哨兵(sentinel)模式
第一步：首先创建：touch sentinel.conf文件
第二步：编辑哨兵文件
vim sentinel.conf，内容如下：
# host6379是被监控主机名称(自己取名) IP 端口 1
sentinel monitor host6379 127.0.0.1 6379 1
注：上面的1，表示主机挂掉后slave投票，谁票多谁就成为主机。
第三步：启动哨兵
进入redis安装bin目录执行该命令：
redis-sentinel /usr/local/etc/sentinel.conf
结果如下：
7513:X 20 Sep 2021 09:45:13.410 # oO0OoOo Redis is starting oO0OoO0Oo
7513:X 20 Sep 2021 09:45:13.410 # Redis version=6.2.5, bits=64, commit=000000, modified=0, pid=7915, just started
7513:X 20 Sep 2021 09:45:13.410 # Configuration loaded
7513:X 20 Sep 2021 09:45:13.411 * Increased maximum number of open files to 10032 (it was originally set to 256).
7513:X 20 Sep 2021 09:45:13.411 * monotonic clock: POSIX clock_gettime_.__.-``__ ''-.__.-`` `. `_. ''-._ Redis 6.2.5 (00000000/0) 64 bit.-`` .-```. ```\/ _.,_ ''-._( ' , .-` | `, ) Running in sentinel mode|`-._`-...-` __...-.``-._|'` _.-'| Port: 26379| `-._ `._ / _.-' | PID: 7622`-._ `-._ `-./ _.-' _.-'|`-._`-._ `-.__.-' _.-'_.-'|| `-._`-._ _.-'_.-' | https://redis.io`-._ `-._`-.__.-'_.-' _.-'|`-._`-._ `-.__.-' _.-'_.-'|| `-._`-._ _.-'_.-' |`-._ `-._`-.__.-'_.-' _.-'`-._ `-.__.-' _.-'`-._ _.-'`-.__.-'7513:X 20 Sep 2021 09:45:13.413 # Sentinel ID is 2b8f846df1ec353hggjk25c34hg6212d4hgfghj82e7
# 监控6379主机
7513:X 20 Sep 2021 09:45:13.413 # +monitor master host6379 127.0.0.1 6379 quorum 1
# 巡逻6380 和 6381从机，一旦上面6379挂掉了，就投票选出新的master
7513:X 20 Sep 2021 09:45:13.420 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ host6379 127.0.0.1 6379
7513:X 20 Sep 2021 09:45:13.421 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ host6379 127.0.0.1 6379第五步：故意让6379挂掉，执行shutdown
哨兵缺点
由于所有的写操作先在master上操作，然后同步更新到slave上，所以从master同步到Slave有一定的延迟，当系统很繁忙时，延迟问题更加严重。
更多文章已被Github收录：https://github.com/niutongg/JavaLeague
