Redis learning notes (2) - power node of station B

008- redis The business of

8.1 Introduce

8.2 Common commands

（1）multi

（2）exec

（3）discard

（4）watch

（5）unwatch

8.3 Summary

009- redis Publish and subscribe messages （ understand ）

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010- redis Master-slave replication of

10.1 Introduce

 Main library master Write data   Slave Library slave Read the data 
 After the main database reads the data   Copy data to the slave Library 
 This can improve efficiency 

 After the host data is updated, according to the configuration and Policy , Automatic synchronization to slave master/slave Mechanism ,Master Write first ,Slave Mainly reading .

10.2 Build one master and two slaves

 Just watch the video here 

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17、redis Master-slave replication of ： From less to more 、 Write and read 、 Read / write separation 、 Master write synchronous replication to slave .
    Build one master and two slaves redis colony ：
   1)、 Build three redis service ： Use one redis Simulate three redis service 
        Provide three points redis The configuration file ：redis6379.conf、redis6380.conf、redis6381.conf
            Modify three configuration files : With redis6379.conf For example 
	         bind 127.0.0.1
	         port 6379
	         pidfile /var/run/redis_6379.pid
			 logfile "6379.log"
			 dbfilename dump6379.rdb
       Use three... Respectively redis The configuration file , Start the three redis service ：
           redis-server redis6379.conf &
		   redis-server redis6380.conf &
		   redis-server redis6381.conf &
   2) adopt redis The client is connected to three servers respectively redis service ：
        redis-cli -h 127.0.0.1 -p 6379
		redis-cli -h 127.0.0.1 -p 6380
		redis-cli -h 127.0.0.1 -p 6381
   3) Check three redis The master-slave role of services in the cluster ：
        info replication
	 By default , be-all redis Services are hosts , That is, you can write and read , But they haven't been from the machine yet .
   4) First in 6379 Write operation ：
        set k1 v1
      Three stations rdis Services are independent of each other , They don't influence each other .
   5) Set up master-slave relationship ： Set never set the master 
      stay 6380 On the implementation ：slaveof 127.0.0.1 6379
      stay 6381 On the implementation ：slaveof 127.0.0.1 6379
   6) Copy in full ： Once the master-slave relationship is determined , It will automatically copy the existing data on the master database to the slave database . 
      stay 6380 and 6381 On the implementation ：keys *
   7) Incremental replication ： The data written by the master database will be automatically synchronized to the slave database .
      stay 6379 On the implementation ：set k2 v2
      stay 6380 and 6381 On the implementation ：keys *
   8) Write and read , Read / write separation ： 
      stay 6380 and 6381 On the implementation ：set k3 v3  ===> Report errors 
   9) Host down 、 The slave stands by :
      close 6379 service ：redis-cli -h 127.0.0.1 -p 6379 shutdown

      see 6380 and 6381 The master-slave role of the service ：info replication
   10)、 Host recovery 、 Everything is back to normal ：
      restart 6379 service ：redis-server redis6379.conf &
      Client connection 6379：redis-cli -h 127.0.0.1 -p 6379
   11)、 From the machine down 、 The master is one less slave 、 Other slaves remain unchanged ：
      close 6380 service ： redis-cli -h 127.0.0.1 -p 6380 shutdown

      see 6379 The master-slave role of the service ：info replication
      see 6381 The master-slave role of the service ：info replication
   12)、 Recover from the machine 、 You need to reset the master-slave relationship ：
      restart 6380 service ：redis-server redis6380.conf &
      Client connection 6380：redis-cli -h 127.0.0.1 -p 6380

      stay 6380 On the implementation ： slaveof 127.0.0.1 6379
   13)、 Slave host ：
     a) Host down 、 The slave stands by ：
        close 6379 service ：redis-cli -h 127.0.0.1 -p 6379 shutdown
        see 6380 and 6381 The master-slave role of the service ：info replication
     b) The slave disconnects the original master-slave relationship ：
        stay 6380 On the implementation ：slaveof no one
        see 6380 The master-slave role of the service ：info replication
     c) Reset the master-slave relationship ：
        stay 6381 On the implementation ：slaveof 127.0.0.1 6380
     d) Previous host recovery 、 Become a loner ：
        restart 6379 service ：redis-server redis6379.conf &
        Client connection 6379：redis-cli -h 127.0.0.1 -p 6379
     e) Heaven becomes hell ：
        stay 6379 On the implementation ：slaveof 127.0.0.1 6381
        stay 6381 On the implementation ：info replication    It is both a master and a slave 
  
   Summary ： One host is configured with multiple slaves , One slave can be configured with multiple slaves , Thus forming a huge cluster architecture .
         Reduce the pressure of a host , But it increases the delay time between services .

10.3 The principle of replication

（1） Copy in full

（2） Incremental replication

10.4 Sentinel mode

18、redis Sentinel mode ： Host down 、 The automatic version of the slave computer .
    1) Build a one master and two slave cluster architecture ：(17 Five steps before the festival )
    2) Provide sentry profile ：
       stay redis Create a configuration file under installation ：redis_sentinel.conf
      sentinel monitor dc-redis 127.0.0.1 6379 1
    3) Start sentinel service ：
      redis-sentinel redis_sentinel.conf
    4) Host down ：
       close 6379 service ：redis-cli -h 127.0.0.1 -p 6379 shutdown
       The sentinel program automatically selects the slave computer .
    5) Previous host recovery ： Automatically subordinate to the new host .
       restart 6379 service ：redis-server redis6379.conf &
       Client connection 6379：redis-cli -h 127.0.0.1 -p 6379

10.5 Summary

011- Jedis operation Redis

19、java operation redis database ：
	jedis yes redis Officially provided operation redis Data technology .
     Put all the redis Instructions are defined as java Method of tool class , Method name and redis The instruction name of is exactly the same ;
     Development is accessed through programs redis, Just use the tool class and its methods .

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 stay java Program access redis：

1) establish maven Version of webapp engineering 

2) add to jedis rely on 
   <dependency>
     <groupId>redis.clients</groupId>
     <artifactId>jedis</artifactId>
     <version>3.1.0</version>
   </dependency>
 
3) establish Jedis Connect 
* close linux The firewall of 

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012- redis Client connection tool for

 It's like mysql equally   have access to navicat
redis There are similar navicat The same thing ：
	 But for redis, There is no difference between using and not using the visual interface