Redis以主从的模式搭建集群后，如果主节点Master挂掉，虽然可以实现将备用节点Slave切换成主节点，但是Redis本身并没有自动监控机制，需要借助Sentinel哨兵模式，实现监控并实现自动切换。为了实现Sentinel的高可用，需要sentinel也以集群模式来搭建，这里通过一台机器的不同端口来模拟。相关环境信息如下：
1、Redis集群信息：
| 角色 | IP地址 | 监听端口 |
| Master | 127.0.0.1 | 6379 |
| Slave | 127.0.0.1 | 6380 |
| Slave | 127.0.0.1 | 6381 |
Sentinel集群信息：
| 哨兵角色 | IP地址 | 监听端口 |
| Node-1 | 127.0.0.1 | 26379 |
| Node-2 | 127.0.0.1 | 26380 |
| Node-3 | 127.0.0.1 | 26381 |
2、Redis集群搭建过程参考上篇，这里不再描述。首先启动Redis的主节点和两个Slave节点。
进入Master节点，查看信息：
1 [root@VM_0_14_centos bin]# ./redis-cli -h 127.0.0.1 -p 6379 -a funnyboy 2 Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe. 3 127.0.0.1:6379> info replication 4 # Replication 5 role:master 6 connected_slaves:2 7 slave0:ip=127.0.0.1,port=6380,state=online,offset=4256,lag=0 8 slave1:ip=127.0.0.1,port=6381,state=online,offset=4256,lag=1 9 master_replid:d5802af0905736ae28201050ce4871ee2921c16c10 master_replid2:000000000000000000000000000000000000000011 master_repl_offset:425612 second_repl_offset:-113 repl_backlog_active:114 repl_backlog_size:104857615 repl_backlog_first_byte_offset:116 repl_backlog_histlen:425617 127.0.0.1:6379>
显示当前节点role为master，并且连接的slave个数为2，OK。
分别进入两个slave节点查看信息：
1 [root@VM_0_14_centos bin]# ./redis-cli -h 127.0.0.1 -p 6380 -a funnyboy 2 Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe. 3 127.0.0.1:6380> info replication 4 # Replication 5 role:slave 6 master_host:127.0.0.1 7 master_port:6379 8 master_link_status:up 9 master_last_io_seconds_ago:810 master_sync_in_progress:011 slave_repl_offset:442412 slave_priority:10013 slave_read_only:114 connected_slaves:015 master_replid:d5802af0905736ae28201050ce4871ee2921c16c16 master_replid2:000000000000000000000000000000000000000017 master_repl_offset:442418 second_repl_offset:-119 repl_backlog_active:120 repl_backlog_size:104857621 repl_backlog_first_byte_offset:122 repl_backlog_histlen:442423 127.0.0.1:6380>
1 [root@VM_0_14_centos bin]# ./redis-cli -h 127.0.0.1 -p 6381 -a funnyboy 2 Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe. 3 127.0.0.1:6381> info replication 4 # Replication 5 role:slave 6 master_host:127.0.0.1 7 master_port:6379 8 master_link_status:up 9 master_last_io_seconds_ago:510 master_sync_in_progress:011 slave_repl_offset:455012 slave_priority:10013 slave_read_only:114 connected_slaves:015 master_replid:d5802af0905736ae28201050ce4871ee2921c16c16 master_replid2:000000000000000000000000000000000000000017 master_repl_offset:455018 second_repl_offset:-119 repl_backlog_active:120 repl_backlog_size:104857621 repl_backlog_first_byte_offset:122 repl_backlog_histlen:455023 127.0.0.1:6381>
角色都为slave，并且master信息正常。确保Redis集群OK后，开始准备搭建sentinel集群。
3、Sentinel集群搭建
step1、将redis-sentinel拷贝到redis对应的执行目录bin(该命令是redis-server的一个连接，用redis-server也OK，后面讲到，启动sentinel会有两种方式)，然后拷贝sentinel.config到redis配置文件目录config。
step2、分别编辑sentinel的配置文件(没特别强调的保持默认即可)
sentinel-26379.conf配置如下：
1 daemonize yes #开启后台守护进程2 port 26379 #端口配置3 pidfile "/usr/local/redis/pid/redis-sentinel-26379.pid" #PID文件4 logfile "/usr/local/redis/logs/sentinel-26379.log" #日志文件5 sentinel monitor mymaster 127.0.0.1 6379 2 #哨兵监控配置。注意，如果配置了认证，改配置必须在auth-pass配置之前，否则启动报找不到master的错误6 sentinel auth-pass mymaster funnyboy #认证配置7 sentinel down-after-milliseconds mymaster 5000 #master或者slave多少时间（默认30秒）不能使用标记为down状态。8 sentinel failover-timeout mymaster 9000 #若哨兵在配置值内未能完成故障转移操作，则任务本次故障转移失败。
