Nginx+Keeplived双机热备(主从模式)

Nginx+Keeplived双机热备(主从模式)

参考资料：

http://www.cnblogs.com/kevingrace/p/6138185.html

双机高可用一般是通过虚拟IP(漂移IP)方法来实现的，基于Linux/Unix的IP别名技术。

双机高可用方法目前分为两种：

1．双机主从模式：即前端使用两台服务器，一台主服务器和一台热备服务器，正常情况下，主服务器绑定一个公网虚拟IP，提供负载均衡服务，热备服务器处于空闲状态；当主服务器发生故障时，热备服务器接管主服务器的公网虚拟IP，提供负载均衡服务；但是热备服务器在主机器不出现故障的时候，永远处于浪费状态，对于服务器不多的网站，该方案不经济实惠。

2．双机主主模式：即前端使用两台负载均衡服务器，互为主备，且都处于活动状态，同事各自绑定一个公网虚拟IP，提供负载均衡服务；当其中一台发生故障时，另一台接管发生故障服务器的公网虚拟IP(这时由非故障机器一台负担所有的请求)。这种方案，经济实惠，非常适合于当前架构环境。

今天再次分享下Nginx+keeplived实现高可用负载均衡的主从模式的操作记录：

keeplived可以认为是VRRP协议在Linux上的实现，主要有三个模块，分别是core，check和vrrp。

core模块为keeplived的核心，负责主进程的启动、维护以及全局配置文件的加载和解析。

check负责健康检查，包括创建的各种检查方式。

vrrp模块是来实现VRRP协议的。

一、环境说明

操作系统：CentOS release 6.9 (Final) minimal

web1：172.16.12.223

web2：172.16.12.224

vip：svn：172.16.12.226

svn：172.16.12.225

二、环境安装

安装nginx和keeplived服务(web1和web2两台服务器上的安装完全一样)。

2.1、安装依赖

yum  clean all
yum -y update
yum -y install gcc-c++ gd libxml2-devel libjpeg-devel libpng-devel net-snmp-devel wget telnet vim zip unzip
yum -y install curl-devel libxslt-devel pcre-devel libjpeg libpng libcurl4-openssl-dev
yum -y install libcurl-devel libcurl freetype-config freetype freetype-devel unixODBC libxslt
yum -y install gcc automake autoconf libtool openssl-devel
yum -y install perl-devel perl-ExtUtils-Embed
yum -y install cmake ncurses-devel.x86_64  openldap-devel.x86_64 lrzsz  openssh-clients gcc-g77  bison
yum -y install libmcrypt libmcrypt-devel mhash mhash-devel bzip2 bzip2-devel
yum -y install ntpdate rsync svn  patch  iptables iptables-services
yum -y install libevent libevent-devel  cyrus-sasl cyrus-sasl-devel
yum -y install gd-devel libmemcached-devel memcached git libssl-devel libyaml-devel auto make
yum -y groupinstall "Server Platform Development" "Development tools"
yum -y groupinstall "Development tools"
yum -y install gcc pcre-devel zlib-devel openssl-devel

2.2、Centos6系统安装完毕后，需要优化的地方

#关闭SELinux
sed -i 's/SELINUX=enforcing/SELinux=disabled/' /etc/selinux/config
grep SELINUX=disabled /etc/selinux/config
setenforce
getenforce
cat >> /etc/sysctl.conf << EOF
#
##custom
#
net.ipv4.ip_forward =
net.ipv4.conf.default.rp_filter =
net.ipv4.conf.default.accept_source_route =
kernel.sysrq =
kernel.core_uses_pid =
net.ipv4.tcp_syncookies =
kernel.msgmnb =
kernel.msgmax =
net.ipv4.tcp_max_tw_buckets =
net.ipv4.tcp_sack =
net.ipv4.tcp_window_scaling =
net.ipv4.tcp_rmem =
net.ipv4.tcp_wmem =
net.core.wmem_default =
net.core.rmem_default =
net.core.rmem_max =
net.core.wmem_max =
net.core.netdev_max_backlog =
net.core.somaxconn =
net.ipv4.tcp_max_orphans =
net.ipv4.tcp_max_syn_backlog =
net.ipv4.tcp_timestamps =
#net.ipv4.tcp_synack_retries =
net.ipv4.tcp_synack_retries =
#net.ipv4.tcp_syn_retries =
net.ipv4.tcp_syn_retries =
net.ipv4.tcp_tw_recycle =
net.ipv4.tcp_tw_reuse =
net.ipv4.tcp_mem =
#net.ipv4.tcp_fin_timeout =
net.ipv4.tcp_fin_timeout =
net.ipv4.tcp_keepalive_time =
net.ipv4.ip_local_port_range =
#net.ipv4.tcp_tw_len =
EOF

