Redis哨兵集群原理

单节点Redis的并发能力是有上限的，要进一步提高Redis的并发能力，就需要搭建主从集群，实现读写分离

• 主节点: 可以对Redis实现读写操作
• 从节点: 只可以对Redis实现读操作

但是，当master节点宕机后，我们就不能写数据到Redis,所以需要搭建一个三节点形成的Sentinel集群，来监管之前的Redis主从集群

1.Redis哨兵

Redis提供了哨兵（Sentinel）机制来实现主从集群的自动故障恢复。

哨兵的结构如图：

共包含6个节点，一个主两个从和三个哨兵。这里我们会在同一台虚拟机中开启6个redis实例，模拟主从集群，信息如下：

哨兵的作用如下：

• 监控：Sentinel 会不断检查您的master和slave是否按预期工作
• 自动故障恢复：如果master故障Sentinel会将一个slave提升为master。当故障实例恢复后也以新的master为主
• 通知：Sentinel充当Redis客户端的服务发现来源，当集群发生故障转移时会将最新信息推送给Redis的客户端

2. 准备实例和配置

要在同一台虚拟机开启6个实例，必须准备6份不同的配置文件和目录，配置文件所在目录也就是工作目录。 确保下面的配置已经更改（位置也别错）

# master
mkdir -p /redis-master-slave-sentinel/redis/master/config /redis-master-slave-sentinel/redis/master/data
cd /redis-master-slave-sentinel/redis/master/config
curl -O -L http://download.redis.io/releases/redis-6.0.20.tar.gz
tar -zxvf redis-6.0.20.tar.gz
cp /redis-master-slave-sentinel/redis/master/config/redis-6.0.20/redis.conf  /redis-master-slave-sentinel/redis/master/config/redis.conf
sed -i 's/bind 127.0.0.1/bind 0.0.0.0/' /redis-master-slave-sentinel/redis/master/config/redis.conf

# slave-1
mkdir -p /redis-master-slave-sentinel/redis/slave-1/config /redis-master-slave-sentinel/redis/slave-1/data
cd /redis-master-slave-sentinel/redis/slave-1/config/
cp /redis-master-slave-sentinel/redis/master/config/redis-6.0.20/redis.conf   /redis-master-slave-sentinel/redis/slave-1/config/redis.conf
sed -i 's/bind 127.0.0.1/bind 0.0.0.0/' /redis-master-slave-sentinel/redis/slave-1/config/redis.conf 

# slave-2
mkdir -p /redis-master-slave-sentinel/redis/slave-2/config /redis-master-slave-sentinel/redis/slave-2/data
cd /redis-master-slave-sentinel/redis/slave-2/config/
cp /redis-master-slave-sentinel/redis/master/config/redis-6.0.20/redis.conf   /redis-master-slave-sentinel/redis/slave-2/config/redis.conf
sed -i 's/bind 127.0.0.1/bind 0.0.0.0/' /redis-master-slave-sentinel/redis/slave-2/config/redis.conf


#redis-sentinel-1
mkdir -p /redis-master-slave-sentinel/sentinel/redis-sentinel-1  /redis-master-slave-sentinel/sentinel/redis-sentinel-1/s1
cd  /redis-master-slave-sentinel/sentinel/redis-sentinel-1


cat >> /redis-master-slave-sentinel/sentinel/redis-sentinel-1/sentinel.conf <<EOF
# 配置可参考 http://download.redis.io/redis-stable/sentinel.conf
# 配置说明 https://redis.io/topics/sentinel
port 26379
dir /tmp
sentinel monitor mymaster 192.168.150.102 6380 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel auth-pass mymaster 123456
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes
EOF



#redis-sentinel-2
mkdir -p /redis-master-slave-sentinel/sentinel/redis-sentinel-2  /redis-master-slave-sentinel/sentinel/redis-sentinel-2/s2
cd  /redis-master-slave-sentinel/sentinel/redis-sentinel-2


cat >> /redis-master-slave-sentinel/sentinel/redis-sentinel-2/sentinel.conf <<EOF
# 配置可参考 http://download.redis.io/redis-stable/sentinel.conf
# 配置说明 https://redis.io/topics/sentinel
port 26379
dir /tmp
sentinel monitor mymaster 192.168.150.102 6380 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel auth-pass mymaster 123456
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes
EOF


#redis-sentinel-3
mkdir -p /redis-master-slave-sentinel/sentinel/redis-sentinel-3  /redis-master-slave-sentinel/sentinel/redis-sentinel-3/s3
cd  /redis-master-slave-sentinel/sentinel/redis-sentinel-3


cat >> /redis-master-slave-sentinel/sentinel/redis-sentinel-3/sentinel.conf <<EOF
# 配置可参考 http://download.redis.io/redis-stable/sentinel.conf
# 配置说明 https://redis.io/topics/sentinel
port 26379
dir /tmp
sentinel monitor mymaster 192.168.150.102 6380 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel auth-pass mymaster 123456
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes
EOF

sentinel.conf说明

port 26379
dir /tmp
sentinel monitor mymaster 192.168.150.102 6380 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel auth-pass mymaster 123456
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes

sentinel.conf解读

• port 26379：是当前sentinel实例的端口
• sentinel monitor mymaster 192.168.150.102 6380 2：指定主节点信息 ○ mymaster：主节点名称，自定义，任意写 ○ 192.168.150.102 6380：主节点的ip和端口 ○ 2：选举master时的quorum值
• sentinel auth-pass mymaster 123456 :访问主节点时的密码