Nginx + keepalived 双主

工作原理：

两台Nginx通过Keepalived生成两个实例，两台Nginx的VIP互为备份，任何一台Nginx机器如果发生硬件损坏，Keepalived会自动将它的VIP地址切换到另一台机器，不影响客户端的访问。

IP 信息列表：

VIP1 192.168.200.254 VIP2 192.168.200.253 Nginx1 192.168.200.202 Nginx2 192.168.200.203

在Nginx1/2上编译安装nginx服务

首先搭建Nginx1

[root@Nginx-1 ~]# yum -y install pcre-devel zlib-devel
[root@Nginx-1 ~]# useradd -M -s /sbin/nologin  nginx
[root@Nginx-1 ~]# tar xf nginx-1.6.2.tar.gz -C /usr/src
[root@Nginx-1 ~]# cd /usr/src/nginx-1.6.2
[root@Nginx-1 nginx-1.6.2]# ./configure --prefix=/usr/local/nginx --user=nginx --group=nginx && make && make install
[root@Nginx-1 nginx-1.6.2]# cd /usr/local/nginx/html/
[root@Nginx-1 html]# echo "server 192.168.200.202" > index.html
[root@Nginx-1 html]# /usr/local/nginx/sbin/nginx 
[root@Nginx-1 html]# netstat -anpt |grep nginx
tcp        0      0 0.0.0.0:80                  0.0.0.0:*                   LISTEN      4503/nginx  

搭建Nginx2， 同Nginx1搭建方式是一样的。与Nginx1唯一不同的是：

[root@Nginx-2 html]# echo "server 192.168.200.203" > index.html

在Nginx1/2上编译安装keepalived服务

[root@Nginx-1 ~]# yum -y install kernel-devel openssl-devel

[root@Nginx-1 ~]# tar xf keepalived-1.2.13.tar.gz 
[root@Nginx-1 ~]# cd keepalived-1.2.13
[root@Nginx-1 keepalived-1.2.13]# ./configure --prefix=/ --with-kernel-dir=/usr/src/kernels/2.6.18-194.el5-i686 && make && make install

[root@Nginx-1 ~]# chkconfig --add keepalived
[root@Nginx-1 ~]# chkconfig keepalived on
[root@Nginx-1 ~]# chkconfig --list keepalived
[root@Nginx-1 ~]# service keepalived start|stop    

修改keepalived配置文件

nginx1：

[root@Nginx-1 ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   notification_email {
        crushlinux@163.com
}
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 50
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123
    }
    virtual_ipaddress {
        192.168.200.254
    }
}

vrrp_instance VI_2 {
    state MASTER
    interface eth0 
    virtual_router_id 52
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123
    }
    virtual_ipaddress {
        192.168.200.253
    }
}

nginx2：

[root@Nginx-2 ~]# vim /etc/keepalived/keepalived.conf 
! Configuration File for keepalived

global_defs {
   notification_email {
        crushlinux@163.com
}
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}


vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123
    }
    virtual_ipaddress {
        192.168.200.254
    }
}

vrrp_instance VI_2 {
    state BACKUP
    interface eth0 
    virtual_router_id 52
    priority 50
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123
    }
    virtual_ipaddress {
        192.168.200.253
    }
}

nginx1：

[root@Nginx-1 ~]# service keepalived start
[root@Nginx-1 ~]# ip addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:2d:3d:97 brd ff:ff:ff:ff:ff:ff
    inet 192.168.200.202/24 brd 192.168.200.255 scope global eth0
    inet 192.168.200.254/32 scope global eth0
    inet6 fe80::20c:29ff:fe2d:3d97/64 scope link 
       valid_lft forever preferred_lft forever

nginx2：

[root@Nginx-2 ~]# service keepalived start
[root@Nginx-2 ~]# ip addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:6f:7d:87 brd ff:ff:ff:ff:ff:ff
    inet 192.168.200.203/24 brd 192.168.200.255 scope global eth0
    inet 192.168.200.253/32 scope global eth0
    inet6 fe80::20c:29ff:fe6f:7d87/64 scope link 
       valid_lft forever preferred_lft forever

client：

[root@client ~]# elinks --dump http://192.168.200.254
   server 192.168.200.202
[root@client ~]# elinks --dump http://192.168.200.253
   server 192.168.200.203

Nginx-1/2 二台机器都执行监控Nginx进程的脚本

[root@Nginx-1 ~]# cat nginx_pidcheck 
#!/bin/bash
while :
do
	nginxpid=`ps -C nginx --no-header | wc -l`
	if [ $nginxpid -eq 0 ]
	then
		/usr/local/nginx/sbin/nginx
		sleep 5
		nginxpid=`ps -C nginx --no-header | wc -l`
		echo $nginxpid
		if [ $nginxpid -eq 0 ]
		then
			/etc/init.d/keepalived stop
		fi
	fi
	sleep 5
done

[root@Nginx-1 ~]# nohup sh nginx_pidcheck &

这是执行无限循环的脚本，两台Nginx机器上都有执行此脚本，每隔5秒执行一次，用ps -C是命令来收集nginx的PID值到底是否为0，如果是0的话，即Nginx已经进程死掉，尝试启动nginx进程；如果继续为0，即Nginx启动失败，则关闭本机的Keeplaived服务，VIP地址则会由备机接管，当然了，整个网站就会全部由备机的Nginx来提供服务了，这样保证Nginx服务的高可用。

验证

脚本测试：

[root@Nginx-1 ~]# netstat -anpt |grep nginx
tcp        0      0 0.0.0.0:80                  0.0.0.0:*                   LISTEN      4321/nginx          
[root@Nginx-1 ~]# killall -s QUIT nginx
[root@Nginx-1 ~]# netstat -anpt |grep nginx
tcp        0      0 0.0.0.0:80                  0.0.0.0:*                   LISTEN      59418/nginx 

VIP转移测试：

[root@Nginx-1 ~]# ip addr show dev eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:2d:3d:97 brd ff:ff:ff:ff:ff:ff
    inet 192.168.200.202/24 brd 192.168.200.255 scope global eth0
    inet 192.168.200.254/32 scope global eth0
    inet6 fe80::20c:29ff:fe2d:3d97/64 scope link 
       valid_lft forever preferred_lft forever
	   
[root@Nginx-2 ~]# service keepalived stop
停止 keepalived：                                          [确定]

[root@Nginx-1 ~]# ip addr show dev eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:2d:3d:97 brd ff:ff:ff:ff:ff:ff
    inet 192.168.200.202/24 brd 192.168.200.255 scope global eth0
    inet 192.168.200.254/32 scope global eth0
    inet 192.168.200.253/32 scope global eth0
    inet6 fe80::20c:29ff:fe2d:3d97/64 scope link 
       valid_lft forever preferred_lft forever

[root@client ~]# elinks --dump http://192.168.200.254
   server 192.168.200.202
[root@client ~]# elinks --dump http://192.168.200.253
   server 192.168.200.202