#使其生效
sysctl -p
cp /etc/security/limits.conf /etc/security/limits.conf.bak2017
cat >> /etc/security/limits.conf << EOF
#
###custom
#
*           soft   nofile
*           hard   nofile
*           soft   nproc
*           hard   nproc
EOF

2.3、修改shell终端的超时时间

vi /etc/profile 增加如下一行即可（3600秒,默认不超时）
cp   /etc/profile   /etc/profile.bak2017
cat >> /etc/profile << EOF
export TMOUT=
EOF

2.4、下载软件包

（master和slave两台负载均衡机都要做）
[root@web1 ~]# cd /usr/local/src/
 [root@web1 src]# wget http://nginx.org/download/nginx-1.9.7.tar.gz
 [root@web1 src]# wget http://www.keepalived.org/software/keepalived-1.3.2.tar.gz

2.5、安装nginx

（master和slave两台负载均衡机都要做）
[root@web1 src]# tar -zxvf nginx-1.9..tar.gz
[root@web1 nginx-1.9.]# cd nginx-1.9.
# 添加www用户，其中-M参数表示不添加用户家目录，-s参数表示指定shell类型
[root@web1 nginx-1.9.]# useradd www -M -s /sbin/nologin
[root@web1 nginx-1.9.]# vim auto/cc/gcc
#将这句注释掉 取消Debug编译模式 大概在179行
# debug
# CFLAGS="$CFLAGS -g"
[root@web1 nginx-1.9.]#  ./configure --prefix=/usr/local/nginx --user=www --group=www --with-http_ssl_module --with-http_flv_module --with-http_stub_status_module --with-http_gzip_static_module --with-pcre
[root@web1 nginx-1.9.]#  make && make install

2.6、安装keeplived

（master和slave两台负载均衡机都要做）
[root@web1 nginx-1.9.]# cd /usr/local/src/
[root@web1 src]# tar -zvxf keepalived-1.3..tar.gz
[root@web1 src]# cd keepalived-1.3.
[root@web1 keepalived-1.3.]# ./configure
[root@web1 keepalived-1.3.]# make && make install
[root@web1 keepalived-1.3.]# cp /usr/local/src/keepalived-1.3./keepalived/etc/init.d/keepalived /etc/rc.d/init.d/
[root@web1 keepalived-1.3.]#  cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/
[root@web1 keepalived-1.3.]# mkdir /etc/keepalived
[root@web1 keepalived-1.3.]# cp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/
[root@web1 keepalived-1.3.]# cp /usr/local/sbin/keepalived /usr/sbin/
[root@web1 keepalived-1.3.]# echo "/usr/local/nginx/sbin/nginx" >> /etc/rc.local
[root@web1 keepalived-1.3.]# echo "/etc/init.d/keepalived start" >> /etc/rc.local

三、配置服务

3.1、关闭selinux

先关闭SElinux、配置防火墙 （master和slave两台负载均衡机都要做）
[root@web1 keepalived-1.3.]# cd /root/
[root@web1 ~]#sed -i 's/SELINUX=enforcing/SELinux=disabled/' /etc/selinux/config
[root@web1 ~]#grep SELINUX=disabled /etc/selinux/config
[root@web1 ~]#setenforce 

3.2、关闭防火墙

[root@web1 ~]# /etc/init.d/iptables  stop

3.3、配置nginx

　　master-和slave两台服务器的nginx的配置完全一样,主要是配置/usr/local/nginx/conf/nginx.conf的http，当然也可以配置vhost虚拟主机目录，然后配置vhost下的比如LB.conf文件。
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vhost/LB.conf下面配置upstream,然后在server或location中通过proxy_pass引用。

