详解利用Keepalived+Nginx解决站点高可用性 推荐

背景：
公司官网PV不高，压力不大，所以公司给出两台服务器来提供官网web服务，毕竟是公司门面，不能出现问题！所以就需要一个轻量级web容灾方案！

方案：
利用keepalived+nginx实现官网web的高可用性
两台服务器一台为主，一台为备机，使两台机器公用一个虚拟IP，当主服务器宕机，106.3.32.6这个IP会自动切换到备机上，前端机恢复之后再自动切换回主服务机


然后，主服务机和备机利用rsync实现实时同步数据，
rsync的安装配置可以参照我之前的一篇文章：http://cuimk.blog.51cto.com/6649029/1322241

环境：
CentOS 6.4
nginx-1.2.1
keepalived-1.2.2
一、安装主和辅都需要安装keepalived,安装方法相同

yum -y install  kernel-devel
yum install openssl-* -y
wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz tar xzf keepalived-1.2.2.tar.gz
cd keepalived-1.2.2
./configure --prefix=/usr/local/keepalived
make && make install
ln -s /usr/src/kernels/2.6.18-238.el5-i686/ /usr/src/linux
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
mkdir -pv /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
ln -s /usr/local/keepalived/sbin/keepalived /sbin/

加入开机启动：chkconfigkeepalived on

二、配置主和辅配置的差别只在stateMASTER和priority 100vi /etc/keepalived/keepalived.conf

! Configuration File for keepalived
global_defs {
#   notification_email {    ####此处定义发生替换会邮件通知
#     cuimingkun@yinwuweiye.com
#   }
#   notification_email_from keepalived@domain.com
#   smtp_server 127.0.0.1
#   smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script chk_http_port {
script "/root/shell/nginx_pid.sh" ##监控脚本位置
interval 2
weight 2
}
track_script {
chk_http_port
}
vrrp_instance VI_1 {
state MASTER        #####备机为BACKUP
interface em1
virtual_router_id 51
priority 100        #####备机要小于主
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
106.3.32.6  ####虚拟IP
}
}

三、分别在主和辅服务器上建立nginx的监控脚本
Keepalived管理虚IP是通过组播和优先级实现的，优先级高的会拥有虚IP的管理权，所以要实现IP自动切换，只需要建立一个监控脚本，让keepalived进行调用，一旦发现nginx出现故障就kill掉keepalived的进程，让其他keepalived管理此IPvi /root/shell/nginx_pid.sh

#!/bin/bash
A=`ps -C nginx --no-header |wc -l`
if [ $A -eq 0 ];then
/usr/local/nginx/sbin/nginx
sleep 3
if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
killall keepalived
fi
fi

注意给脚本添加执行权限：chmod+x /root/shell/nginx_pid.sh两台机器启动keepalived：service keepalived start四、测试#ip a查看IP查看主的IP，目前虚IP在主这里


Kill掉主的keepalived,再查看，虚IP消失


查看辅的这边，可以看到虚IP


再启动主的keepalived，虚IP又回到主的这边



五、总结此方案没有做负载均衡，只是做了一个故障自动切换的处理，适用于PV不是很高的环境（当然Nginx做好调优其负载能力也是很强的），不过可以以同样的原理举一反三，把他做在高并发的负载均衡器上，来实现高必发的容灾方案！