一.redis集群的概念
现用redis做缓存服务器，redis是一个单点，当一台机器岩机的时候，redis的服务完全停止，这时就会影响其他服务的正常运行，所以我们要做的是redis主从复制及主动切换。
首先介绍下怎么样做redis主备切换，需要用到redis的sentinel做一个主从切换的集群管理。redis主从服务（1个master，多个salve），然后通过redis官方的监控工具Sentinel（哨兵），对每个节点进行监控，实现自动故障迁移，即master死掉，将salve升级为master。基本原理是：心跳机制+投票裁决。
Redis 的 Sentinel 系统用于管理多个 Redis 服务器（instance）， 该系统执行以下三个任务：
监控（Monitoring）： Sentinel 会不断地检查你的主服务器和从服务器是否运作正常。
提醒（Notification）： 当被监控的某个 Redis 服务器出现问题时， Sentinel 可以通过API 向管理员或者其他应用程序发送通知。
自动故障迁移（Automatic failover）： 当一个主服务器不能正常工作时，Sentinel 会开始一次自动故障迁移操作， 它会将失效主服务器的其中一个从服务器升级为新的主服务器， 并让失效主服务器的其他从服务器改为复制新的主服务器；当客户端试图连接失效的主服务器时， 集群也会向客户端返回新主服务器的地址， 使得集群可以使用新主服务器代替失效服务器。
Redis Sentinel 是一个分布式系统， 你可以在一个架构中运行多个 Sentinel 进程（progress）， 这些进程使用流言协议（gossip protocols)来接收关于主服务器是否下线的信息， 并使用投票协议（agreementprotocols）来决定是否执行自动故障迁移，以及选择哪个从服务器作为新的主服务器。
虽然 Redis Sentinel 释出为一个单独的可执行文件 redis-sentinel， 但实际上它只是一个运行在特殊模式下的 Redis 服务器， 你可以在启动一个普通 Redis 服务器时通过给定 --sentinel 选项来启动Redis Sentinel 。
实验环境：er2:
主：server1：172.25.17.1
从：server2：172.25.17.2
实验部署：
配置主从复制：
主：
1.下载;
http://download.redis.io/releases/redis-5.0.3.tar.gz
2.编译安装:
[root@server1 ~]#tar zxf redis-5.0.3.tar.zxf
[root@server1 ~]# cd redis-5.0.3/
[root@server1 ~]# systemctl stop mysqld
[root@server1 ~]# systemctl disabled mysqld
Unknown operation 'disabled'.
[root@server1 ~]# systemctl disable mysqld
Removed symlink /etc/systemd/system/multi-user.target.wants/mysqld.service.
[root@server1 ~]# cd redis-5.0.3
[root@server1 redis-5.0.3]# make && make install
cd src && make all
make[1]: Entering directory `/root/redis-5.0.3/src'
Hint: It's a good idea to run 'make test' ;)
make[1]: Leaving directory `/root/redis-5.0.3/src'
cd src && make install
make[1]: Entering directory `/root/redis-5.0.3/src'
Hint: It's a good idea to run 'make test' ;)
INSTALL install
INSTALL install
INSTALL install
INSTALL install
INSTALL install
make[1]: Leaving directory `/root/redis-5.0.3/src'
[root@server1 redis-5.0.3]# cd utils/
[root@server1 utils]# ./install_server.sh #默认回车
Welcome to the redis service installer
This script will help you easily set up a running redis server
Please select the redis port for this instance: [6379]
Selecting default: 6379
Please select the redis config file name [/etc/redis/6379.conf]
Selected default - /etc/redis/6379.conf
Please select the redis log file name [/var/log/redis_6379.log]
Selected default - /var/log/redis_6379.log
Please select the data directory for this instance [/var/lib/redis/6379]
Selected default - /var/lib/redis/6379
Please select the redis executable path [/usr/local/bin/redis-server]
Selected config:
Port : 6379
Config file : /etc/redis/6379.conf
Log file : /var/log/redis_6379.log
Data dir : /var/lib/redis/6379
Executable : /usr/local/bin/redis-server
Cli Executable : /usr/local/bin/redis-cli
Is this ok? Then press ENTER to go on or Ctrl-C to abort.
