Redis sentry mode principle

Redis Sentry Mode Principle

Sentinel mode is a special mode. First of all, Redis provides the sentinel command. The sentinel is an independent As a process, it will run independently. The principle is that the sentinel monitors multiple running Redis instances by sending commands and waiting for the Redis server to respond.

Linux - redis sentinel cluster instance

Command arrangement

Official website address: http://redisdoc.com/

redis-cli info #查看redis数据库信息
redis-cli info replication #查看redis的复制授权信息
redis-cli info sentinel   #查看redis的哨兵信息

Configuration process

Ideas:

redis master-slave

一Master and two slaves plan

1. Environment preparation, prepare the redis architecture of one master and two slaves

redis-6379.conf

port 6379
daemonize yes
logfile "6379.log"
dbfilename "dump-6379.rdb"
dir "/opt/redis/6379/"
redis-6380.conf
port 6380
daemonize yes
logfile "6380.log"
dbfilename "dump-6380.rdb"
dir "/opt/redis/6380/"
slaveof  127.0.0.1  6379
redis-6381.conf
port 6381
daemonize yes
logfile "6381.log"
dbfilename "dump-6381.rdb"
dir "/opt/redis/6381/"
slaveof  127.0.0.1  6379

2. Prepare three data folders

mkdir -p  /opt/redis/{6379,6380,6381}

3. Start three databases respectively

[root@master sbredis]# redis-server redis-6379.conf 
[root@master sbredis]# redis-server redis-6380.conf 
[root@master sbredis]# redis-server redis-6381.conf

4. Detect the master-slave status

redis-cli -p 6379   info replication
redis-cli -p 6380   info replication
redis-cli -p 6381   info replication

5. Prepare three redis sentinels to detect the master-slave status

Prepare the configuration of the three sentinels File

redis-26379.conf

// Sentinel节点的端口
port 26379  
dir /var/redis/data/
logfile "26379.log"
// 当前Sentinel节点监控 192.168.119.10:6379 这个主节点
// 2代表判断主节点失败至少需要2个Sentinel节点节点同意
// mymaster是主节点的别名
sentinel monitor mymaster 192.168.119.10 6379 2
//每个Sentinel节点都要定期PING命令来判断Redis数据节点和其余Sentinel节点是否可达，如果超过30000毫秒30s且没有回复，则判定不可达
sentinel down-after-milliseconds mymaster 30000
//当Sentinel节点集合对主节点故障判定达成一致时，Sentinel领导者节点会做故障转移操作，选出新的主节点，
原来的从节点会向新的主节点发起复制操作，限制每次向新的主节点发起复制操作的从节点个数为1
sentinel parallel-syncs mymaster 1
//故障转移超时时间为180000毫秒
sentinel failover-timeout mymaster 180000
redis-26380.conf
port 7000
daemonize yes
dir "/opt/data"
logfile "7000.log"
dbfilename "dump-7000.rdb"
cluster-enabled yes   
cluster-config-file nodes-7000.conf
cluster-require-full-coverage no
redis-26381.conf

Three configuration files, only the port is different, quickly generate the configuration file through the command

[root@master sbredis]# sed "s/26379/26380/g"  redis-26379.conf   >  redis-26380.conf  
[root@master sbredis]# sed "s/26379/26381/g"  redis-26379.conf   >  redis-26381.conf

6. Start three sentinels respectively

[root@master sbredis]# redis-sentinel redis-26379.conf 
[root@master sbredis]# redis-sentinel redis-26380.conf 
[root@master sbredis]# redis-sentinel redis-26381.conf

7. Detect the sentinel, master-slave status

redis-cli -p 26379  info sentinel

When you see the following information, you are like me

[root@master sbredis]# redis-cli -p 26379  info  sentinel
Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=s17ms,status=ok,address=127.0.0.1:6379,slaves=2,sentinels=3

8. Test, kill the master redis, and see if it switches automatically

ps -ef|grep redis
    kill 进程
    ..

9. Start redis 6379 again to see if it has joined the master-slave cluster

redis-server redis-6379.conf

Recommended tutorial: "Redis Tutorial"

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