要实现前面规划的接入方式，LB.conf的配置如下（添加proxy_cache_path和proxy_temp_path这两行，表示打开nginx的缓存功能）：

[root@web1 ~]# vim /usr/local/nginx/conf/nginx.conf
user  www;
worker_processes  ;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;

events {
    worker_connections  ;
}

http {
    include       mime.types;
    default_type  application/octet-stream;
    charset utf-;
    ######
    ### set access log format
    #######
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  logs/access.log  main;
    #######
    ## http setting
    #######

    sendfile        on;
    #tcp_nopush     on;
    tcp_nopush     on;
    tcp_nodelay    on;
    keepalive_timeout  ;
    proxy_cache_path /var/www/cache levels=: keys_zone=mycache:20m max_size=2048m inactive=60m;
    proxy_temp_path /var/www/cache/tmp;

    fastcgi_connect_timeout ;
    fastcgi_send_timeout ;
    fastcgi_read_timeout ;
    fastcgi_buffer_size 256k;
    fastcgi_buffers  256k;
    fastcgi_busy_buffers_size 256k;
    fastcgi_temp_file_write_size 256k;
    fastcgi_intercept_errors on;

    #keepalive_timeout  ;
    #keepalive_timeout  ;

    #
    client_header_timeout 600s;
    client_body_timeout 600s;
   # client_max_body_size 50m;
    client_max_body_size 100m;               #允许客户端请求的最大单个文件字节数
    client_body_buffer_size 256k;            #缓冲区代理缓冲请求的最大字节数，可以理解为先保存到本地再传给用户

    #gzip  on;
    gzip_min_length  1k;
    gzip_buffers      16k;
    gzip_http_version 1.1;
    gzip_comp_level ;
    gzip_types       text/plain application/x-javascript text/css application/xml text/javascript application/x-httpd-php;
    gzip_vary on;

## includes vhosts
    include vhosts/*.conf;
}

# 创建相应的目录
[root@web1 ~]# mkdir -p /usr/local/nginx/conf/vhosts
[root@web1 ~]# mkdir -p /var/www/cache
[root@web1 ~]# ulimit 65535
[root@web2 ~]# vim /usr/local/nginx/conf/vhosts/LB.conf
upstream LB-WWW {
      ip_hash;
      server 172.16.12.223:80 max_fails=3 fail_timeout=30s;     #max_fails = 3 为允许失败的次数，默认值为1
      server 172.16.12.224:80 max_fails=3 fail_timeout=30s;     #fail_timeout = 30s 当max_fails次失败后，暂停将请求分发到该后端服务器的时间
      server 172.16.12.225:80 max_fails=3 fail_timeout=30s;
    }

upstream LB-OA {
      ip_hash;
      server 172.16.12.223:8080 max_fails=3 fail_timeout=30s;
      server 172.16.12.224:8080 max_fails=3 fail_timeout=30s;
}

  server {
      listen      80;
      server_name localhost;

      access_log  /usr/local/nginx/logs/dev-access.log main;
      error_log  /usr/local/nginx/logs/dev-error.log;

      location /svn {
         proxy_pass http://172.16.12.226/svn/;
         proxy_redirect off ;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header REMOTE-HOST $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_connect_timeout 300;             #跟后端服务器连接超时时间，发起握手等候响应时间
         proxy_send_timeout 300;                #后端服务器回传时间，就是在规定时间内后端服务器必须传完所有数据
         proxy_read_timeout 600;                #连接成功后等待后端服务器的响应时间，已经进入后端的排队之中等候处理
         proxy_buffer_size 256k;                #代理请求缓冲区,会保存用户的头信息以供nginx进行处理
         proxy_buffers 4 256k;                  #同上，告诉nginx保存单个用几个buffer最大用多少空间
         proxy_busy_buffers_size 256k;          #如果系统很忙时候可以申请最大的proxy_buffers
         proxy_temp_file_write_size 256k;       #proxy缓存临时文件的大小
         proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;
         proxy_max_temp_file_size 128m;
         proxy_cache mycache;
         proxy_cache_valid 200 302 60m;
         proxy_cache_valid 404 1m;
       }

      location /submin {
         proxy_pass http://172.16.12.226/submin/;
         proxy_redirect off ;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header REMOTE-HOST $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_connect_timeout 300;
         proxy_send_timeout 300;
         proxy_read_timeout 600;
         proxy_buffer_size 256k;
         proxy_buffers 4 256k;
         proxy_busy_buffers_size 256k;
         proxy_temp_file_write_size 256k;
         proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;
         proxy_max_temp_file_size 128m;
         proxy_cache mycache;
         proxy_cache_valid 200 302 60m;
         proxy_cache_valid 404 1m;
        }
    }

server {
     listen       80;
     server_name  localhost;

      access_log  /usr/local/nginx/logs/www-access.log main;
      error_log  /usr/local/nginx/logs/www-error.log;

