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[操作系统]Nginx+keepalive


规划和准备

两台相同配置的web

用途

IP

MASTER

192.168.1.100

BACKUP

192.1681.101

安装

两台接入服务器分别安装NginX和keepalived:

准备依赖包:

yum -y install gcc pcre-devel zlib-devel openssl-develyum -y install popt-devel

下载

wget http://nginx.org/download/nginx-1.2.4.tar.gz wget http://www.keepalived.org/software/keepalived-1.2.7.tar.gz

安装NginX

安装keepalive

tar zxvf keepalived-1.2.7.tar.gzcd keepalived-1.2.7./configuremake make installcp /usr/local/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/mkdir /etc/keepalivedcp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/cp /usr/local/sbin/keepalived /usr/sbin/

加入启动服务

echo "/usr/local/nginx/sbin/nginx" >> /etc/rc.localecho "/etc/init.d/keepalived start" >> /etc/rc.local

 配置

3.1 配置NginX

  两台接入服务器的NginX的配置完全一样,主要是配置/usr/local/nginx/conf/nginx.conf的http。其中多域名指向是通过虚拟主机(配置http下面的server)实现;同一域名的不同虚拟目录通过每个server下面的不同location实现;到后端的服务器在http下面配置upstream,然后在server或location中通过proxypass引用。要实现前面规划的接入方式,http的配置如下:

http {  include    mime.types;  default_type application/octet-stream;  sendfile    on;  upstream dev.hysec.com {    server 50.1.1.21:80;  }  upstream opslinux.com {   ip_hash;   server 192.168.1.102:80   server 192.168.1.103:80   server 192.168.1.104:80  }  server {    listen    80;    server_name opslinux.com;    location / {      proxy_pass http://opslinux.com;    }}

验证方法:

首先用IP访问前表中各个应用服务器的url

再用域名和路径访问前表中各个应用系统的域名/虚拟路径

3.2 配置keepalived

按照上面的安装方法,keepalived的配置文件在/etc/keepalived/keepalived.conf。主、从服务器的配置相关联但有所不同。如下:

Master:! Configuration File for keepalivedglobal_defs { router_id NGINX_DEVEL}vrrp_instance VI_1 {  state MASTER  interface eth0  virtual_router_id 51  priority 101  advert_int 1  authentication {    auth_type PASS    auth_pass 1111  }  virtual_ipaddress {    192.168.1.100  }}Backup:! Configuration File for keepalivedglobal_defs { router_id NGINX_DEVEL}vrrp_instance VI_1 {  state BACKUP  interface eth0  virtual_router_id 51  priority 99  advert_int 1  authentication {    auth_type PASS    auth_pass 1111  }  virtual_ipaddress {    192.168.1.100  }}

验证:

先后在主、从服务器上启动keepalived: /etc/init.d/keepalived start

在主服务器上查看是否已经绑定了虚拟IP: ip addr

停止主服务器上的keepalived: /etc/init.d/keepalived stop 然后在从服务器上查看是否已经绑定了虚拟IP:

启动主服务器上的keepalived,看看主服务器能否重新接管虚拟IP

3.3 让keepalived监控NginX的状态

经过前面的配置,如果主服务器的keepalived停止服务,从服务器会自动接管VIP对外服务;一旦主服务器的keepalived恢复,会重新接管VIP。 但这并不是我们需要的,我们需要的是当NginX停止服务的时候能够自动切换。

keepalived支持配置监控脚本,我们可以通过脚本监控NginX的状态,如果状态不正常则进行一系列的操作,最终仍不能恢复NginX则杀掉keepalived,使得从服务器能够接管服务。

如何监控NginX的状态

最简单的做法是监控NginX进程,更靠谱的做法是检查NginX端口,最靠谱的做法是检查多个url能否获取到页面。

如何尝试恢复服务

如果发现NginX不正常,重启之。等待3秒再次校验,仍然失败则不再尝试。

根据上述策略很容易写出监控脚本。这里使用nmap检查nginx端口来判断nginx的状态,记得要首先安装nmap。监控脚本如下:

#!/bin/bash# check nginx server statusNGINX=/usr/local/nginx/sbin/nginxPORT=8080nmap localhost -p $PORT | grep "$PORT/tcp open"#echo $?if [ $? -ne 0 ];then  $NGINX -s stop  $NGINX  sleep 3  nmap localhost -p $PORT | grep "$PORT/tcp open"  [ $? -ne 0 ] && /etc/init.d/keepalived stopfi

不要忘了设置脚本的执行权限,否则不起作用。

假设上述脚本放在/opt/chk_nginx.sh,则keepalived.conf中增加如下配置:

主keepalivedvrrp_script chk_http_port {  script "/opt/chk_nginx.sh"  interval 1  weight -2}track_script {  chk_http_port}例子:! Configuration File for keepalivedglobal_defs {  router_id NGINX_UPSTEAM}vrrp_script chk_http_port {  script "/opt/chk_nginx.sh"  interval 1  weight -2}vrrp_instance VI_1 {  state MASTER  interface eth0  virtual_router_id 51  priority 100  advert_int 1  authentication {    auth_type PASS    auth_pass 1111  }  virtual_ipaddress {    192.168.1.100  }  track_script {  chk_http_port  }}

更进一步,为了避免启动keepalived之前没有启动nginx , 可以在/etc/init.d/keepalived的start中首先启动nginx:

start() {  /usr/local/nginx/sbin/nginx  sleep 3  echo -n $"Starting $prog: "  daemon keepalived ${KEEPALIVED_OPTIONS}  RETVAL=$?  echo  [ $RETVAL -eq 0 ] && touch /var/lock/subsys/$prog}