測試redis+keepalived實現簡單的主備切換

keepalived是一個是集羣管理中保證集羣高可用的一個服務軟件，它具備心跳檢測的功能。運用在redis上，則是具備主備切換的控制功能。

keepalived的主備切換方案的設計思想如下：

當 Master 與 Slave 均運作正常時, Master負責服務，Slave負責Standby；

當 Master 掛掉，Slave 正常時, Slave接管服務，同時關閉主從複製功能；

當 Master 恢復正常，則從Slave同步數據，同步數據之後關閉主從複製功能，恢復Master身份，於此同時Slave等待Master同步數據完成之後，恢復Slave身份。

然後依次循環。

下面就來大概講下實現過程：

環境準備

主：10.15.34.21

備：10.15.34.22

VIP(虛擬IP)：10.15.34.23，10.15.34.24

0.在主機和備機上分別創建用戶部署redis和keepalived,如用戶路徑：/home/cachedb

1.在主機和備機上安裝redis（過程略）；

2.在主機和備機上安裝keepalived(過程略)；

3.修改主機和備機上的keepalived的配置文件keepalived.conf（可將原有的配置文件備份成keepalived.conf.bak）

1）主機的keepalived配置：

! Configuration File for keepalived

global_defs {
   router_id LVS_REDIS_TEST_21
}

vrrp_script chk_redis_1 {
    script "/home/cachedb/redis/scripts/redis_check.sh 10.15.34.21 38001"
    interval 10
    timeout 2
    fall 3
}
vrrp_script chk_redis_2 {
    script "/home/cachedb/redis/scripts/redis_check.sh 10.15.34.21 38002"
    interval 10
    timeout 2
    fall 3
}


vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 40
    priority 150
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_redis_1
    }
    virtual_ipaddress {
        10.15.34.23 
    }
    notify_master "/home/cachedb/redis/scripts/redis_master.sh 10.15.34.21"
    notify_backup "/home/cachedb/redis/scripts/redis_backup.sh 10.15.34.21 38001 10.15.34.22 38001"
    notify_fault  "/home/cachedb/redis/scripts/redis_fault.sh"
    notify_stop   "/home/cachedb/redis/scripts/redis_stop.sh"
}

vrrp_instance VI_2 {
    state BACKUP
    interface eth0
    virtual_router_id 41
    priority 150
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_redis_2
    }
    virtual_ipaddress {
        10.15.34.54
    }
    notify_master "/home/cachedb/redis/scripts/redis_master.sh 10.15.34.21 38002"
    notify_backup "/home/cachedb/redis/scripts/redis_backup.sh 10.15.34.21 38002 10.15.34.22 38002"
    notify_fault  "/home/cachedb/redis/scripts/redis_fault.sh"
    notify_stop   "/home/cachedb/redis/scripts/redis_stop.sh"
}

2）備機的keepalived配置：

! Configuration File for keepalived

global_defs {
   router_id LVS_REDIS_TEST
}

vrrp_script chk_redis_1 {
    script "/home/cachedb/redis/scripts/redis_check.sh 10.15.34.22 38001"
    interval 10
    timeout 2
    fall 3
}
vrrp_script chk_redis_2 {
    script "/home/cachedb/redis/scripts/redis_check.sh 10.15.34.22 38002"
    interval 10
    timeout 2
    fall 3
}


vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 40
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_redis_1
    }
    virtual_ipaddress {
        10.15.34.33 
    }
    notify_master "/home/cachedb/redis/scripts/redis_master.sh 10.15.34.22 38001"
    notify_backup "/home/cachedb/redis/scripts/redis_backup.sh 10.15.34.22 38001 10.15.34.21 38001"
    notify_fault  "/home/cachedb/redis/scripts/redis_fault.sh"
    notify_stop   "/home/cachedb/redis/scripts/redis_stop.sh"
}

vrrp_instance VI_2 {
    state BACKUP
    interface eth0
    virtual_router_id 41
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_redis_2
    }
    virtual_ipaddress {
        10.15.34.34
    }
    notify_master "/home/cachedb/redis/scripts/redis_master.sh 10.15.34.22 38002"
    notify_backup "/home/cachedb/redis/scripts/redis_backup.sh 10.15.34.22 38002 10.15.34.21 38002"
    notify_fault  "/home/cachedb/redis/scripts/redis_fault.sh"
    notify_stop   "/home/cachedb/redis/scripts/redis_stop.sh"
}

注意：

a. 備機的keepalived配置的priority要比主機的低；

b. 備機不能有nopreempt屬性；

c. virtual_router_id 這個主備配置的要對應一致，並且在局域網要唯一，注意使用默認的ID如51時要check改ID有木有被佔用，若有就換一個。

d. interface eth0這個表名虛擬ip漂移的網卡爲eth0，注意應該確保主備都有網卡eth0（沒有的話也可以是eth1，eth2等）。可以用ifconfig來查看，並且主備都應該是相同的網卡eth~

配置完以後：

1）啓動主機的redis服務，再在root下啓動keepalived服務；

2）啓動備機的redis服務，再在root下啓動keepalived服務；

3）查看主機的角色：

./redis-cli -h 10.15.34.21 -p 38001

查看備機的角色：