     location / {
         proxy_pass http://LB-WWW;
         proxy_redirect off ;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header REMOTE-HOST $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_connect_timeout 300;
         proxy_send_timeout 300;
         proxy_read_timeout 600;
         proxy_buffer_size 256k;
         proxy_buffers 4 256k;
         proxy_busy_buffers_size 256k;
         proxy_temp_file_write_size 256k;
         proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;
         proxy_max_temp_file_size 128m;
         proxy_cache mycache;
         proxy_cache_valid 200 302 60m;
         proxy_cache_valid 404 1m;
        }
}

 server {
       listen       80;
       server_name  localhost;

      access_log  /usr/local/nginx/logs/oa-access.log main;
      error_log  /usr/local/nginx/logs/oa-error.log;

       location / {
         proxy_pass http://LB-OA;
         proxy_redirect off ;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header REMOTE-HOST $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_connect_timeout 300;
         proxy_send_timeout 300;
         proxy_read_timeout 600;
         proxy_buffer_size 256k;
         proxy_buffers 4 256k;
         proxy_busy_buffers_size 256k;
         proxy_temp_file_write_size 256k;
         proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;
         proxy_max_temp_file_size 128m;
         proxy_cache mycache;
         proxy_cache_valid 200 302 60m;
         proxy_cache_valid 404 1m;
        }
}

3.4、验证准备

3.4.1、在svn服务器上执行

cat >/usr/local/nginx/conf/vhosts/svn.conf <<EOF
server {
listen ;
server_name svn 172.16.12.225;

access_log /usr/local/nginx/logs/svn-access.log main;
error_log /usr/local/nginx/logs/svn-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}
EOF
[root@svn ~]# cat /usr/local/nginx/conf/vhosts/svn.conf
server {
listen ;
server_name svn 172.16.12.225;

access_log /usr/local/nginx/logs/svn-access.log main;
error_log /usr/local/nginx/logs/svn-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}
[root@svn ~]#
[root@svn ~]# mkdir -p /var/www/html
[root@svn ~]# mkdir -p /var/www/html/submin
[root@svn ~]# mkdir -p /var/www/html/svn
[root@svn ~]# cat /var/www/html/svn/index.html
this is the page of svn/172.16.12.225
[root@svn ~]#  cat /var/www/html/submin/index.html
this is the page of submin/172.16.12.225
[root@svn ~]# chown -R www.www /var/www/html/
[root@svn ~]# chmod -R  /var/www/html/
[root@svn ~]# cat  /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.12.223 web1
172.16.12.224 web2
172.16.12.225 svn
[root@svn ~]# tail -  /etc/rc.local
touch /var/lock/subsys/local
/etc/init.d/iptables stop
/usr/local/nginx/sbin/nginx
/etc/init.d/keepalived start

# 启动nginx
[root@svn ~]# /usr/local/nginx/sbin/nginx
# 访问网址
[root@svn local]# curl http://172.16.12.225/submin/
this is the page of submin/172.16.12.225
[root@svn local]# curl http://172.16.12.225/svn/
this is the page of svn/172.16.12.225

3.4.1、在web1上执行

[root@web1 ~]# curl http://172.16.12.225/submin/
this is the page of submin/172.16.12.225
[root@web1 ~]# curl http://172.16.12.225/svn/
this is the page of svn/172.16.12.225

cat >/usr/local/nginx/conf/vhosts/web.conf <<EOF
server {
listen ;
server_name web 172.16.12.223;

access_log /usr/local/nginx/logs/web-access.log main;
error_log /usr/local/nginx/logs/web-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}
EOF

[root@web1 ~]# cat /usr/local/nginx/conf/vhosts/web.conf
server {
listen ;
server_name web 172.16.12.223;

access_log /usr/local/nginx/logs/web-access.log main;
error_log /usr/local/nginx/logs/web-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}

[root@web1 ~]# mkdir -p /var/www/html
[root@web1 ~]# mkdir -p /var/www/html/web
[root@web1 ~]# cat  /var/www/html/web/index.html
this is the page of web/172.16.12.223
[root@web1 ~]# chown -R www.www /var/www/html/
[root@web1 ~]# chmod -R  /var/www/html/
[root@web1 ~]# cat  /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.12.223 web1
172.16.12.224 web2
172.16.12.225 svn
[root@web1 ~]# tail -  /etc/rc.local
touch /var/lock/subsys/local
/etc/init.d/iptables stop
/usr/local/nginx/sbin/nginx
/etc/init.d/keepalived start
[root@web1 ~]# /usr/local/nginx/sbin/nginx
[root@web1 ~]# curl http://172.16.12.223/web/
this is the page of web/172.16.12.223

