Redis master-slave replication & sentinel mode

1.1 What is master-slave replication

         After the master database data is updated, according to the configuration and strategy , Auto sync to slave Library （ Backup machine ） Of master/slaver Mechanism ,master( Main library ) Write first ,slave( Slave Library ) Mainly reading .

1.2 The role of master-slave replication

        Read / write separation ： master Write first ,slave Mainly reading .

        disaster recovery ： because slaves The data of master Copy of , Whether it's master still slaves Data can be effectively recovered after downtime .

1.3 Environmental preparation

 1.3.1 Copy three copies redis Configuration file for

         They can be named redis-6379.conf 、redis-6380.conf、redis-6381.conf
        cd  /usr/local/bin/tlconfig
        cp redis.conf redis-6379.conf
        cp redis.conf redis-6380.conf
        cp redis.conf redis-6381.conf

 1.3.2 Set up guards

                daemonize  yes

 1.3.3 Set port

                 Three configuration files set ports respectively
                        port 6379,port 6380 and port 6381   We put 6379 As the master ,6380 and 6381 As from

                Set up pid

                pid The file paths are configured as

                        pidfile /var/run/redis_6379.pid,

                        pidfile /var/run/redis_6380.pid

                        pidfile /var/run/redis_6381.pid

                Set up log
                        log The names are configured as
                        logfile "6379.log",
                        logfile "6380.log"
                        logfile "6381.log"

                Set up db
                        db The file names are configured as

                                dbfilename dump6379.rdb

                                dbfilename dump6380.rdb

                                dbfilename dump6381.rdb

        1.4 start-up  

                 Separate use redis-6379.conf、redis-6380.conf、redis-6381.conf To start three services
                        redis-server tlconfig/redis-6379.conf 
                        redis-server tlconfig/redis-6380.conf 
                        redis-server tlconfig/redis-6381.conf 

        1.5 Client connection

         Use three command line windows to connect redis service .

        1.6  Master slave replication mode

         Three common moves : 
                One master and two subordinates
                 It's passed down from generation to generation
                 Going to

2.1 What is sentinel mode

                 A group of sentinel Can monitor multiple master
                  The automatic version of anti guest oriented , It can be seen from the anti guest focus , When the main library goes down , You need to manually reselect the new master, And modify it again slave The main library of points to . Sentinel mode can monitor the main library in the background in case of failure , Then automatically select a new master database from the slave database according to the vote , And other slave libraries take the new master library as master.
The difference between it and anti guest oriented is that it is old master After reconnection , old master Will also become new master Of slave.
sentinel monitor Name of monitored database （ Customize ） Monitored database ip Address Port number of monitored database Number of votes , Indicates that when the monitored database fails , Automatically vote from the Library , When the slave database reaches the specified number of votes, it becomes the new master database of other slave databases .

2.2 Environment building

2.2.1  newly build sentinel.conf

         newly build sentinel.conf file , The name must not be wrong
        cd /usr/local/bin
        touch sentinel.conf

2.2.2 To configure sentinel.conf

        sentinel monitor 145-79 192.168.2.145 6379 1

        sentinel auth-pass 145-79 root

2.2.3 start-up

                 start-up 6379,6380,6381
                79 Respectively 80 and 81 Main library （ One master and two subordinates ）

                 The new window uses redis-sentinel sentinel.conf With sentinel Way to start redis Monitoring service

                 use shutdown demonstration 79 After downtime , It can be seen from the log that , The background is voting to select a new master library from the slave libraries .