【Redis】的哨兵(sentinel)详解

2018-02-05 10:28:48来源:网络收集作者:咖啡不加糖人点击

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1.什么是哨兵
哨兵的作用就是对Redis的系统的运行情况的监控,它是一个独立进程。它的主要功能如下


监控主数据库和从数据库是否运行正常
主数据出现故障后自动将从数据库转化为主数据库

2.实现原理


单个哨兵的架构
【Redis】的哨兵(sentinel)详解


多个哨兵的架构
【Redis】的哨兵(sentinel)详解


多个哨兵,不仅同时监控主从数据库,而且哨兵之间互为监控。


3.环境
当前处于一主多从的环境中


【Redis】的哨兵(sentinel)详解


4.配置哨兵
启动哨兵进程首先需要创建哨兵配置文件:


vim sentinel.conf
输入内容:
sentinel monitor taotaoMaster 127.0.0.1 6379 1
说明:
taotaoMaster:监控主数据的名称,自定义即可,可以使用大小写字母和“.-_”符号
127.0.0.1:监控的主数据库的IP
6379:监控的主数据库的端口
1:最低通过票数

启动哨兵进程:
redis-sentinel ./sentinel.conf


【Redis】的哨兵(sentinel)详解


由上图可以看到:


哨兵已经启动,它的id为9059917216012421e8e89a4aa02f15b75346d2b7
为master数据库添加了一个监控
发现了2个slave(由此可以看出,哨兵无需配置slave,只需要指定master,哨兵会自动发现slave)

5.从数据库宕机
【Redis】的哨兵(sentinel)详解


kill掉2626进程后,30秒后哨兵的控制台输出:


2989:X 05 Jun 20:09:33.509 # +sdown slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster 127.0.0.1 6379


说明已经监控到slave宕机了,那么,如果我们将6380端口的redis实例启动后,会自动加入到主从复制吗?


2989:X 05 Jun 20:13:22.716 * +reboot slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster 127.0.0.1 6379
2989:X 05 Jun 20:13:22.788 # -sdown slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster 127.0.0.1 6379


可以看出,slave从新加入到了主从复制中。-sdown:说明是恢复服务。


【Redis】的哨兵(sentinel)详解


6.主库宕机
哨兵控制台打印出如下信息:


2989:X 05 Jun 20:16:50.300 # +sdown master taotaoMaster 127.0.0.1 6379说明master服务已经宕机
2989:X 05 Jun 20:16:50.300 # +odown master taotaoMaster 127.0.0.1 6379 #quorum 1/1
2989:X 05 Jun 20:16:50.300 # +new-epoch 1
2989:X 05 Jun 20:16:50.300 # +try-failover master taotaoMaster 127.0.0.1 6379开始恢复故障
2989:X 05 Jun 20:16:50.304 # +vote-for-leader 9059917216012421e8e89a4aa02f15b75346d2b7 1投票选举哨兵leader,现在就一个哨兵所以leader就自己
2989:X 05 Jun 20:16:50.304 # +elected-leader master taotaoMaster 127.0.0.1 6379选中leader
2989:X 05 Jun 20:16:50.304 # +failover-state-select-slave master taotaoMaster 127.0.0.1 6379 选中其中的一个slave当做master
2989:X 05 Jun 20:16:50.357 # +selected-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ taotaoMaster 127.0.0.1 6379选中6381
2989:X 05 Jun 20:16:50.357 * +failover-state-send-slaveof-no one slave 127.0.0.1:6381 127.0.0.1 6381 @ taotaoMaster 127.0.0.1 6379发送slaveof no one命令
2989:X 05 Jun 20:16:50.420 * +failover-state-wait-promotion slave 127.0.0.1:6381 127.0.0.1 6381 @ taotaoMaster 127.0.0.1 6379 等待升级master
2989:X 05 Jun 20:16:50.515 # +promoted-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ taotaoMaster 127.0.0.1 6379升级6381为master
2989:X 05 Jun 20:16:50.515 # +failover-state-reconf-slaves master taotaoMaster 127.0.0.1 6379
2989:X 05 Jun 20:16:50.566 * +slave-reconf-sent slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster 127.0.0.1 6379
2989:X 05 Jun 20:16:51.333 * +slave-reconf-inprog slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster 127.0.0.1 6379
2989:X 05 Jun 20:16:52.382 * +slave-reconf-done slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster 127.0.0.1 6379
2989:X 05 Jun 20:16:52.438 # +failover-end master taotaoMaster 127.0.0.1 6379 故障恢复完成
2989:X 05 Jun 20:16:52.438 # +switch-master taotaoMaster 127.0.0.1 6379 127.0.0.1 6381主数据库从6379转变为6381
2989:X 05 Jun 20:16:52.438 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster 127.0.0.1 6381添加6380为6381的从库
2989:X 05 Jun 20:16:52.438 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster 127.0.0.1 6381添加6379为6381的从库
2989:X 05 Jun 20:17:22.463 # +sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster 127.0.0.1 6381 发现6379已经宕机,等待6379的恢复


【Redis】的哨兵(sentinel)详解


可以看出,目前,6381位master,拥有一个slave为6380.


接下来,我们恢复6379查看状态:
2989:X 05 Jun 20:35:32.172 # -sdown slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster 127.0.0.1 63816379已经恢复服务
2989:X 05 Jun 20:35:42.137 * +convert-to-slave slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster 127.0.0.1 6381将6379设置为6381的slave


【Redis】的哨兵(sentinel)详解


7.配置多个哨兵


vim sentinel.conf
输入内容:
sentinel monitor taotaoMaster 127.0.0.1 6381 2
sentinel monitor taotaoMaster2 127.0.0.1 6381 1

3451:X 05 Jun 21:05:56.083 # +sdown master taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:56.083 # +odown master taotaoMaster2 127.0.0.1 6381 #quorum 1/1
3451:X 05 Jun 21:05:56.083 # +new-epoch 1
3451:X 05 Jun 21:05:56.083 # +try-failover master taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:56.086 # +vote-for-leader 3f020a35c9878a12d2b44904f570dc0d4015c2ba 1
3451:X 05 Jun 21:05:56.086 # +elected-leader master taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:56.086 # +failover-state-select-slave master taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:56.087 # +sdown master taotaoMaster 127.0.0.1 6381
3451:X 05 Jun 21:05:56.189 # +selected-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:56.189 * +failover-state-send-slaveof-noone slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:56.252 * +failover-state-wait-promotion slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:57.145 # +promoted-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:57.145 # +failover-state-reconf-slaves master taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:57.234 * +slave-reconf-sent slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:58.149 * +slave-reconf-inprog slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:58.149 * +slave-reconf-done slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:58.203 # +failover-end master taotaoMaster2 127.0.0.1 6381
3451:X 05 Jun 21:05:58.203 # +switch-master taotaoMaster2 127.0.0.1 6381 127.0.0.1 6380
3451:X 05 Jun 21:05:58.203 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ taotaoMaster2 127.0.0.1 6380
3451:X 05 Jun 21:05:58.203 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ taotaoMaster2 127.0.0.1 6380


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