LVS&&KeepAlived&&Nginx实现LB方案
相应概念部分：
LVS是Linux Virtual Server的简写，意即Linux虚拟服务器，是一个虚拟的服务器集群系统。
Keepalived作用是检测服务器的状态，如果有一台web服务器宕机，或工作出现故障，Keepalived将检测到，并将有故障的服务器从系统中剔除，同时使用其他服务器代替该服务器的工作，当服务器工作正常后Keepalived自动将服务器加入到服务器群中，这些工作全部自动完成，不需要人工干涉，需要人工做的只是修复故障的服务器。
服务器部署准备部分：
1）虚拟机4台
2）基础架构示意图
3）安装源文件下载地址
Keepalived&Nginx
软件安装步骤
在192.168.1.128及192.168.1.129上安装keepalived
在192.168.1.130及192.168.1.131上安装nginx
Keepalived安装步骤：
基础环境安装
yum install gcc
yum -y install openssl-devel
yum -y install libnl libnl-devel
yum install -y libnfnetlink-devel
yum -y install net-tools
yum install vim -y
源码安装
1）将keepalived安装包复制到/usr/local/src
2) 执行下列安装编译步骤
cd /use/local/src
tar -zxvf keepalived-2.0.10.tar.gz
mv keepalived-2.0.10 ../keepalived
cd /use/local/keepalived/
./configure
make && make install
3）keepalived配置部分
将keepalived配置文件拷贝到etc/keepalived下
mkdir /etc/keepalived
cp /usr/local/keepalived/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
设置Keepalived对应的开机启动服务
cp /usr/local/keepalived/keepalived/etc/init.d/keepalived /etc/rc.d/init.d/
cp /usr/local/keepalived/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/sbin/keepalived /usr/sbin/4）Keepalived 启动相关
service keepalived start|stop|restart
ipvsadm 安装步骤：
只需要在192.168.1.128及192.168.1.129上安装即可
yum install ipvsadm -yNginx 安装步骤：
进入到nginx 安装目录，执行yum install nginx-* -y
防火墙相关配置：
systemctl stop firewalld.service
systemctl stop iptables.service这边为了方便，直接采用关闭相关的防火墙进行操作
Keepalived&&Nginx对应的配置
Nginx相关配置：
首先，确定nginx已经处于启动状态；
cd /etc/init.d/
编辑脚本：
vim realserver
#虚拟的vip 根据自己的实际情况定义
SNS_VIP=192.168.1.200
/etc/rc.d/init.d/functions
case "$1" in
start)
ifconfig lo:0 $SNS_VIP netmask 255.255.255.255 broadcast $SNS_VIP
/sbin/route add -host $SNS_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)
ifconfig lo:0 down
route del $SNS_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
设置脚本对应权限
chmod 755 /etc/init.d/realserver
chmod 755 /etc/rc.d/init.d/functions
执行脚本启动： service realserver start
ip addr 查看VIP地址，出现对应的VIP地址，则表示配置成功
Keepalived配置部分：
cd /etc/keepalived
mv keepalived.conf keepalived-back.conf
vim keepalived.conf
备注：master 和 slave 配置有一定的差别
以下为Master的配置：
以下为Slave的配置：
配置注意事项：
router_id 后面跟的自定义的ID在同一个网络下是一致的
state state后跟的MASTER和BACKUP必须是大写；否则会造成配置无法生效的问题
interface 网卡ID， 采用ip a 进行查看
priority MASTER中配置的priority必须比BACKUP大；差值最好>=50
virtual_ipaddress 配置的VIP；允许配置多个
启动Keepalived； service Keepalived
检查Keepalived 启动之后配置情况；只在MASTER节点上出现对应的VIP，则为成功；
如果两个服务器均出现VIP地址， 则发生脑裂情况。
nginx配置调用其他服务接口配置DEMO大致如下：
upstream proxy-XX2 {
#ip_hash;
server 10.1.80.167:8080 weight=1 max_fails=3 fail_timeout=10s;
server 10.1.80.172:8080 weight=1 max_fails=3 fail_timeout=10s;
}
server {
listen 80;
server_name XX2.zhongbang.com;
access_log /data/log/nginx/XX2.access.log;
error_log /data/log/nginx/XX2.error.log;
location / {
proxy_pass http://proxy-XX2;
proxy_set_header Host $http_host;
#proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
最终访问服务均采用 域名的方式