使用 keepalived 的ip漂移搭建主从web

• keepalived 的原理请自行百度，这里利用其ip漂移功能，实现 主从web的高可用。

ip漂移指一个虚拟ip，在2个真实ip（主从机）之间漂移，外部访问这个虚拟ip。

达到的效果：主从机的web都开启服务。主机web宕机，从机web开始接管服务。等待主机开始服务后，主机开始对外服务，从机待命。

• 安装。

apt-get install keepalived或其他方式安装

• 配置

主机：

 

xlj@ubuntu:~$ cat /etc/keepalived/keepalived.conf 

global_defs {
   notification_email {
     [e-mail]
     [e-mail]
     [e-mail]
   }
   notification_email_from [e-mail]
   smtp_server 127.0.0.1
   smtp_connect_timeout 4
   router_id LVS_DEVEL
}

vrrp_script chk_nc {
    script "/home/xlj/check.sh"
    interval 6 
    weight -20
}

vrrp_instance VI_1 {
    state MASTER 
 
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1 
    
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.111.111
    }
    track_script {
        chk_nc  
    }
    #notify_master /home/yonyou/nchome0509xin/keepalive/start.sh
    #notify_backup /home/yonyou/nchome0509xin/keepalive/stop.sh
}

 从机：

xlj@ubuntu:~$ cat /etc/keepalived/keepalived.conf 

global_defs {
   notification_email {
     [e-mail]
     [e-mail]
     [e-mail]
   }
   notification_email_from [e-mail]
   smtp_server 127.0.0.1
   smtp_connect_timeout 4
   router_id LVS_DEVEL
}

vrrp_script chk_nc {
    script "/home/xlj/check.sh"
    interval 6 
    weight -20
}

vrrp_instance VI_1 {
    state BACKUP 
    interface eth0
    virtual_router_id 51
    priority 90 
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.111.111
    }
    track_script {
        chk_nc  
    }
    #notify_master /home/yonyou/nchome0509xin/keepalive/start.sh
    #notify_backup /home/yonyou/nchome0509xin/keepalive/stop.sh
}

 

配置提示：

1. state为 MASTER或BACKUP
2. virtual_router_id 2机要相同
3. authentication 为防止非法加入要求的授权，2机要相同。
4. virtual_ipaddress 为要虚拟的ip，2机相同。
5. track_script 是健康检查脚本配置，本例是调用check.sh判断。
6. 其他参数可以百度

其中，健康检查脚本主从机都相同：

 

 

xlj@ubuntu:~$ cat /home/xlj/check.sh 
#!/bin/bash
COUNT=1
COUNT=`ps -ef | grep java | grep -v grep | wc -l`
if [  $COUNT -gt  0 ] ; then
      exit 0
else
      exit 1
fi
xlj@ubuntu:~$ 

  意思是检查java进程是否存在，存在则返回0，代表ok。

 

 

• 启动 keepalived服务

主从机分别启动服务：service keepalived restart

• 查看keepalived日志。默认日志在 /var/log/syslog:

xlj@ubuntu:~$ tail -f /var/log/syslog
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Registering gratuitous ARP shared channel
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Opening file '/etc/keepalived/keepalived.conf'.
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Configuration is using : 69085 Bytes
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Registering Kernel netlink command channel
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Opening file '/etc/keepalived/keepalived.conf'.
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Configuration is using : 11714 Bytes
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Using LinkWatch kernel netlink reflector...
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Using LinkWatch kernel netlink reflector...
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: VRRP_Instance(VI_1) Entering BACKUP STATE
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: VRRP_Script(chk_nc) succeeded

 

 

• 然后就可以 实验了，反复启停主从机的web服务，观察了。

注意，访问的是虚拟ip：

http://192.168.111.111:8080/

 

 

• 提示：

web页面看不出到底访问的是主机还是从机，建议你的web应用提供一个页面针对主机还是从机显示不同的信息。