近期有同学问mongodb副本集难不难部署，我的回答是不难，很快，几分钟搞定，比mysql MHA简单的不止一点半点。 那么到底如何部署呢？请看下文。

1.  准备工作

1.1 下载软件

选择版本并下载mongodb的软件，注意操作系统版本等。本次我选用的是percona分支的mongodb 4.2.8版本搭建，操作系统为centos6

cd /usr/local/
wget  https://www.percona.com/downloads/percona-server-mongodb-LATEST/percona-server-mongodb-4.2.8-8/binary/tarball/percona-server-mongodb-4.2.8-8-centos6-x86_64.tar.gz
tar -zxvf  percona-server-mongodb-4.2.8-8-centos6-x86_64.tar.gz
ln -s percona-server-mongodb-4.2.8-8 mongodb

1.2  规划各节点角色

各节点角色如下

2  部署

2.1  创建各节点相关目录

创建数据目录、日志目录等相关目录

[root@m1 ~]# mkdir -p /data/mongodb/27017/{data,logs,tmp,etc,keyfile}
[root@m1 ~]# cd /data/mongodb/27017/
[root@m1 27017]# ll
总用量 20
drwxr-xr-x 2 root root 4096 8月   7 16:59 data
drwxr-xr-x 2 root root 4096 8月   7 16:59 etc
drwxr-xr-x 2 root root 4096 8月   7 16:59 keyfile
drwxr-xr-x 2 root root 4096 8月   7 16:59 logs
drwxr-xr-x 2 root root 4096 8月   7 16:59 tmp

2.2  配置文件

创建配置文件，并添加对应的配置信息，注意仲裁节点的端口

[root@m1 27017]# cd  /data/mongodb/27017/etc/
[root@m1 etc]# vim mongod.conf
添加如下内容

storage:
dbPath: /data/mongodb/27017/data
journal:
enabled: true
systemLog:
destination: file
logAppend: true
path: /data/mongodb/27017/logs/mongod.log
processManagement:
fork: true
pidFilePath: /data/mongodb/27017/tmp/mongod.pid
net:
port: 27017
bindIp: 0.0.0.0
replication:
  replSetName: "test1"                 # 副本集名称

2.3   启动各节点

以其中一个节点为例，其他节点修改对应配置文件即可

[root@m1 local]#  /usr/local/mongodb/bin/mongod   -f /data/mongodb/27017/etc/mongod.conf
about to fork child process, waiting until server is ready for connections.
forked process: 30019
child process started successfully, parent exiting

2.4  初始化副本集

初始化副本集，指定各节点id及角色，注意副本集的名称和配置文件里一致。

在任意节点执行如下语句

> use admin
switched to db admin
> rs.initiate( {
... _id: "test1",
... members: [
... { _id: 0, host: "192.168.128.208:27017" },
... { _id: 1, host: "192.168.128.209:27017" },
... { _id: 2, host: "192.168.128.209:28017",arbiterOnly:true }
... ] })
{
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1596792682, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1596792682, 1)
}