2.4.2、在web2上执行

[root@web2 ~]# curl http://172.16.12.225/submin/
this is the page of submin/172.16.12.225
[root@web2 ~]# curl http://172.16.12.225/svn/
this is the page of svn/172.16.12.225

cat >/usr/local/nginx/conf/vhosts/web.conf <<EOF
server {
listen ;
server_name web 172.16.12.224;

access_log /usr/local/nginx/logs/web-access.log main;
error_log /usr/local/nginx/logs/web-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}
EOF

[root@web2 ~]# cat /usr/local/nginx/conf/vhosts/web.conf
server {
listen ;
server_name web 172.16.12.224;

access_log /usr/local/nginx/logs/web-access.log main;
error_log /usr/local/nginx/logs/web-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}
[root@web2 ~]#
[root@web2 ~]# mkdir -p /var/www/html
[root@web2 ~]# mkdir -p /var/www/html/web
[root@web2 ~]# cat /var/www/html/web/index.html
this is the page of web/172.16.12.224
[root@web2 ~]#  cat /var/www/html/web/index.html
this is the page of web/172.16.12.224
[root@web2 ~]# chown -R www.www /var/www/html/
[root@web2 ~]# chmod -R  /var/www/html/
[root@web2 ~]# cat  /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.12.223 web1
172.16.12.224 web2
172.16.12.225 svn
[root@web2 ~]# tail -  /etc/rc.local
touch /var/lock/subsys/local
/etc/init.d/iptables stop
/usr/local/nginx/sbin/nginx
/etc/init.d/keepalived start

# 启动nginx
[root@web2 ~]# /usr/local/nginx/sbin/nginx
# 访问网址
[root@web2 local]# curl http://172.16.12.224/web/
this is the page of web/172.16.12.224

2.4.3、浏览器测试

四、keeplived配置

4.1、web1上的操作

[root@web1 ~]#  cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@web1 ~]#  vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived     #全局定义

global_defs {
# notification_email {     #指定keepalived在发生事件时(比如切换)发送通知邮件的邮箱
# ops@wangshibo.cn   #设置报警邮件地址，可以设置多个，每行一个。 需开启本机的sendmail服务
# tech@wangshibo.cn
# }
#
# notification_email_from ops@wangshibo.cn   #keepalived在发生诸如切换操作时需要发送email通知地址
# smtp_server 127.0.0.1      #指定发送email的smtp服务器
# smtp_connect_timeout     #设置连接smtp server的超时时间
router_id master-node     #运行keepalived的机器的一个标识，通常可设为hostname。故障发生时，发邮件时显示在邮件主题中的信息。
}

vrrp_script chk_http_port {      #检测nginx服务是否在运行。有很多方式，比如进程，用脚本检测等等
    script "/opt/chk_nginx.sh"   #这里通过脚本监测
    interval                    #脚本执行间隔，每2s检测一次
    weight -                    #脚本结果导致的优先级变更，检测失败（脚本返回非0）则优先级 -
    fall                     #检测连续2次失败才算确定是真失败。会用weight减少优先级（-255之间）
    rise                     #检测1次成功就算成功。但不修改优先级
}

vrrp_instance VI_1 {    #keepalived在同一virtual_router_id中priority（-）最大的会成为master，也就是接管VIP，当priority最大的主机发生故障后次priority将会接管
    state MASTER    #指定keepalived的角色，MASTER表示此主机是主服务器，BACKUP表示此主机是备用服务器。注意这里的state指定instance(Initial)的初始状态，就是说在配置好后，这台服务器的初始状态就是这里指定的，但这里指定的不算，还是得要通过竞选通过优先级来确定。如果这里设置为MASTER，但如若他的优先级不及另外一台，那么这台在发送通告时，会发送自己的优先级，另外一台发现优先级不如自己的高，那么他会就回抢占为MASTER
    interface eth1          #指定HA监测网络的接口。实例绑定的网卡，因为在配置虚拟IP的时候必须是在已有的网卡上添加的
#    mcast_src_ip 103.110.98.14  # 发送多播数据包时的源IP地址，这里注意了，这里实际上就是在哪个地址上发送VRRP通告，这个非常重要，一定要选择稳定的网卡端口来发送，这里相当于heartbeat的心跳端口，如果没有设置那么就用默认的绑定的网卡的IP，也就是interface指定的IP地址
    virtual_router_id          #虚拟路由标识，这个标识是一个数字，同一个vrrp实例使用唯一的标识。即同一vrrp_instance下，MASTER和BACKUP必须是一致的
    priority                  #定义优先级，数字越大，优先级越高，在同一个vrrp_instance下，MASTER的优先级必须大于BACKUP的优先级
    advert_int                  #设定MASTER与BACKUP负载均衡器之间同步检查的时间间隔，单位是秒
    authentication {             #设置验证类型和密码。主从必须一样
        auth_type PASS           #设置vrrp验证类型，主要有PASS和AH两种
        auth_pass            #设置vrrp验证密码，在同一个vrrp_instance下，MASTER与BACKUP必须使用相同的密码才能正常通信
    }
    virtual_ipaddress {          #VRRP HA 虚拟地址 如果有多个VIP，继续换行填写
        172.16.12.226
    }

