Slave模式,存在主机挂掉后“单点失效”的问题。通过使用Mongo DB副本集,可以提高容错性和可用性~~
Areplica setin MongoDB is a group of
mongod
processes that maintain the same data set. Replica sets provide redundancy and high availability
什么是副本集( Repilca Set )?
副本集在Mongo DB中就是一组mongod维护相同的数据集,副本集提供冗余和高可用~~
一个三个节点的副本集如下图所示:
本篇博文主要给出一个搭建三个节点Mongo DB副本集的示例,只要5个步骤即可~废话不说了,直接来战~~~
第一步 - 准备环境
准备三个虚拟机,其中一个用作Primary,另外两个用作Secondary。如上图展示的那样~
虚拟机信息如下:
Primary -172.xx.xx.107
Secondary -172.xx.xx.105和172.xx.xx.106
本文的虚拟机装的是CentOS 6.7 ~
第二步 - yum安装Mongo
本文使用yum install mongodb-org命令来安装。
如果遇到No package mongodb-org available.的问题,如:
- Loaded plugins: fastestmirror
- Setting up Install Process
- Loading mirror speeds from cached hostfile
- No package mongodb-org available.
- Error: Nothing to do
在/etc/yum.repos.d/目录下,创建一个mongodb.repo文件,指定MongoDB资源库即可。
使用vim /etc/yum.repos.d/mongodb.repo命令,创建并打开文件mongodb.repo,
- [mongodb-org-3.4]
- name=MongoDB Repository
- baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/3.4/x86_64/
- gpgcheck=1
- enabled=1
- gpgkey=https://www.mongodb.org/static/pgp/server-3.4.asc
然后,重新使用yum install mongodb-org命令安装即可。
@H_403_120@第三步 - 配置副本集
使用vim /etc/mongod.conf配置,每一台虚拟机上的Mongod配置文件。
在replication选项中添加oplogSizeMB 和 replSetName两个属性~
- replication:
- oplogSizeMB: 1024
- replSetName: wang
配置文件mongod.conf如下所示:
- # mongod.conf
- # for documentation of all options,see:
- # http://docs.mongodb.org/manual/reference/configuration-options/
- # where to write logging data.
- systemLog:
- destination: file
- logAppend: true
- 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
- # network interfaces
- net:
- port: 27017
- bindIp: 0.0.0.0 # Listen to local interface only,comment to listen on all interfaces.
- #security:
- #operationProfiling:
- replication:
- oplogSizeMB: 1024
- replSetName: wang
- #sharding:
- ## Enterprise-Only Options
- #auditLog:
- #snmp:
注意:
3台虚拟机,MongoDB配置文件mongod.conf中的replSetName名字要保持一致,
在本例中,replSetName的名字为wang,这个名字可以随便取~~
第四步 - 启动
配置好副本集之后,通过mongod --config /etc/mongod.conf命令启动三个虚拟机中的Mongo服务~,如:
- [root@dev04 mongodb]# mongod --config /etc/mongod.conf
- about to fork child process,waiting until server is ready for connections.
- forked process: 30799
- child process started successfully,parent exiting
因为107端口的虚拟机安装的MongoDB要用作Primary节点,所以,我们可以使用mongo命令来连接~
- [root@dev04 mongodb]# mongo
- MongoDB shell version v3.4.2
- connecting to: mongodb://127.0.0.1:27017
- MongoDB server version: 3.4.2
- Server has startup warnings:
- 2017-02-17T09:19:20.240+0800 I STORAGE [initandlisten]
- 2017-02-17T09:19:20.240+0800 I STORAGE [initandlisten] ** WARNING: Using the XFS filesystem is strongly recommended with the WiredTiger storage engine
- 2017-02-17T09:19:20.240+0800 I STORAGE [initandlisten] ** See http://dochub.mongodb.org/core/prodnotes-filesystem
- 2017-02-17T09:19:20.964+0800 I CONTROL [initandlisten]
- 2017-02-17T09:19:20.964+0800 I CONTROL [initandlisten] ** WARNING: Access control is not enabled for the database.
- 2017-02-17T09:19:20.964+0800 I CONTROL [initandlisten] ** Read and write access to data and configuration is unrestricted.
- 2017-02-17T09:19:20.964+0800 I CONTROL [initandlisten] ** WARNING: You are running this process as the root user,which is not recommended.
