nginx+keepalive主从双机热备 + 自动切换解决方案

环境采集cenots 6.3 64位迷你安装，因为安装前，你需要做一些工作
yum install -y make wget
如果你愿意可以更新下系统，更换下yum源.
1.安装keepalive
官方最新版  keepalived-1.2.7
tar zxvf keepalived-1.2.7.tar.gz
cd keepalived-1.2.7
在此之前。请安装一下一些简单的工具
yum install -y gcc openssl-devel popt-devel
不然会编译不成功的。
然后
./configure
make && make install

cp /usr/local/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/
chmod +x /etc/init.d/keepalived
chkconfig --add keepalived
chkconfig keepalived on
mkdir /etc/keepalived
ln -s /usr/local/sbin/keepalived /usr/sbin/

2.安装nginx
nginx-1.2.5.tar.gz
tar zxvf  nginx-1.2.5.tar.gz
cd nginx-1.2.5
安装一下相关组件.
yum install -y pcre-devel
./configure --prefix=/usr/local/nginx --user=www --group=www  --with-http_stub_status_module --with-http_ssl_module
make && make install

3.配置keepalive
两台服务器端keepalived.conf内容都为如下，都设置为backup，不抢占，注意修改优先级不同,更详细的keepalived配置文件说明可以执行man keepalived.conf查看：

! Configuration File for keepalived
global_defs {
   notification_email {
    admin@lvtao.net
        }
   notification_email_from admin@lvtao.net
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}
#监控服务.NGINX mysql等
vrrp_script chk_nginx {
    script "/home/check_nginx.sh"
    interval 2
    weight 2
}

vrrp_instance VI_1 {
    state BACKUP  #主从设置 MASTER
    interface eth2  #网卡名
    virtual_router_id 51
    mcast_src_ip 10.0.1.133 #本机IP
    priority 50  #从机小于主机
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass chtopnet
    }
    virtual_ipaddress {
        10.0.1.2  #VIP 的IP
    }
    track_script {
        chk_nginx  #检测脚本
    }

}

virtual_server 10.0.1.2 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 10.0.1.132 80 {
        weight 3
        TCP_CHECK {
            connect_timeout 10
            nb_get_retry 3
            delay_before_retry 3
            connect_port 80
        }
    }
    real_server 10.0.1.133 80 {
        weight 3
        TCP_CHECK {
            connect_timeout 10
            nb_get_retry 3
            delay_before_retry 3
            connect_port 80
        }
    }
}

启动相关服务。我在这儿使用的是nginx ，每个上面开了一个站点，通过IP可以直接访问的。启动keepalive后，就可以通过VIP的虚拟IP 10.0.1.2来访问站点了，测试方法就是停止任何其中一个站点，看它是否能自动切换到从服务器上。

上面代码中 nginx的检测脚本如下：

#!/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

在两台Web Server上执行realserver.sh脚本，为lo:0绑定VIP地址10.0.1.2、抑制ARP广播。

#!/bin/bash
#description: Config realserver

VIP=10.0.1.2

/etc/rc.d/init.d/functions

case "$1" in
start)
       /sbin/ifconfig lo:0 $VIP netmask 255.255.255.255 broadcast $VIP
       /sbin/route add -host $VIP dev lo:0
       echo "1" >/proc/sys/net/ipv4/conf/lo/arp_ignore
       echo "2" >/proc/sys/net/ipv4/conf/lo/arp_announce
       echo "1" >/proc/sys/net/ipv4/conf/all/arp_ignore
       echo "2" >/proc/sys/net/ipv4/conf/all/arp_announce
       sysctl -p >/dev/null 2>&1
       echo "RealServer Start OK"
       ;;
stop)
       /sbin/ifconfig lo:0 down
       /sbin/route del $VIP >/dev/null 2>&1
       echo "0" >/proc/sys/net/ipv4/conf/lo/arp_ignore
       echo "0" >/proc/sys/net/ipv4/conf/lo/arp_announce
       echo "0" >/proc/sys/net/ipv4/conf/all/arp_ignore
       echo "0" >/proc/sys/net/ipv4/conf/all/arp_announce
       echo "RealServer Stoped"
       ;;
*)
       echo "Usage: $0 {start|stop}"
       exit 1
esac

exit 0

分别在主从机上执行 sh realserver.sh start 就可实现负载均衡及高可用集群了；

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