什么是redis sentinel
参考文档:https://redis.io/topics/sentinel
简单的来说，就是Redis Sentinel 为redis 提供高可用性，主要体现在下面几个方面:
1.监控:redis sentinel会不间断的监控主服务器和从服务器是否正常工作
2.通知:当出现问题时，sentinel可以通过API通知系统管理员以及另外的服务器
3.自动故障转移:如果主服务器出现故障，sentinel可以启动故障转移，将其中一台从服务器升级为主服务器，其他的从服务器会重新配置为新主服务器 4.提供配置:sentinel充当客户端发现权限来源，客户端连接到sentinel询问负责给定服务器当前redis主服务器地址，如果发生故障，sentinel将报告新地址
redis sentinel 模拟环境
模拟环境为:1主2从
========redis=================sentinel==========
master:127.0.0.1 6379 127.0.0.1 26379
slave1:127.0.0.1 6380 127.0.0.1 26380
slave2:127.0.0.1 6381 127.0.0.1 26381环境搭建
redis.conf配置
6379
# .conf | grep -Ev "^$|^#" bind 127.0.0.1 port daemonize yes pidfile /var/run/redis_6379.pid logfile "/root/redis/redis-6379.log" dbfilename dump-.rdb dir /root/redis ... #
6380
# .conf | grep -Ev "^$|^#" bind 127.0.0.1 port daemonize yes pidfile /var/run/redis_6380.pid logfile "/root/redis/redis-6380.log" dbfilename dump-.rdb dir /root/redis ... #
6381
# .conf | grep -Ev "^$|^#" bind 127.0.0.1 port daemonize yes pidfile /var/run/redis_6381.pid logfile "/root/redis/redis-6381.log" dbfilename dump-.rdb dir /root/redis ... #
sentinel.conf配置
6379/6380/6381
# cat sentinel-*.conf | grep -Ev "^#|^$" port daemonize yes logfile "/root/redis/sentinel-6379.log" dir "/tmp" sentinel monitor mymaster sentinel down-after-milliseconds mymaster sentinel parallel-syncs mymaster sentinel failover-timeout mymaster #
启动redis server 和 sentinel
redis: # redis-server /etc/redis_6379.conf # redis-server /etc/redis_6380.conf # redis-server /etc/redis_6381.conf sentinel: # redis-sentinel /etc/sentinel-.conf # redis-sentinel /etc/sentinel-.conf # redis-sentinel /etc/sentinel-.conf
配置主从复制
# redis-cli -p > SLAVEOF OK > exit # redis-cli -p > SLAVEOF OK > exit
模拟故障迁移
首先，kill 掉redis master进程
# | $n ;done;
分析log
首先，redis 从服务器首先发现redis master 服务器无法连接，报错如下:
# *.log ==> redis-.log <== :S Nov ::54.235 # Connection with master lost. :S Nov ::54.235 * Caching the disconnected master state. ==> redis-.log <== :S Nov :: :S Nov ::54.466 * MASTER <-> SLAVE sync started :S Nov ::54.467 # Error condition on socket for SYNC: Connection refused ==> redis-.log <== :S Nov :: :S Nov ::54.782 * MASTER <-> SLAVE sync started :S Nov ::54.782 # Error condition on socket for SYNC: Connection refused ...
紧接着,redis sentinel 完成故障切换,从log来看，当6379主节点挂了之后，redis重新提了一个从节点6380为主节点，log 如下:
# *.log ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: #quorum / :X Nov :: :X Nov :: ==> sentinel-.log <== :X Nov :: #quorum / :X Nov :: :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: ==> sentinel-.log <== :X Nov :: :X Nov :: :X Nov :: @ mymaster :X Nov :: @ mymaster :X Nov :: @ mymaster :X Nov :: @ mymaster :X Nov :: :X Nov :: @ mymaster ==> sentinel-.log <== :X Nov :: @ mymaster :X Nov :: :X Nov :: @ mymaster :X Nov :: @ mymaster ==> sentinel-.log <== :X Nov :: @ mymaster :X Nov :: :X Nov :: @ mymaster :X Nov :: @ mymaster ==> sentinel-.log <== :X Nov :: :X Nov :: @ mymaster :X Nov :: @ mymaster :X Nov :: :X Nov :: :X Nov :: @ mymaster :X Nov :: @ mymaster ==> sentinel-.log <== :X Nov :: @ mymaster ==> sentinel-.log <== :X Nov :: @ mymaster ==> sentinel-.log <== :X Nov :: @ mymaster
再返回过来看redis server的log,此时可以看到6381为从节点已经向主节点6380请求并且完成了复制操作
==> redis-.log <== :M Nov :: asks for synchronization :M Nov :: accepted. Sending bytes of backlog starting from offset . ==> redis-.log <== :S Nov ::25.823 * Successful partial resynchronization with master. :S Nov ::25.823 # Master replication ID changed to 0288d040464ebccbb56dc56d54455434a406bcb2 :S Nov ::25.823 * MASTER <-> SLAVE sync: Master accepted a Partial Resynchronization.
当我们再启动6379服务器时，sentinel会让6379成为从库并且连接6380服务器,log如下:
启动6379服务器 # redis-server /root/redis/redis-.conf # *.log ... ==> sentinel-.log <== :X Nov :: @ mymaster ... # *.log ... ==> redis-.log <== :S Nov :: bytes from master :S Nov ::00.566 * MASTER <-> SLAVE sync: Flushing old data :S Nov ::00.566 * MASTER <-> SLAVE sync: Loading DB in memory :S Nov ::00.566 * MASTER <-> SLAVE sync: Finished with success ==> redis-.log <== :S Nov :: changes seconds. Saving... :S Nov :: :C Nov ::36.486 * DB saved on disk :C Nov :: MB of memory used by copy-on-write :S Nov ::36.569 * Background saving terminated with success ...
未完待续。。。