前言
前面已经部署了：redis的4对主从集群 + 1对主从session主从备份。如果redis集群中有宕机情况发生，怎么保障服务的可用性呢，本文准备在session服务器上添加启动哨兵服务，测试集群的容灾情况。
1.添加哨兵
a.重新整理集群
由于集群的连接操作均使用内网，实际应用同样。修改容器启动命令、配置文件，取消redis集群对外公网的端口映射、cli连接密码。另外节点太多不方便管理，所以减小点。
调整为无密码的3对主从集群，删除clm4、cls4：
/ # redis-cli --cluster del-node 172.1.30.21:6379 c2b42a6c35ab6afb1f360280f9545b3d1761725e>>> Removing node c2b42a6c35ab6afb1f360280f9545b3d1761725e from cluster 172.1.30.21:6379>>> Sending CLUSTER FORGET messages to the cluster...>>> SHUTDOWN the node./ # redis-cli --cluster del-node 172.1.50.21:6379 6d1b7a14a6d0be55a5fcb9266358bd1a42244d47>>> Removing node 6d1b7a14a6d0be55a5fcb9266358bd1a42244d47 from cluster 172.1.50.21:6379[ERR] Node 172.1.50.21:6379 is not empty! Reshard data away and try again.#需要先清空槽数据（rebalance成weigth=0）/ # redis-cli --cluster rebalance 172.1.50.21:6379 --cluster-weight 6d1b7a14a6d0be55a5fcb9266358bd1a42244d47=0Moving 2186 slots from 172.1.50.21:6379 to 172.1.30.11:6379###Moving 2185 slots from 172.1.50.21:6379 to 172.1.50.11:6379###Moving 2185 slots from 172.1.50.21:6379 to 172.1.50.12:6379###/ # redis-cli --cluster del-node 172.1.50.21:6379 6d1b7a14a6d0be55a5fcb9266358bd1a42244d47>>> Removing node 6d1b7a14a6d0be55a5fcb9266358bd1a42244d47 from cluster 172.1.50.21:6379>>> Sending CLUSTER FORGET messages to the cluster...>>> SHUTDOWN the node.缩容成功。
b.启动哨兵
这里修改rm/rs的容器启动命令：
docker run --name rm \ --restart=always \ --network=mybridge --ip=172.1.13.11 \ -v /root/tmp/dk/redis/data:/data \ -v /root/tmp/dk/redis/redis.conf:/etc/redis/redis.conf \ -v /root/tmp/dk/redis/sentinel.conf:/etc/redis/sentinel.conf \ -d cffycls/redis5:1.7 docker run --name rs \ --restart=always \ --network=mybridge --ip=172.1.13.12 \ -v /root/tmp/dk/redis_slave/data:/data \ -v /root/tmp/dk/redis_slave/redis.conf:/etc/redis/redis.conf \ -v /root/tmp/dk/redis_slave/sentinel.conf:/etc/redis/sentinel.conf \ -d cffycls/redis5:1.7参考《redis集群实现(六) 容灾与宕机恢复》、《Redis及其Sentinel配置项详细说明》，修改配置文件：
#若产生数据的存放路径dir /data/sentinel#<master-name> <ip> <redis-port> <quorum>#监视名，ip，port，保证一致性的最小数目sentinel monitor mymaster1 172.1.50.11 6379 2sentinel monitor mymaster2 172.1.50.12 6379 2sentinel monitor mymaster3 172.1.50.13 6379 2#sentinel down-after-milliseconds <master-name> <milliseconds>#监视名，认为此节点下线了的超时时间# Default is 30 seconds.sentinel down-after-milliseconds mymaster1 30000sentinel down-after-milliseconds mymaster2 30000sentinel down-after-milliseconds mymaster3 30000#sentinel parallel-syncs <master-name> <numslaves>#监视名，值设为 1 来保证每次只有一个slave 处于不能处理命令请求的状态sentinel parallel-syncs mymaster1 1sentinel parallel-syncs mymaster2 1sentinel parallel-syncs mymaster3 1#默认值# Default is 3 minutes.sentinel failover-timeout mymaster1 180000sentinel failover-timeout mymaster2 180000sentinel failover-timeout mymaster3 180000创建相应文件夹(xx/data/sentinel)，重启2个容器，并进入rm：
/ # redis-sentinel /etc/redis/sentinel.conf... ... 14:X 11 Jul 2019 18:25:24.418 # +monitor master mymaster3 172.1.50.13 6379 quorum 214:X 11 Jul 2019 18:25:24.419 # +monitor master mymaster1 172.1.50.11 6379 quorum 214:X 11 Jul 2019 18:25:24.419 # +monitor master mymaster2 172.1.50.12 6379 quorum 214:X 11 Jul 2019 18:25:24.421 * +slave slave 172.1.30.12:6379 172.1.30.12 6379 @ mymaster1 172.1.50.11 637914:X 11 Jul 2019 18:25:24.425 * +slave slave 172.1.30.13:6379 172.1.30.13 6379 @ mymaster2 172.1.50.12 637914:X 11 Jul 2019 18:26:14.464 # +sdown master mymaster3 172.1.50.13 6379 “不需要监视slave，监视了master的话，slave会自动加入到sentinel里边”，