使用keepalived 实现redis主从高可用

keepalived官方有中文文档:LVS + Keepalived Chinese application doc - March 16, 2010。

keepalived 实现VRRP协议,从路由级别实现VIP切换,可以完全避免类似heartbeat 脑裂问题。可以很nice的实现主从、主备、互备方案,尤其是无状态业务,有状态业务就需要额外花些功夫了。

     既然mysql 可以使用keepalived很好的做到主从切换,redis自然也就有样学样就成了。

redis主从实现完全没有mysql成熟,仅仅是可用而已,按照作者规划相应改进需要等3.0以后了。经过测试主从也不是那么完 全不靠谱。主要问题在于同步连接断开之后需要重新全量同步,如果频繁进行会对主服务带来很大性能影响。 但现实中主从机器往往要求放在一个机柜同一台交换设备下,网络闪断情况极低;再者主从同步在同步数量量大情况下,需要将缓存区调得足够大,不然也容易造成 连接断开。

实现切换逻辑如下:A B两台机器

1. A 、B 依次启动,A作为主、B为从

2.主A 挂掉,B接管业务,作为主

3.A 起来,作为从SLAVEOF B

4.B 挂掉,A 切回主

将一台全部作为主,即可实现主从,可做读写分离;也可以一台机器上多个实例一半主、一半从,实现互备份,两机同时接管业务,一台宕机后业务都集中在一台上。

   在keepalived 有两个角色:Master(一个)、Backup(多个),如果设置一个为Master,但Master挂了后再起来,必然再次业务又一次切换,这对于有 状态服务是不可接受的。解决方案就是两台机器都设置为Backup,而且优先级高的Backup设置为nopreemt 不抢占。

   安装比较简单:

需要依赖包:openssl-devel(ubuntu 中为 libssl-dev),popt-devel (ubuntu中为libpopt-dev),redheat中都已经有了。

  配置文件默认路径:/etc/keepalived/keepalived.conf 也可以手动指定路径,不过要注意的是手动指定需要使用绝对路径。
  使用keepalived -D 运行,即可启动3个守护进程:一个父进程,一个check健康检查,一个Vrrp,-D将日志写入/var/log/message 
 

配置如下:

   主:

使用keepalived 实现redis主从高可用
! Configuration File for keepalived

global_defs {
   router_id test
}
vrrp_script chk_redis 
{ 
     script "/etc/keepalived/scripts/redis_check.sh 127.0.0.1 7001" 
     interval 2 
     timeout 2
     fall 3
}
vrrp_script chk_redis2 
{ 
     script "/etc/keepalived/scripts/redis_check.sh 127.0.0.1 7002"
     interval 2
     timeout 2
     fall 3
}

vrrp_instance redis {
    state BACKUP # 主也配置为SLAVE
    interface wlan0}  
    virtual_router_id 51 
    priority  150       
    nopreempt # 不抢占,注意加上
    advert_int 1        
    authentication {   
        auth_type PASS   
        auth_pass lulu
    }
    virtual_ipaddress {  
    192.168.1.144
    }
    track_script { 
         chk_redis 
    } 
    notify_master "/etc/keepalived/scripts/redis_master_slave.sh 127.0.0.1 192.168.1.126 7001"
    notify_backup "/etc/keepalived/scripts/redis_backup_slave.sh 127.0.0.1 192.168.1.126 7001"
    notify_fault /etc/keepalived/scripts/redis_fault.sh 
    notify_stop /etc/keepalived/scripts/redis_stop.sh 
}

vrrp_instance redis2 {
    state BACKUP  
    interface wlan0 }  
    virtual_router_id 50 
    priority 150         
    advert_int 1         
    nopreempt
    authentication {      
        auth_type PASS  
        auth_pass lulu
    }
    virtual_ipaddress {  
    192.168.1.145
    }
    track_script { 
         chk_redis2 
    } 
   notify_master "/etc/keepalived/scripts/redis_master_slave.sh 127.0.0.1 192.168.1.126 7002"
    notify_backup "/etc/keepalived/scripts/redis_backup_slave.sh 127.0.0.1 192.168.1.126 7002"
    notify_fault /etc/keepalived/scripts/redis_fault.sh 
    notify_stop /etc/keepalived/scripts/redis_stop.sh 
}
使用keepalived 实现redis主从高可用

备:

使用keepalived 实现redis主从高可用
! Configuration File for keepalived

global_defs {
   router_id test
}
vrrp_script chk_redis 
{ 
     script "/etc/keepalived/scripts/redis_check.sh 127.0.0.1 7001" 
     interval 2
     timeout 2
     fall 3
}
vrrp_script chk_redis2 
{ 
     script "/etc/keepalived/scripts/redis_check.sh 127.0.0.1 7002" 
     interval 2
     timeout 2
     fall 3
}

vrrp_instance redis {
    state BACKUP   
    interface wlan0 }  
    virtual_router_id 51  
    priority  100       
    advert_int 1        
    authentication {    
        auth_type PASS   
        auth_pass test
    }
    virtual_ipaddress { 
    192.168.1.144
    }
    track_script { 
         chk_redis 
    } 
    notify_master "/etc/keepalived/scripts/redis_master_slave.sh 127.0.0.1 192.168.1.126 7001"
    notify_backup "/etc/keepalived/scripts/redis_backup_slave.sh 127.0.0.1 192.168.1.126 7001"
    notify_fault /etc/keepalived/scripts/redis_fault.sh 
    notify_stop /etc/keepalived/scripts/redis_stop.sh 
}

vrrp_instance redis2 {
    state BACKUP   
    interface wlan0 }  
    virtual_router_id 50  
    advert_int 1      
    priority 100
    authentication {   
        auth_type PASS  
        auth_pass test
    }
    virtual_ipaddress {   
    192.168.1.145
    }
    track_script { 
         chk_redis2
    } 
   notify_master "/etc/keepalived/scripts/redis_master_slave.sh 127.0.0.1 192.168.1.126 7002"
    notify_backup "/etc/keepalived/scripts/redis_backup_slave.sh 127.0.0.1 192.168.1.126 7002"
    notify_fault /etc/keepalived/scripts/redis_fault.sh 
    notify_stop /etc/keepalived/scripts/redis_stop.sh 
}
使用keepalived 实现redis主从高可用

其他脚本见附件:http://files.cnblogs.com/lulu/scripts.rar