Keepalived实现VIP

主的配置：

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# master
# /etc/keepalived/master/keepalived.conf
vrrp_script chk_nginx {
    script "/etc/keepalived/master/check_local.sh"
    interval 5
}
vrrp_instance VI_1 {
    interface em2
    state MASTER
    #state BACKUP
    #nopreempt
    virtual_router_id 50
    priority 100
    advert_int 1

    track_interface {
        em1
    }
    authentication {
        auth_type PASS
        auth_pass sss23234d
    }
    track_script {
        chk_nginx
    }
    virtual_ipaddress {
        210.14.xxx.xxx/32 dev em1 label em1:1
        10.10.xxx.xxx/16 dev em2 label em2:1
    }

    notify_master "/etc/keepalived/master/notify_master.sh"
    notify_backup "/etc/keepalived/master/notify_backup.sh"
    notify_fault  "/etc/keepalived/master/notify_backup.sh"
    notify_stop   "/etc/keepalived/master/notify_backup.sh"
}

从的配置：

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# slave
# /etc/keepalived/slave/keepalived.conf
vrrp_script chk_nginx {
    script "/etc/keepalived/slave/check_local.sh"
    interval 5
}
vrrp_instance VI_1 {
    interface eth1
    state BACKUP
    #state BACKUP
    #nopreempt
    virtual_router_id 50
    priority 99
    advert_int 1

    track_interface {
        eth0
        eth1
    }
    authentication {
        auth_type PASS
        auth_pass sss23234d
    }
    track_script {
        chk_nginx
    }
    virtual_ipaddress {
        210.14.xxx.xxx/32 dev eth0 label eth0:1
        10.10.xxx.xxx/16 dev eth1 label eth1:1
    }

    notify_master "/etc/keepalived/slave/notify_master.sh"
    notify_backup "/etc/keepalived/slave/notify_backup.sh"
    notify_fault  "/etc/keepalived/slave/notify_backup.sh"
    notify_stop   "/etc/keepalived/slave/notify_backup.sh"
}

说明：

上面如果将主从都写成下面的配置：

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...
state BACKUP
nopreempt
...

这样的配置意味着没有主从之分了，谁先接管服务，只要服务不挂，另外一台起来了也没用，不会发生VIP的转移切换。

check_local.sh

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#!/bin/bash

RET=`ps awx|grep "nginx_api/nc_api.conf" |grep -v grep`
if [ -z "$RET" ];then
    sh /home/bmc/website/nginx_api/restart_nginx_api.sh
    #sleep 1
    #RET2=`ps awx|grep "nginx_api/nc_api_and_web" |grep -v grep`
    #if [ -z "$RET2" ];then
    #    killall keepalived
    #fi
fi
exit 0

restart_keepalived.sh

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#!/bin/bash

killall keepalived
keepalived -D -f /etc/keepalived/master/keepalived.conf

几个需要注意的问题

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# 有下面的日志
Opening file '/etc/keepalived/master/keepalived.conf'.
NOTICE: setting config option max_auto_priority should result in better keepalived performance

# 新版的参考
global_defs {
   router_id fundtxjslave
   script_user root
   enable_script_security
   max_auto_priority 1 # 禁止上面的NOTICE->max_auto_priority
}
vrrp_script chk_script {
    script "/etc/keepalived/slave/check_local.sh"
    interval 6
    fall 3
    rise 1
    weight -5
}
vrrp_instance VI_1 {
    interface eno1
    state BACKUP
    nopreempt
    virtual_router_id 59
    priority 99
    advert_int 2 # 心跳间隔的秒数

    track_interface {
        eno2
    }
    authentication {
        auth_type PASS
        auth_pass wxtl232
    }
    track_script {
        chk_script
    }
    virtual_ipaddress {
        211.19.x.x/27 dev eno1 label eno1:174
        10.10.x.x/24 dev eno2 label eno2:174
    }
    notify_master "/etc/keepalived/slave/notify_master.sh"
    notify_backup "/etc/keepalived/slave/notify_backup.sh"
}

Keepalived脑裂问题

keepalived是软件级别的浮动IP方案，在使用过程中存在两台主机同时得到VIP的情况，此时请求访问那台服务器是未知的。如果应用是无状态的服务接口还好，但如果服务器上部署的是有状态的数据库服务器，将可能导致数据错乱，两台服务器数据不一致等严重的问题。

要想实现这种系统的高可用方案，可以考虑硬件级别的HA方案；或者在没那个严苛的场合，自己写脚本监控Keepalived软件，防止两台服务器同时获得VIP。

（完）