前面讲到了部署多个tomcat和多个rabbitmq用nginx做代理服务器，这种情况，tomcat和rabbitmq既实现了高可用又实现了负载均衡。但是，nginx确成了单点。在一个HA环境中，任何一个点都必须实现高可用，这里就需要借助keepalived来实现nginx的高可用。

测试环境

• host1 192.168.30.1 (nginx, keepalived/master)
• host2 192.168.30.2 (nginx, keepalived/backup)

安装keepalived

host1和host2分别安装keepalived, host2安装nginx(过程略)

$ yum install keepalived

准备nginx状态检测脚本

/etc/keepalived/check_nginx.sh

#!/bin/bash
if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" == "" ]
then
 /usr/local/nginx/sbin/nginx
 sleep 5
 if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" == "" ]
 then
 killall keepalived
 fi
fi

拷贝到host2

$ scp /etc/keepalived/check_nginx.sh root@192.168.30.2:/etc/keepalived/check_nginx.sh 

修改host1的keepalived配置

 ! Configuration File for keepalived

global_defs {
   notification_email {
     test@sanlogic.com             
   }
   notification_email_from  test@test.com 
   smtp_server 127.0.0.1                             
   smtp_connect_timeout 30                  
   router_id LVS_DEVEL      
}

vrrp_script chk_nginx {
    script "/etc/keepalived/check_nginx.sh"
    interval 2
    weight 2
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_nginx
    }
    virtual_ipaddress {
        192.168.30.30
     }
}

修改host2的keepalived配置文件

 ! Configuration File for keepalived

global_defs {
   notification_email {
     test@sanlogic.com
   }
   notification_email_from  test@test.com
   smtp_server 127.0.0.1 
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}

vrrp_script chk_nginx {
    script "/etc/keepalived/check_nginx.sh"
    interval 2
    weight 2
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 50
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_nginx
    }
    virtual_ipaddress {
        192.168.30.30
     }
}

启动keepalived

$ systemctl enable keepalived
$ systemctl start keepalived

测试

用浏览器访问http://192.168.30.30/hellonginx，出现如下界面

这时关闭host1

$ halt -p

用浏览器访问http://192.168.30.30/hellonginx，仍然是如下界面

Done !