Redis learning - master-slave replication, sentinel

master-slave replication

Official documentation: https://redis.io/topics/replication

Master-slave replication in Redis, that is, the Master-Slave model, has the following characteristics

　　Master can have multiple slaves

　　Multiple slaves can not only connect to the same master, but also connect to other slaves

　　Master-slave replication will not block the master. When synchronizing data, the master can continue to process client requests

　　Provides system scalability

Master-slave replication process:

　　The slave establishes a connection with the master and sends a sync synchronization command

　　The master starts a background process to keep data snapshots in the file, and the master master process starts to collect new write commands and cache them

　　After saving in the background, send the file to the slave

　　slave saves the file to the hard disk

Master-slave replication configuration:

　　Configure 3 redis, 1master2slave

　　Use scp -r redis3.2_1/ sloveip:/ copy directory to copy the redis installed on the master to the slave

　　Modify the port number of the master slave in the configuration file

　　Modify the slaveof of the slave to the ip address port number of the host

　　Start these three redis services respectively

　　You can see that the master and slave have been started

　　Since it is simulated on the same machine, the port number must be specified to start the client

　　After startup, check the information in info, you can see that the master and slave have succeeded

　　View the slave and print the following information

　　When the master writes data, the slave can read it

sentinel

　　Sentinel can monitor the running status of the redis system. The main functions are:

　　　　Monitor whether the master database and slave database are running normally

　　　　When the primary database fails, the secondary database can be automatically replaced with the primary database to achieve automatic switching

　　Configuration (configured on slave1)

　　Copy the sentinel.conf file under the installed redis3.2_1 file to the folder where the configuration file is stored　

　　Then enter the sentinel.conf file and configure the directory

　　Configuration name, master node ip, port, number of voting elections (1 means that there is a slave node that thinks the master node is down and the master node is down)