Copied /tmp/6379.conf => /etc/init.d/redis_6379
Installing service...
Successfully added to chkconfig!
Successfully added to runlevels 345!
/var/run/redis_6379.pid exists, process is already running or crashed
Installation successful!
[root@server1 utils]# /etc/init.d/redis_6379 status
Redis is running (892)
[root@server1 utils]# /etc/init.d/redis_6379 restart
Stopping ...
Redis stopped
Starting Redis server...
[root@server1 utils]# vim /etc/redis/6379.conf #监听访问ip修改,设置为监听本机所有6379端口
70 bind 0.0.0.0
[root@server1 utils]# /etc/init.d/redis_6379 restart
Stopping ...
Redis stopped
Starting Redis server...
[root@server1 utils]# netstat -antlp #查看端口为6379
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:6379 0.0.0.0:* LISTEN 2489/redis-server 0
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1366/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 2020/master
tcp 0 0 127.0.0.1:6379 127.0.0.1:60340 TIME_WAIT -
tcp 0 0 172.25.17.1:22 172.25.17.250:36060 ESTABLISHED 2131/sshd: root@pts
tcp 0 0 172.25.17.1:6379 172.25.17.4:39042 ESTABLISHED 2489/redis-server 0
tcp6 0 0 :::22 :::* LISTEN 1366/sshd
tcp6 0 0 ::1:25 :::* LISTEN 2020/master 从：
1.下载;
http://download.redis.io/releases/redis-5.0.3.tar.gz
2.编译安装
[root@server2 ~]# tar zxf redis-5.0.3.tar.zxf
[root@server2 ~]# cd redis-5.0.3/
[root@server2 ~]# systemctl stop mysqld
[root@server2 ~]# systemctl disable mysqld
Removed symlink /etc/systemd/system/multi-user.target.wants/mysqld.service.
[root@server2 ~]# cd redis-5.0.3/
[root@server2 redis-5.0.3]# make && make install
cd src && make all
make[1]: Entering directory `/root/redis-5.0.3/src'
Hint: It's a good idea to run 'make test' ;)
make[1]: Leaving directory `/root/redis-5.0.3/src'
cd src && make install
make[1]: Entering directory `/root/redis-5.0.3/src'
Hint: It's a good idea to run 'make test' ;)
INSTALL install
INSTALL install
INSTALL install
INSTALL install
INSTALL install
make[1]: Leaving directory `/root/redis-5.0.3/src'
[root@server2 redis-5.0.3]# cd utils/
[root@server2 utils]# ./install_server.sh #默认回车
Welcome to the redis service installer
This script will help you easily set up a running redis server
Please select the redis port for this instance: [6379]
Selecting default: 6379
Please select the redis config file name [/etc/redis/6379.conf]
Selected default - /etc/redis/6379.conf
Please select the redis log file name [/var/log/redis_6379.log]
Selected default - /var/log/redis_6379.log
Please select the data directory for this instance [/var/lib/redis/6379]
Selected default - /var/lib/redis/6379
Please select the redis executable path [/usr/local/bin/redis-server]
Selected config:
Port : 6379
Config file : /etc/redis/6379.conf
Log file : /var/log/redis_6379.log
Data dir : /var/lib/redis/6379
Executable : /usr/local/bin/redis-server
Cli Executable : /usr/local/bin/redis-cli
Is this ok? Then press ENTER to go on or Ctrl-C to abort.
Copied /tmp/6379.conf => /etc/init.d/redis_6379
Installing service...
Successfully added to chkconfig!
Successfully added to runlevels 345!
/var/run/redis_6379.pid exists, process is already running or crashed
Installation successful!
