第六章 MongoDB副本集搭建

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本文介绍了MongoDB副本集的搭建过程，包括在CentOS 7环境下准备三台安装MongoDB的主机，关闭防火墙和SElinux，创建数据与日志目录，修改配置文件并初始化。还展示了在主节点添加数据后从节点的同步情况，以及模拟故障时节点的变化。

第六章 MongoDB 副本集搭建

搭建副本集群
在主节点添加数据，查看从节点
kill一个mongod实例，模拟故障，查看选举

1.搭建副本集群

环境准备：操作环境：CentOS 7。需要三台安装MongoBD的主机。安装移步至：MongoDB安装与使用

host1：192.168.195.3
host2: 192.168.195.4
host3: 192.168.195.5

关闭Linux防火墙和SElinux

systemctl stop firewalld.service # 关闭防火墙
systemctl disable firewalld.service # 禁止开机启动
firewall-cmd --state # 查看防火墙状态

# 永久关闭Selinux 设置后需要重启
vim /etc/selinux/config

SELINUX=disabled

给每个mongod实例创建数据目录和日志目录

mkdir -p /opt/local/mongodb/data
mkdir -p /opt/local/mongodb/conf

修改mongod.conf配置文件

vim /opt/local/mongodb/conf/mongod.conf

systemLog:
  destination: file
  logAppend: true
  path: /opt/local/mongodb/log/mongod.log

storage:
  dbPath: /opt/local/mongodb/data
  journal:
    enabled: true
    
processManagement:
  fork: true  
  pidFilePath: /opt/local/mongodb/mongod.pid  
  timeZoneInfo: /usr/share/zoneinfo

net:
  port: 27017
  bindIp: 0.0.0.0 # 这里所有ip地址都可以访问

replication:
  replSetName: "rs0"

启动三台mongod实例，登录到其中一个mongod实例，执行初始化

# 启动mongod服务
/opt/local/mongodb/bin/mongod -f /opt/local/mongodb/conf/mongod.conf

# 连接mongod服务
/opt/local/mongodb/bin/mongo -p 27017

# 初始化 _id是副本集群名字
rs.initiate( {
   _id : "rs0",
   members: [
      { _id: 0, host: "192.168.195.3:27017" },
      { _id: 1, host: "192.168.195.4:27017" },
      { _id: 2, host: "192.168.195.5:27017" }
   ]
})

查看副本集群的配置情况

rs.conf()

{
        "_id" : "rs0",
        "version" : 1,
        "protocolVersion" : NumberLong(1),
        "writeConcernMajorityJournalDefault" : true,
        "members" : [
                {
                        "_id" : 0,
                        "host" : "192.168.195.3:27017",
                        "arbiterOnly" : false,
                        "buildIndexes" : true,
                        "hidden" : false,
                        "priority" : 1,
                        "tags" : {
                                
                        },
                        "slaveDelay" : NumberLong(0),
                        "votes" : 1
                },
                {
                        "_id" : 1,
                        "host" : "192.168.195.4:27017",
                        "arbiterOnly" : false,
                        "buildIndexes" : true,
                        "hidden" : false,
                        "priority" : 1,
                        "tags" : {
                                
                        },
                        "slaveDelay" : NumberLong(0),
                        "votes" : 1
                },
                {
                        "_id" : 2,
                        "host" : "192.168.195.5:27017",
                        "arbiterOnly" : false,
                        "buildIndexes" : true,
                        "hidden" : false,
                        "priority" : 1,
                        "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("5f9eb1a81d83200f367912d7")
        }
}

2.在主节点添加数据，查看从节点

登录到从节点 (secondary) 查看 student 集合数据，此时并没有 student 集合

# secondary 节点默认不允许读，需要`rs.slaveOk()`设置可读
rs.slaveOk();

use test;
db.student.find({})

在主节点(primary)添加student集合

db.student.insertOne({
    name: "Tome",
    age: 20,
    address: "nanjing"
})

在 secondary 节点上查看 student 集合就能看到从 primary 节点同步过来的数据了

db.student.find({})

{ "_id" : ObjectId("5f9eb62d9a01685fb407a5bc"), "name" : "Tome", "age" : 20, "address" : "nanjing" }

3.模拟故障

ps -aux | grep mongod

root      36483  1.4 10.4 1943052 103928 ?      Sl   07:52   0:28 ./bin/mongod -f ./conf/mongodb.conf
root      70708  0.0  0.0 112824   976 pts/0    R+   08:24   0:00 grep --color=auto mongod

kill -9 36483