mongoDB Replica Set Actual Warfare

background

Features of a mongoDB single server:

- Risk of data loss
 - Single server cannot be highly available

Features of the mongoDB replica set:

-High Availability Architecture to Prevent Data Loss
 - Keep multiple replicas synchronized and consistent
 - The mongodb replica set switches automatically when there is a problem

Preparation for actual combat

Replica Set Environment Configuration

• At least three servers in a production environment

  Machine IP
  host name
  mongo port
  Profile Path
  role
  192.168.56.11
  centos7-node1
  27017
  /data/mongodb/27017/mongodb.conf

192.168.56.12
centos7-node2
27018
/data/mongodb/27018/mongodb.conf

192.168.56.13
centos7-node3
27019
/data/mongodb/27019/mongodb.conf

• mongo software: https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-4.0.17.tgz
• configuration file
• The single-node configuration is as follows:

[root@centos7-node1 ~]# cd /opt/ && wget https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-4.0.17.tgz
[root@centos7-node1 ~]# tar xf /opt/mongodb-linux-x86_64-4.0.17.tgz
[root@centos7-node1 ~]# mv mongodb-linux-x86_64-4.0.17/ /usr/local/mongodb
[root@centos7-node1 ~]# mkdir -pv /data/mongodb/27017
[root@centos7-node1 ~]# vim /data/mongodb/27017/mongodb.conf 
systemLog:
  destination: file
  logAppend: true
  path: /data/mongodb/27017/mongodb.log
storage:
  dbPath: /data/mongodb/27017/
  journal:
    enabled: true
processManagement:
  fork: true
net:
  port: 27017
  bindIp: 0.0.0.0
replication:
  replSetName: copySet
[root@centos7-node1 ~]# /usr/local/mongodb/bin/mongod -f /data/mongodb/27017/mongodb.conf    #Start Services
[root@centos7-node1 ~]# netstat -tanlp | grep mongo   #Process Viewing

• The configuration of other nodes only needs to modify the port, then modify the configuration file, log directory, and the following is the service start command

[root@centos7-node2 ~]# /usr/local/mongodb/bin/mongod -f /data/mongodb/27018/mongodb.conf 
[root@centos7-node3 ~]# /usr/local/mongodb/bin/mongod -f /data/mongodb/27019/mongodb.conf 

Replica Set Initialization

Notes:

• Sign in to a mongdb at random

[root@centos7-node1 27017]# /usr/local/mongodb/bin/mongo localhost:27017   #Log on to the first station
> config={
 _id: "copySet",members:[
  {_id:0,host:"192.168.56.11:27017"},
  {_id:1,host:"192.168.56.12:27018"},
  {_id:2,host:"192.168.56.13:27019"},
 ]
}
> rs.initiate(config)
> rs.status()

Test replica set data synchronization

• Inserting data can only be done from Primary, and Secondary can only read data

copySet:PRIMARY> use test
copySet:PRIMARY> db.myuser.insert({userid:1})

• Query data read from library: ok if no exception

copySet:SECONDARY> rs.slaveOk()
copySet:SECONDARY> show dbs
copySet:SECONDARY> use test
copySet:SECONDARY> db.myuser.find()
copySet:SECONDARY> rs.printSlaveReplicationInfo()    #View Delay From Library

Automatic switching of replica sets

• When primary hangs up, one of them will be elected as primary
• If there is only one instance left in the cluster, an exception will occur: (if there is only one)

# Log on to primary and then stop service
copySet:PRIMARY> use admin
copySet:PRIMARY> db.shutdownServer()

The remaining two will elect primary nodes

Specify primary by priority

• Default priority weights are all 1
• primary in the replica set is the most weighted one selected
• The priority weight is set as follows [at the primary node]:

copySet:PRIMARY> conf = rs.config()
copySet:PRIMARY> conf.members[0].priority = 5
copySet:PRIMARY> conf.members[1].priority = 4
copySet:PRIMARY> conf.members[2].priority = 3
copySet:PRIMARY> rs.reconfig(conf)

Scaling of replica sets

• The mongoDB replica set is very scalable, and it is easy to add and delete instances to the replica set
• Add replica set data to automatically synchronize
• Prepare a new machine and copy, set port and configuration file to 27020, and copy name
• Adding a replica set to the cluster is done on primary as follows

[root@centos7-node4 ~]# vim /data/mongodb/27020/mongodb.conf 
systemLog:
  destination: file
  logAppend: true
  path: /data/mongodb/27020/mongodb.log
storage:
  dbPath: /data/mongodb/27020/
  journal:
    enabled: true
processManagement:
  fork: true
net:
  port: 27020
  bindIp: 0.0.0.0
replication:
  replSetName: copySet
[root@centos7-node4 ~]# /usr/local/mongodb/bin/mongod -f /data/mongodb/27020/mongodb.conf    #Start a new node
copySet:PRIMARY> rs.add('192.168.56.14:27020')      #The primary node joins the new node and the data synchronizes automatically
copySet:PRIMARY> rs.remove('192.168.56.14:27020')   #Remove secondary

Backup and recovery of mongoDB

• Single server, must backup

• The backup and restore tools are:

  • mongodump: backup
  • mongostore: restore
• Backup of replica sets is done on primary

Full backup and restore

~]# mkdir /data/mongodbbacku
~]# /usr/local/mongodb/bin/mongodump -h 127.0.0.1:27020 -o /data/mongodbbackup/     #Backup Data
~]# /usr/local/mongodb/bin/mongorestore -h 127.0.0.1 --port 27021 /data/mongodbbackup/             #Restore data