用Keepalived搭建双Nginx server集群，防止单点故障
用Keepalived搭建双Nginx server集群，防止单点故障综述：
浏览器访问虚拟IP: 192.168.1.57, 该虚拟IP被Keepalived接管，两个Keepalived进程分别运行在物理IP为192.168.1.56和192.168.1.59服务器上，这两个服务器上都运行着Nginx server。Nginx server都监听虚拟IP 192.168.1.57. Nginx背后有一些web app集群，已经配置成upstream.
为了防止Nginx自己成为单点瓶颈，这里采用了双Nginx server的方式。每个Server都是Ubuntu 12.04.
假定我的第一台Ubuntu server物理IP地址是192.168.1.56，已经安装了Nginx server，现在安装Keepalived，后面称这台为master server.apt-get install keepalived另外一台Ubuntu server物理IP是192.168.1.59, 也安装Nginx server和Keapalived. 后面称这台为backup server. Nginx的安装以及配置不是本文关注内容，请参考我的IT论坛文章。现在开始配置master server. 安装完成keepalived后，通过查看脚本/etc/init.d/keepalived里面发现，启动配置文件的路径是CONFIG=/etc/keepalived/keepalived.conf 但是该文件现在还不存在。所以我创建一个，内容如下：# Settings for notifications
global_defs {
notification_email {
csfreebird@gmail.com # Email address for notifications
}
notification_email_from keepalived@your_company.com# The from address for the notifications
smtp_server 127.0.0.1
smtp_connect_timeout 15
}
# Define the script used to check if haproxy is still working
vrrp_script chk_http_port {
script "/etc/keepalived/check_nginx.sh" # check Nginx is alive or not
interval 2 #
weight 2
}
# Configuation for the virtual interface
vrrp_instance VI_1 {
interface eth0
state MASTER # set this to BACKUP on the other machine
priority 101 # set this to 100 on the other machine
virtual_router_id 51
smtp_alert # Activate email notifications
authentication {
auth_type PASS
auth_pass 1111 # Set this to some secret phrase
}
# The virtual ip address shared between the two loadbalancers
virtual_ipaddress {
192.168.1.57
}
# Use the script above to check if we should fail over
track_script {
chk_http_port
}
}
说明：1. smtp_server必须要用127.0.0.1
2. 自己要创建一个检查nginx进程的脚本!/bin/bash
# try to start nginx if nginx process is dead
# shutdonw keepalived process if start nginx failed
pid=`ps -C nginx --no-header |wc -l`
if [ $pid -eq 0 ];then
service nginx start
sleep 3
if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
service keepalived stop
fi
fi
3. 修改nginx的所有server配置，将server_name都改为虚拟IPserver_name192.168.1.57;4. 注意，这里的虚拟IP不是用修改/etc/network/interfaces的方式，而是在keepalived配置文件中直接设置，要想判断是否成功，直接ping 就行了，ifconfig是看不到的。ping 192.168.1.57
PING 192.168.1.57 (192.168.1.57) 56(84) bytes of data.
64 bytes from 192.168.1.57: icmp_req=1 ttl=64 time=0.024 ms
64 bytes from 192.168.1.57: icmp_req=2 ttl=64 time=0.020 ms对192.168.1.59做相同的配置，略有变化的是：vrrp_instance VI_1 {
interface eth0
state BACKUP// changed
priority 100// changed通过轮流关闭master和backup，证明keepalived已经有效工作了。
参考资料：Keepalived官方文档真是够差的。
http://www.leaseweblabs.com/2011/09/setting-up-keepalived-on-ubuntu-load-balancing-using-haproxy-on-ubuntu-part-2/
http://blog.csdn.net/zmj_88888888/article/details/8825471
摘自：http://blog.csdn.net/csfreebird/article/details/11372247
用Keepalived搭建双Nginx server集群，防止单点故障
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