用Keepalived搭建双Nginx server集群,防止单点故障
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.
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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,请参考我的其他文章。
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
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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:
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# 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
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/etc/keepalived/check_nginx.sh
内容如下:
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!/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IP
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server_name 192.168.1.57;
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。
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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:
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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。