sentinel-26380.conf配置如下：
1 daemonize yes #开启后台守护进程2 port 26380 #端口配置3 pidfile "/usr/local/redis/pid/redis-sentinel-26380.pid" #PID文件4 logfile "/usr/local/redis/logs/sentinel-26380.log" #日志文件5 sentinel monitor mymaster 127.0.0.1 6379 2 #哨兵监控配置。注意，如果配置了认证，改配置必须在auth-pass配置之前，否则启动报找不到master的错误6 sentinel auth-pass mymaster funnyboy #认证配置7 sentinel down-after-milliseconds mymaster 5000 #master或者slave多少时间（默认30秒）不能使用标记为down状态。8 sentinel failover-timeout mymaster 9000 #若哨兵在配置值内未能完成故障转移操作，则任务本次故障转移失败。
sentinel-26381.conf配置如下：
1 daemonize yes #开启后台守护进程2 port 26381 #端口配置3 pidfile "/usr/local/redis/pid/redis-sentinel-26381.pid" #PID文件4 logfile "/usr/local/redis/logs/sentinel-26381.log" #日志文件5 sentinel monitor mymaster 127.0.0.1 6379 2 #哨兵监控配置。注意，如果配置了认证，改配置必须在auth-pass配置之前，否则启动报找不到master的错误6 sentinel auth-pass mymaster funnyboy #认证配置7 sentinel down-after-milliseconds mymaster 5000 #master或者slave多少时间（默认30秒）不能使用标记为down状态。8 sentinel failover-timeout mymaster 9000 #若哨兵在配置值内未能完成故障转移操作，则任务本次故障转移失败。
step3、启动哨兵监控程序：
1 2 [root@VM_0_14_centos redis]# ./bin/redis-sentinel ./config/sentinel-26379.conf 3 [root@VM_0_14_centos redis]# ./bin/redis-sentinel ./config/sentinel-26380.conf 4 [root@VM_0_14_centos redis]# ./bin/redis-sentinel ./config/sentinel-26381.conf
启动有两种方式：
一是执行：redis-sentinel sentinel.conf
二是执行：redis-server sentinel --sentinel
step4、通过哨兵连接，并检查信息：
1 [root@VM_0_14_centos bin]# ./redis-cli -h 127.0.0.1 -p 26379 -a funnyboy 2 Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe. 3 127.0.0.1:26379> info sentinel 4 # Sentinel 5 sentinel_masters:1 6 sentinel_tilt:0 7 sentinel_running_scripts:0 8 sentinel_scripts_queue_length:0 9 sentinel_simulate_failure_flags:010 master0:name=mymaster,status=ok,address=127.0.0.1:6379,slaves=2,sentinels=311 127.0.0.1:26379>
可以看到监控的redis服务，一个Master、两个Slave、sentinels = 3 说明配置OK。
4、模拟场景：Redis Master节点挂掉，查看Redis集群状态。
step1、关掉Master节点：
1 [root@VM_0_14_centos bin]# ./redis-cli -p 6379 -a funnyboy2 Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.3 127.0.0.1:6379> shutdown4 not connected> 5 [root@VM_0_14_centos bin]#
step2、通过哨兵查看集群状态：
1 127.0.0.1:26379> info sentinel2 # Sentinel3 sentinel_masters:14 sentinel_tilt:05 sentinel_running_scripts:06 sentinel_scripts_queue_length:07 sentinel_simulate_failure_flags:08 master0:name=mymaster,status=ok,address=127.0.0.1:6380,slaves=2,sentinels=39 127.0.0.1:26379>
通过sentinel信息可以看到，Master节点已经自动切换到6380端口了，说明主节点挂掉后，6380 Slave节点自动升级成为了Master节点。
step3、启动6379 redis服务，然后查看节点角色，此时6379变成了Slave，6380为Master节点，OK。
1 [root@VM_0_14_centos redis]# ./bin/redis-server ./config/redis-6379.conf 2 [root@VM_0_14_centos redis]# ./bin/redis-cli -p 6379 -a funnyboy 3 Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe. 4 127.0.0.1:6379> 5 127.0.0.1:6379> info replication 6 # Replication 7 role:slave 8 master_host:127.0.0.1 9 master_port:638010 master_link_status:up11 master_last_io_seconds_ago:112 master_sync_in_progress:013 slave_repl_offset:39267114 slave_priority:10015 slave_read_only:116 connected_slaves:017 master_replid:c77763408266bcebf233bdc9e59e3bcf14dc7a0818 master_replid2:000000000000000000000000000000000000000019 master_repl_offset:39267120 second_repl_offset:-121 repl_backlog_active:122 repl_backlog_size:104857623 repl_backlog_first_byte_offset:37858624 repl_backlog_histlen:14086