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten]
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten]
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten] ** We suggest setting it to 'never'
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten]
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten] ** We suggest setting it to 'never'
- 2017-02-17T09:19:20.965+0800 I CONTROL [initandlisten]
使用use admin,切换到时admin数据库,
- > use admin
- switched to db admin
然后通过config配置设置副本集节点成员~~
config={_id:"wang",members:[{_id:0,host:"172.xxx.xxx.107:27017"},{_id:1,host:"172.xxx.xxx.106:27017"},{_id:2,host:"172.xxx.xxx.105:27017"}]}
注:
_id:"wang",wang是副本集中取得名字。
members中添加每个副本集Mongod的_id和host信息
执行完上述信息,会出现如下信息:
- > config={_id:"wang",host:"172.xxx.xxx.105:27017"}]}
- {
- "_id" : "wang","members" : [
- {
- "_id" : 0,"host" : "172.xxx.xxx.107:27017"
- },{
- "_id" : 1,"host" : "172.xxx.xxx.106:27017"
- },{
- "_id" : 2,"host" : "172.xxx.xxx.105:27017"
- }
- ]
- }
- >
然后,执行配置初始化,看到{ "ok" : 1 },则表明初始化成功~
- > rs.initiate(config)
- { "ok" : 1 }
使用rs.status()查看副本节点状态~~
- wang:PRIMARY> rs.status()
- {
- "set" : "wang","date" : ISODate("2017-02-17T01:30:53.128Z"),"myState" : 1,"term" : NumberLong(1),"heartbeatIntervalMillis" : NumberLong(2000),"optimes" : {
- "lastCommittedOpTime" : {
- "ts" : Timestamp(1487295047,1),"t" : NumberLong(1)
- },"appliedOpTime" : {
- "ts" : Timestamp(1487295047,"durableOpTime" : {
- "ts" : Timestamp(1487295047,"t" : NumberLong(1)
- }
- },"name" : "172.xxx.xxx.107:27017","health" : 1,"state" : 1,"stateStr" : "PRIMARY","uptime" : 693,"optime" : {
- "ts" : Timestamp(1487295047,"t" : NumberLong(1)
- },"optimeDate" : ISODate("2017-02-17T01:30:47Z"),"infoMessage" : "could not find member to sync from","electionTime" : Timestamp(1487294966,"electionDate" : ISODate("2017-02-17T01:29:26Z"),"configVersion" : 1,"self" : true
- },"name" : "172.xxx.xxx.106:27017","state" : 2,"stateStr" : "SECONDARY","uptime" : 96,"optimeDurable" : {
- "ts" : Timestamp(1487295047,"optimeDurableDate" : ISODate("2017-02-17T01:30:47Z"),"lastHeartbeat" : ISODate("2017-02-17T01:30:52.708Z"),"lastHeartbeatRecv" : ISODate("2017-02-17T01:30:51.674Z"),"pingMs" : NumberLong(0),"syncingTo" : "172.xxx.xxx.107:27017","configVersion" : 1
- },"name" : "172.xxx.xxx.105:27017","lastHeartbeatRecv" : ISODate("2017-02-17T01:30:51.745Z"),"syncingTo" : "172.xxx.xxx.106:27017","configVersion" : 1
- }
- ],"ok" : 1
- }
- wang:PRIMARY>
从上图圈出来的信息可以看出,一个Primary 和两个Secondary的副本集已经完成~~~
第五步 - 验证
最后一步就是用来验证了,看看数据能否同步过来~~~
写的操作是在Primary节点上操作的。
在107节点上,创建一个messages的数据库,然后在message Collection中插入两条message。
- wang:PRIMARY> show dbs
- admin 0.000GB
- local 0.000GB
- wang:PRIMARY> use messages
- switched to db messages
- wang:PRIMARY> db.message.insert({"name":"This is a test message"})
- WriteResult({ "nInserted" : 1 })
- wang:PRIMARY> show dbs
- admin 0.000GB
- local 0.000GB
- messages 0.000GB
- wang:PRIMARY> db.message.insert({"name":"This is a test message111"})
- WriteResult({ "nInserted" : 1 })
- wang:PRIMARY>
通过可视化工具查看,Secondary节点105和106上是否可以同步Primary节点107上messages数据库的信息~~
详细信息如下:
从可视化工具的截图可以看出,两个Secondary节点105和106,与Primary节点107,拥有同样的数据集~~ 至此,Mongo DB副本集的环境搭建完成~~~