keepalived实现nginx的高可用

    keepalived实现nginx HA的做法，首先参考博文http://quenlang.blog.51cto.com/4813803/1570352，搭建好nginx反向代理tomcat并利用自身模块proxy_cache实现web缓存的架构，该博文中的nginx安 装在hadoop1节点上，按照博文中的nginx的安装配置，配置好hadoop0，这样就有两个节点安装了nginx并实现了web缓存和反向代理。 这里hadoop0作为nginx的master，而hadoop1作为nginx的backup，以此来配置keepalived。

    在hadoop0、hadoop1上安装keepalived

yum install keepalived -y

    hadoop0上keepalived的配置如下

[root@hadoop0 ~]# cat  /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   notification_email {
     [email protected]
     [email protected]
     [email protected]
   }
   notification_email_from [email protected]
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}

vrrp_script check_nginx {
    script "/opt/check_nginx.sh"
    interval 2
}

vrrp_instance VI_2 {
    state MASTER
    interface eth0
    virtual_router_id 52
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }

    virtual_ipaddress {
        192.168.0.207
    }

    track_script {
        check_nginx
    }
}

    hadoop1上keepalived的配置如下

[root@hadoop1 ~]# cat  /etc/keepalived/keepalived.conf 
! Configuration File for keepalived

global_defs {
   notification_email {
     [email protected]
     [email protected]
     [email protected]
   }
   notification_email_from [email protected]
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}

vrrp_instance VI_2 {
    state BACKUP
    interface eth0
    virtual_router_id 52
    priority 80
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }

    virtual_ipaddress {
        192.168.0.207
    }
}

    从上面的配置看到，keepalived代理nginx实现HA之后的虚拟IP为192.168.0.207，监控nginx的脚本内容如下

[root@hadoop0 ~]# cat  /opt/check_nginx.sh 
#!/bin/bash
#author: kora
#date: 2014-10-21 
#description: check service such as nginx
#

#set -x

CHECK_TIME=3
NGINX_OK=1
NOW=`date`
STATUS='OK!'

procnum=`ps -ef |grep "/usr/local/nginx/sbin/nginx"|grep -v "grep"|wc -l`

while [ "$CHECK_TIME" -ne 0 ]
do
    let "CHECK_TIME-=1"
    if [ "$procnum" -eq 1 -a -f /usr/local/nginx/logs/nginx.pid ]
    then
        NGINX_OK=1
        CHECK_TIME=0
    else
        NGINX_OK=0
    fi
done

if [ "$NGINX_OK" -eq 0 ]
then 
    status='fail!'
    /etc/init.d/keepalived stop
fi

echo "$NOW:$STATUS" >> /usr/local/nginx/logs/keepalived.log
exit 0

    当master上的nginx挂掉之后，脚本会停调keepalived服务，从而将虚拟IP浮动到hadoop1上，实现高可用，而用户需要使用虚拟IP192.168.0.207来访问web应用。