1、原理/需求 结合keepalived 对前端nginx实现HA； nginx进程基于Master+Slave(worker)多进程模型，自身具有非常稳定的子进程管理功能。在Master进程分配模式
1、原理/需求
结合keepalived 对前端nginx实现HA；
nginx进程基于Master+Slave(worker)多进程模型，自身具有非常稳定的子进程管理功能。在Master进程分配模式下，Master进程永远不进行业务处理，只是进行任务分发，从而达到Master进程的存活高可靠性，Slave(worker)进程所有的业务信号都由主进程发出，Slave(worker)进程所有的超时任务都会被Master中止，属于非阻塞式任务模型。
Keepalived是Linux下面实现VRRP备份路由的高可靠性运行件。基于Keepalived设计的服务模式能够真正做到主服务器和备份服务器故障时IP瞬间无缝交接。二者结合，可以构架出比较稳定的软件lb方案。
2、环境说明
192.168.2.4 keepalived nginx
192.168.2.5 keepalived nginx
虚拟IP (VIP)：192.168.2.6
3、安装keepalived和nginx
yum -y install openssl-develyum -y install libnl libnl-develyum install -y libnfnetlink-devel[root@master keepalived-1.3.9]# ./configure --prefix=/usr/local/keepalived[root@master keepalived-1.3.9]# make && make install[root@master ~]# mkdir /etc/keepalived[root@master ~]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/[root@master ~]# /usr/local/keepalived/sbin/keepalived -D4、配置MASTER keepalived
vim /etc/keepalived/keepalived.conf
! Configuration File for keepalivedglobal_defs {#标识本节点的名称 router_id master }vrrp_script chk_nginx { script "/etc/keepalived/nginx_check.sh" #每2秒检测一次nginx的运行状态 interval 2 #失败一次，将自己的优先级调整为-20 weight -20} vrrp_instance VI_1 { #状态，主节点为MASTER state MASTER #绑定VIP的网络接口 interface ens33 #虚拟路由的ID号，两个节点设置必须一样 virtual_router_id 51 #节点优先级，值范围0~254，MASTER>BACKUP priority 100 #组播信息发送时间间隔，两个节点必须设置一样，默认为1秒 advert_int 1 #设置验证信息，两个节点必须一致 authentication { auth_type PASS auth_pass 1111 } #虚拟IP，两个节点设置必须一致，可以设置多个 virtual_ipaddress { 192.168.1.106 } #nginx存活状态检测脚本 track_script { chk_nginx }}5、配置BACKUP keepalived
vim /etc/keepalived/keepalived.conf
! Configuration File for keepalivedglobal_defs { router_id backup}vrrp_script chk_nginx { script "/etc/keepalived/nginx_check.sh" interval 2 weight -20}vrrp_instance VI_1 { state BACKUP interface ens33 virtual_router_id 51 priority 99 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.1.106 } track_script { chk_nginx }}Tips：
state 参数值：主的是MASTER、备用的是BACKUP
priority 参数值： MASTER > BACKUP
virtual_router_id： 参数值要一样
调用的脚本nginx_check.sh
#!/bin/bash A=`ps -C nginx -no-header |wc -l` if [ $A -eq 1 ];then pkill keepalived fi 测试：
两台测试机4/5均启动keepalived和nginx
service keepalived restart
service keepalived nginx
验证nginx启动正常：
访问 master：http://192.168.2.4:80/
访问 backup: http://192.168.2.5:80/
查看keepalived的日志信息：
4/5均打开日志信息方便查看keepalived动态：
tail -f /var/log/messages
浏览器打开虚拟ip访问：http://192.168.2.6:80/ ，此时显示IP为192.168.2.4
服务器层的双机热备（比如服务器宕机、keepalived宕了）测试：
kill 192.168.2.4（master) 的keepalived进程
killall keepalived
4的日志信息如下：
Jun 11 18:03:10 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6 Jun 11 18:03:15 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6 Jun 11 19:30:44 localhost Keepalived: Terminating on signal Jun 11 19:30:44 localhost Keepalived: Stopping Keepalived v1.2.2 (06/10,2014) Jun 11 19:30:44 localhost Keepalived_vrrp: Terminating VRRP child process on signal Jun 11 19:30:44 localhost Keepalived_healthcheckers: Terminating Healthchecker child process on signal5的日志信息如下：
Jun 11 19:30:50 localhost Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs. Jun 11 19:30:50 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6 Jun 11 19:30:50 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.2.6 added Jun 11 19:30:55 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6刷新http://192.168.2.6:80/ ， 此时显示IP为192.168.2.5。
再次启动192.168.2.4的keepalived进程，192.168.2.4会自动接管成为master，192.168.2.5自动转为backup，从测试结果看，备机能成功接管，已经实现了热备。