[root@server2 utils]# /etc/init.d/redis_6379 status
Redis is running (1363)
[root@server2 utils]# /etc/init.d/redis_6379 restart
Stopping ...
Redis stopped
Starting Redis server...
[root@server2 utils]# vim /etc/redis/6379.conf #监听访问ip修改
70 bind 0.0.0.0
[root@server2 utils]# vim /etc/redis/6379.conf
文章末尾加入如下，指定连接那个库，这里设置为server1的ip以及接口：
slaveof 172.25.17.1 6379
[root@server2 utils]# /etc/init.d/redis_6379 restart
Stopping ...
Redis stopped
Starting Redis server...
[root@server2 utils]# netstat -antlp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:6379 0.0.0.0:* LISTEN 2382/redis-server 0
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1855/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 2024/master
tcp 0 0 172.25.17.2:22 172.25.17.250:52914 ESTABLISHED 2135/sshd: root@pts
tcp 0 0 127.0.0.1:6379 127.0.0.1:41282 TIME_WAIT -
tcp6 0 0 :::22 :::* LISTEN 1855/sshd
tcp6 0 0 ::1:25 :::* LISTEN 2024/master
测试：
在server1上建立一条key-valye数据，server2上可以看到同步成功
[root@server1 utils]# redis-cli
127.0.0.1:6379> set xys 234
OK
[root@server2 utils]# redis-cli
127.0.0.1:6379> get xys
"234"
主从切换：
主从配置一致：
root@server1 ~]# cd redis-5.0.3
[root@server1 redis-5.0.3]# cp sentinel.conf /etc/redis/
[root@server1 redis-5.0.3]# vim /etc/redis/sentinel.conf
17 protected-mode no
18
84 sentinel monitor mymaster 172.25.17.1 6379 2
146 sentinel parallel-syncs mymaster 10000
121sentinel parallel-sync mymaster 1
启动
[root@server1 redis-5.0.3]# redis-server /etc/redis/sentinel.conf --sentinel
从机：server4:172.25.17.4
编译安装redis
[root@server1 redis-5.0.3]# yum install rsync -y
[root@server1 ~]# rsync -a redis-5.0.3 server4:
server4;
[root@server4 ~]# yum install rsync -y
[root@server4 ~]# cd redis-5.0.3/
[root@server4 redis-5.0.3]# make install
cd src && make install
make[1]: Entering directory `/root/redis-5.0.3/src'
Hint: It's a good idea to run 'make test' ;)
INSTALL install
INSTALL install
INSTALL install
INSTALL install
INSTALL install
make[1]: Leaving directory `/root/redis-5.0.3/src'
[root@server4 redis-5.0.3]# cd utils/
[root@server4 utils]# ./install_server.sh
Welcome to the redis service installer
This script will help you easily set up a running redis server
Please select the redis port for this instance: [6379]
Selecting default: 6379
Please select the redis config file name [/etc/redis/6379.conf]
Selected default - /etc/redis/6379.conf
Please select the redis log file name [/var/log/redis_6379.log]
Selected default - /var/log/redis_6379.log
Please select the data directory for this instance [/var/lib/redis/6379]
Selected default - /var/lib/redis/6379
Please select the redis executable path [/usr/local/bin/redis-server]
Selected config:
Port : 6379
Config file : /etc/redis/6379.conf
Log file : /var/log/redis_6379.log
Data dir : /var/lib/redis/6379
Executable : /usr/local/bin/redis-server
Cli Executable : /usr/local/bin/redis-cli
Is this ok? Then press ENTER to go on or Ctrl-C to abort.
Copied /tmp/6379.conf => /etc/init.d/redis_6379
Installing service...
Successfully added to chkconfig!
Successfully added to runlevels 345!
/var/run/redis_6379.pid exists, process is already running or crashed
Installation successful!
[root@server4 utils]# vim /etc/redis/6379.conf
[root@server4 utils]# /etc/init.d/redis_6379 restart
Stopping ...
