One 、 Master slave replication configuration

Case study ： One master and three followers

        Lord ：6378

         from ：6376、6377

# Here is what I use docker Create a container to show you , It can be understood as a virtual machine , If you still don't understand, you can ignore it .

docker run  --net host --name=myredis01 --privileged=true \
-v /data/docker/redis/redis.conf:/etc/redis/redis.conf \
-v /data/docker/redis/data:/data \
-d redis:6.2.6 \
redis-server /etc/redis/redis.conf --port 6378

docker run  --net host --name=myredis02 --privileged=true \
-v /data/docker/redis/redis.conf:/etc/redis/redis.conf \
-d redis:6.2.6 \
redis-server /etc/redis/redis.conf --port 6377

docker run  --net host --name=myredis03 --privileged=true \
-v /data/docker/redis/redis.conf:/etc/redis/redis.conf \
-d redis:6.2.6 \
redis-server /etc/redis/redis.conf --port 6376

1、 Get ready 3 platform redis Service startup

         And connect , This is not a demonstration , It's easy .

2、 Enter one of them to check the server status

        info replication

  It can be seen that they are all main servers , Then configure the master-slave relationship

3、 Configure master and slave

Get into 6377 and 6376 Slave execution

slaveof master server ip  port

4、 Several important points

1） When one of the slaves hangs up , Restart , It's not slave , Need to reconfigure , After reconfiguration , From the opportunity to immediately own all the hosts key

2） At this time, the host down After dropping , The slave will not be upgraded to the master server . After restarting the primary server , Primary server or primary server , This is different from the slave server

5、 Synchronization principle

1） After connecting to the master server , Send data synchronization message from the server to the main service

2） The master server receives a synchronization message from the slave server , Persistence of master server data ,rdb file , hold rdb The file is sent from the server , Get it from the server rdb To read --- Full amount of synchronization

3） Every time the master server writes , And data synchronization from the server --- The incremental synchronization

6、 Going to --- Sentinel mode

When sentinel mode is on , The Sentry will monitor whether the main service is down , If you hang up , From slave Choose a new one master.

stay redis Create a new file in a location of any server vim sentinel.conf, Write the following

sentinel monitor redismaster 47.95.33.138 6378 1

perform redis-sentinel /data/sentinel.conf Activate the sentry , If at this time 6378down It fell off , The remaining two of them will become master Keep working , If 6378 Restart again , Then he will become slave, Loss of eldest brother's power .

 1） shortcoming ： Replication delay

Because all the writing operations are first in Master On the operation , Then sync update to slave On , So from Master Synchronize to slave The machine has a certain delay , When the system is busy , The delay problem will be more serious ,slave The increase in the number of machines will make the problem more serious .

2） Select new master principle

        a. redis.conf In the configuration of the  replica-priority The smaller, the easier it is to be elected . Default 100

                replica-priority 100

        b. Select servers with high data offset , Generally speaking, it is , With the highest amount of synchronization with the previous master server

        c. choice runid The smallest slave

Two 、PHP、Java Link master-slave Services

according to sentinel Get the master server link from the master server name in the configuration , You can search for details by yourself