完成后可以查看各集群状态,如下，可见当前192.168.128.208:27017 为PRIMARY节点

test1:PRIMARY> rs.status()
{
"set" : "test1",
"date" : ISODate("2020-08-07T11:09:24.454Z"),
"myState" : 1,
"term" : NumberLong(1),
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"heartbeatIntervalMillis" : NumberLong(2000),
"majorityVoteCount" : 2,
"writeMajorityCount" : 2,
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1596798563, 1),
"t" : NumberLong(1)
},
"lastCommittedWallTime" : ISODate("2020-08-07T11:09:23.663Z"),
"readConcernMajorityOpTime" : {
"ts" : Timestamp(1596798563, 1),
"t" : NumberLong(1)
},
"readConcernMajorityWallTime" : ISODate("2020-08-07T11:09:23.663Z"),
"appliedOpTime" : {
"ts" : Timestamp(1596798563, 1),
"t" : NumberLong(1)
},
"durableOpTime" : {
"ts" : Timestamp(1596798563, 1),
"t" : NumberLong(1)
},
"lastAppliedWallTime" : ISODate("2020-08-07T11:09:23.663Z"),
"lastDurableWallTime" : ISODate("2020-08-07T11:09:23.663Z")
},
"lastStableRecoveryTimestamp" : Timestamp(1596798513, 1),
"lastStableCheckpointTimestamp" : Timestamp(1596798513, 1),
"electionCandidateMetrics" : {
"lastElectionReason" : "electionTimeout",
"lastElectionDate" : ISODate("2020-08-07T09:31:33.409Z"),
"electionTerm" : NumberLong(1),
"lastCommittedOpTimeAtElection" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"lastSeenOpTimeAtElection" : {
"ts" : Timestamp(1596792682, 1),
"t" : NumberLong(-1)
},
"numVotesNeeded" : 2,
"priorityAtElection" : 1,
"electionTimeoutMillis" : NumberLong(10000),
"numCatchUpOps" : NumberLong(0),
"newTermStartDate" : ISODate("2020-08-07T09:31:33.444Z"),
"wMajorityWriteAvailabilityDate" : ISODate("2020-08-07T09:31:34.050Z")
},
"members" : [
{
"_id" : 0,
"name" : "192.168.128.208:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 5950,
"optime" : {
"ts" : Timestamp(1596798563, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2020-08-07T11:09:23Z"),
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1596792693, 1),
"electionDate" : ISODate("2020-08-07T09:31:33Z"),
"configVersion" : 1,
"se
56c
lf" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "192.168.128.209:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 5882,
"optime" : {
"ts" : Timestamp(1596798563, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1596798563, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2020-08-07T11:09:23Z"),
"optimeDurableDate" : ISODate("2020-08-07T11:09:23Z"),
"lastHeartbeat" : ISODate("2020-08-07T11:09:23.672Z"),
"lastHeartbeatRecv" : ISODate("2020-08-07T11:09:22.804Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "192.168.128.208:27017",
"syncSourceHost" : "192.168.128.208:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 1
},
{
"_id" : 2,
"name" : "192.168.128.209:28017",
"health" : 1,
"state" : 7,
"stateStr" : "ARBITER",
"uptime" : 5882,
"lastHeartbeat" : ISODate("2020-08-07T11:09:23.672Z"),
"lastHeartbeatRecv" : ISODate("2020-08-07T11:09:22.952Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"configVersion" : 1
}
],
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1596798563, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1596798563, 1)
}
test1:PRIMARY>

3  修改为认证模式

为考虑安全性等，需要开启认证模式（需要通过用户名/密码方式登录）

3.1 创建用户

创建超级管理员账号

test1:PRIMARY> db.createUser({user: "root", pwd: "Root#123", roles: [{role: "root", db: "admin"}]})
Successfully added user: {
"user" : "root",
"roles" : [
{
"role" : "root",
"db" : "admin"
}
]
}

3.2  创建key文件

在主库上执行脚本生成key文件，然后将结拷贝到另外2个节点

[root@m1 mongodb]# cd /data/mongodb/27017/keyfile/
[root@m1 keyfile]# openssl rand -base64 756 > mongo.key
[root@m1 keyfile]# chmod 600 mongo.key   # 必须修改为600权限，否则无法启动

以上完成后，将文件复制到另外2个节点

3.3  修改配置文件

配置文件中 添加如下内容，注意不同节点的文件路径

security:
authorization: enabled
clusterAuthMode: keyFile
keyFile: /data/mongodb/27017/keyfile/mongo.key

3.4  重启后并用认证模式登陆

# 关闭mongodb
[root@m1 keyfile]#  /usr/local/mongodb/bin/mongod   -f /data/mongodb/27017/etc/mongod.conf  -shutdown
killing process with pid: 30675
# 启动mongodb
[root@m1 keyfile]#  /usr/local/mongodb/bin/mongod   -f /data/mongodb/27017/etc/mongod.conf about to fork child process, waiting until server is ready for connections.
forked process: 2430

child process started successfully, parent exiting

#  认证模式登陆
[root@m1 keyfile]#
[root@m1 keyfile]# /usr/local/mongodb/bin/mongo   -u root  -p 'Root#123'  --authenticationDatabase admin

至此，mongodb 副本集搭建完毕，你会了吗？

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