Redis stopped
Starting Redis server...
[root@server4 utils]# cd
[root@server4 ~]# vim /etc/redis/6379.conf
[root@server4 ~]# /etc/init.d/redis_6379 restart
Stopping ...
Redis stopped
Starting Redis server...
[root@server4 ~]# redis-cli
127.0.0.1:6379> get name
(nil)
127.0.0.1:6379> get xys
"234"
127.0.0.1:6379> exit
server1:
[root@server1 redis]# scp sentinel.conf server2:/etc/redis/
sentinel.conf 100% 9711 9.5KB/s 00:00
[root@server1 redis]# scp sentinel.conf server4:/etc/redis/
sentinel.conf 100% 9711 9.5KB/s 00:00
[root@server1 redis]# redis-server /etc/redis/sentinel.conf --sentinel
2547:X 28 Feb 2019 11:34:27.248 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
2547:X 28 Feb 2019 11:34:27.248 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=2547, just started
2547:X 28 Feb 2019 11:34:27.248 # Configuration loaded
2547:X 28 Feb 2019 11:34:27.249 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 5.0.3 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 2547
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
2547:X 28 Feb 2019 11:34:27.249 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
2547:X 28 Feb 2019 11:34:27.311 # Sentinel ID is 7edf3c86b786f815d70ba471ab4b71f99d018dd4
2547:X 28 Feb 2019 11:34:27.311 # +monitor master mymaster 172.25.17.1 6379 quorum 2
2547:X 28 Feb 2019 11:34:27.312 * +slave slave 172.25.17.2:6379 172.25.17.2 6379 @ mymaster 172.25.17.1 6379
2547:X 28 Feb 2019 11:34:27.332 * +slave slave 172.25.17.4:6379 172.25.17.4 6379 @ mymaster 172.25.17.1 6379
2547:X 28 Feb 2019 11:35:11.441 * +sentinel sentinel 362b5bef2fcee02ae39b28e873828334a10c9346 172.25.17.2 26379 @ mymaster 172.25.17.1 6379
2547:X 28 Feb 2019 11:35:17.358 * +sentinel sentinel 8ec059feb2d8c2feec053ff3d81da2f1a4eef9e2 172.25.17.4 26379 @ mymaster 172.25.17.1 6379
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
[root@server2 utils]# redis-server /etc/redis/sentinel.conf --sentinel
2431:X 28 Feb 2019 11:35:10.269 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
2431:X 28 Feb 2019 11:35:10.269 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=2431, just started
2431:X 28 Feb 2019 11:35:10.269 # Configuration loaded
2431:X 28 Feb 2019 11:35:10.270 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 5.0.3 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 2431
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
2431:X 28 Feb 2019 11:35:10.271 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
2431:X 28 Feb 2019 11:35:10.310 # Sentinel ID is 362b5bef2fcee02ae39b28e873828334a10c9346
2431:X 28 Feb 2019 11:35:10.310 # +monitor master mymaster 172.25.17.1 6379 quorum 2
2431:X 28 Feb 2019 11:35:10.312 * +slave slave 172.25.17.2:6379 172.25.17.2 6379 @ mymaster 172.25.17.1 6379
2431:X 28 Feb 2019 11:35:10.332 * +slave slave 172.25.17.4:6379 172.25.17.4 6379 @ mymaster 172.25.17.1 6379
2431:X 28 Feb 2019 11:35:10.764 * +sentinel sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
2431:X 28 Feb 2019 11:35:18.235 * +sentinel sentinel 8ec059feb2d8c2feec053ff3d81da2f1a4eef9e2 172.25.17.4 26379 @ mymaster 172.25.17.1 6379
2431:X 28 Feb 2019 11:37:11.761 # +sdown sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
