5步搞定CentOS6.7上MongoDB副本集搭建

孟君

发布于 2019-08-26 16:59:53

6000

发布于 2019-08-26 16:59:53

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。

A replica set in 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MongoDB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。

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",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"}]}
{
  "_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, 1),
      "t" : NumberLong(1)
    },
    "durableOpTime" : {
      "ts" : Timestamp(1487295047, 1),
      "t" : NumberLong(1)
    }
  },
  "members" : [
    {
      "_id" : 0,
      "name" : "172.xxx.xxx.107:27017",
      "health" : 1,
      "state" : 1,
      "stateStr" : "PRIMARY",
      "uptime" : 693,
      "optime" : {
        "ts" : Timestamp(1487295047, 1),
        "t" : NumberLong(1)
      },
      "optimeDate" : ISODate("2017-02-17T01:30:47Z"),
      "infoMessage" : "could not find member to sync from",
      "electionTime" : Timestamp(1487294966, 1),
      "electionDate" : ISODate("2017-02-17T01:29:26Z"),
      "configVersion" : 1,
      "self" : true
    },
    {
      "_id" : 1,
      "name" : "172.xxx.xxx.106:27017",
      "health" : 1,
      "state" : 2,
      "stateStr" : "SECONDARY",
      "uptime" : 96,
      "optime" : {
        "ts" : Timestamp(1487295047, 1),
        "t" : NumberLong(1)
      },
      "optimeDurable" : {
        "ts" : Timestamp(1487295047, 1),
        "t" : NumberLong(1)
      },
      "optimeDate" : ISODate("2017-02-17T01:30:47Z"),
      "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
    },
    {
      "_id" : 2,
      "name" : "172.xxx.xxx.105:27017",
      "health" : 1,
      "state" : 2,
      "stateStr" : "SECONDARY",
      "uptime" : 96,
      "optime" : {
        "ts" : Timestamp(1487295047, 1),
        "t" : NumberLong(1)
      },
      "optimeDurable" : {
        "ts" : Timestamp(1487295047, 1),
        "t" : NumberLong(1)
      },
      "optimeDate" : ISODate("2017-02-17T01:30:47Z"),
      "optimeDurableDate" : ISODate("2017-02-17T01:30:47Z"),
      "lastHeartbeat" : ISODate("2017-02-17T01:30:52.708Z"),
      "lastHeartbeatRecv" : ISODate("2017-02-17T01:30:51.745Z"),
      "pingMs" : NumberLong(0),
      "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~~