2431:X 28 Feb 2019 11:40:40.595 # -sdown sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
2431:X 28 Feb 2019 11:41:22.492 # +sdown sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@2
sercer4:
[root@server4 ~]# redis-server /etc/redis/sentinel.conf --sentinel
2428:X 28 Feb 2019 11:35:15.831 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
2428:X 28 Feb 2019 11:35:15.831 # Redis version=5.0.3, bits=64, commit=00000000, modified=0, pid=2428, just started
2428:X 28 Feb 2019 11:35:15.831 # Configuration loaded
2428:X 28 Feb 2019 11:35:15.831 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 5.0.3 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in sentinel mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379
| `-._ `._ / _.-' | PID: 2428
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
2428:X 28 Feb 2019 11:35:15.832 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
2428:X 28 Feb 2019 11:35:15.967 # Sentinel ID is 8ec059feb2d8c2feec053ff3d81da2f1a4eef9e2
2428:X 28 Feb 2019 11:35:15.968 # +monitor master mymaster 172.25.17.1 6379 quorum 2
2428:X 28 Feb 2019 11:35:15.969 * +slave slave 172.25.17.2:6379 172.25.17.2 6379 @ mymaster 172.25.17.1 6379
2428:X 28 Feb 2019 11:35:16.023 * +slave slave 172.25.17.4:6379 172.25.17.4 6379 @ mymaster 172.25.17.1 6379
2428:X 28 Feb 2019 11:35:16.082 * +sentinel sentinel 362b5bef2fcee02ae39b28e873828334a10c9346 172.25.17.2 26379 @ mymaster 172.25.17.1 6379
2428:X 28 Feb 2019 11:35:16.566 * +sentinel sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
2428:X 28 Feb 2019 11:37:11.465 # +sdown sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
2428:X 28 Feb 2019 11:40:40.426 # -sdown sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
2428:X 28 Feb 2019 11:41:22.270 # +sdown sentinel 7edf3c86b786f815d70ba471ab4b71f99d018dd4 172.25.17.1 26379 @ mymaster 172.25.17.1 6379
由监控信息可见，此时master为172.25.17.1 两个slave为172.25.17.2和172.25.17.4由监控信息可见，此时master为172.25.17.1 两个slave为172.25.17.2和172.25.17.4
sever1查询信息：
[root@server1 ~]# redis-cli -p 26379
127.0.0.1:26379> info
master0:name=mymaster,status=ok,address=172.25.17.1:6379,slaves=2,sentinels=3
此时挂掉server1:
redis-cli -p 6379
SHUTDOWNserver2和server4显示master已经交换到server2 此时的两个slave为172.25.17.1和172.25.17.4
sever2:
2431:X 28 Feb 2019 11:42:49.340 # +switch-master mymaster 172.25.17.1 6379 172.25.17.2 6379
2431:X 28 Feb 2019 11:42:49.340 * +slave slave 172.25.17.4:6379 172.25.17.4 6379 @ mymaster 172.25.17.2 6379
2431:X 28 Feb 2019 11:42:49.340 * +slave slave 172.25.17.1:6379 172.25.17.1 6379 @ mymaster 172.25.17.2 6379
2431:X 28 Feb 2019 11:45:50.230 * +fix-slave-config slave 172.25.17.1:6379 172.25.17.1 6379 @ mymaster 172.25.17.2 6379
server4:
2428:X 28 Feb 2019 11:42:50.057 # +switch-master mymaster 172.25.17.1 6379 172.25.17.2 6379
2428:X 28 Feb 2019 11:42:50.058 * +slave slave 172.25.17.4:6379 172.25.17.4 6379 @ mymaster 172.25.17.2 6379
2428:X 28 Feb 2019 11:42:50.058 * +slave slave 172.25.17.1:6379 172.25.17.1 6379 @ mymaster 172.25.17.2 6379
重新启动server1:
cd /etc/redis/
vim 6379.conf
写入：
slaveof 172.25.17.2 6379
/ect/init.d/redis_6379 status
/ect/init.d/redis_6379 start