track_script {                      #执行监控的服务。注意这个设置不能紧挨着写在vrrp_script配置块的后面（实验中碰过的坑），否则nginx监控失效！！
   chk_http_port                    #引用VRRP脚本，即在 vrrp_script 部分指定的名字。定期运行它们来改变优先级，并最终引发主备切换。
}
}

4.2、web2上的操作

[root@web2 ~]#  cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@web2 ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived    

global_defs {
#  notification_email {
#  ops@wangshibo.cn
#  tech@wangshibo.cn
#  }
#
#  notification_email_from ops@wangshibo.cn
#  smtp_server 127.0.0.1
#  smtp_connect_timeout
router_id slave-node
}

vrrp_script chk_http_port {
    script "/opt/chk_nginx.sh"
    interval
    weight -
    fall
    rise
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth1
#    mcast_src_ip 103.110.98.24
    virtual_router_id
    priority
    advert_int
    authentication {
        auth_type PASS
        auth_pass
    }
    virtual_ipaddress {
        172.16.12.226
    }

track_script {
   chk_http_port
}

}

4.3、监控说明

　　让keepalived监控NginX的状态：
1）经过前面的配置，如果master主服务器的keepalived停止服务，slave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。
2）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。

注意：这里要提示一下keepalived.conf中vrrp_script配置区的script一般有2种写法：
1）通过脚本执行的返回结果，改变优先级，keepalived继续发送通告消息，backup比较优先级再决定。这是直接监控Nginx进程的方式。
2）脚本里面检测到异常，直接关闭keepalived进程，backup机器接收不到advertisement会抢占IP。这是检查NginX端口的方式。
上文script配置部分，"killall -0 nginx"属于第1种情况，"/opt/chk_nginx.sh" 属于第2种情况。个人更倾向于通过shell脚本判断，但有异常时exit 1，正常退出exit 0，然后keepalived根据动态调整的 vrrp_instance 优先级选举决定是否抢占VIP：
如果脚本执行结果为0，并且weight配置的值大于0，则优先级相应的增加
如果脚本执行结果非0，并且weight配置的值小于0，则优先级相应的减少
其他情况，原本配置的优先级不变，即配置文件中priority对应的值。

提示：
优先级不会不断的提高或者降低
可以编写多个检测脚本并为每个检测脚本设置不同的weight（在配置中列出就行）
不管提高优先级还是降低优先级，最终优先级的范围是在[1,254]，不会出现优先级小于等于0或者优先级大于等于255的情况
在MASTER节点的 vrrp_instance 中 配置 nopreempt ，当它异常恢复后，即使它 prio 更高也不会抢占，这样可以避免正常情况下做无谓的切换
以上可以做到利用脚本检测业务进程的状态，并动态调整优先级从而实现主备切换。

另外：在默认的keepalive.conf里面还有 virtual_server,real_server 这样的配置，我们这用不到，它是为lvs准备的。

如何尝试恢复服务
由于keepalived只检测本机和他机keepalived是否正常并实现VIP的漂移，而如果本机nginx出现故障不会则不会漂移VIP。
所以编写脚本来判断本机nginx是否正常，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，关闭keepalived，其他主机此时会接管VIP；

根据上述策略很容易写出监控脚本。此脚本必须在keepalived服务运行的前提下才有效！如果在keepalived服务先关闭的情况下，那么nginx服务关闭后就不能实现自启动了。
该脚本检测ngnix的运行状态，并在nginx进程不存在时尝试重新启动ngnix，如果启动失败则停止keepalived，准备让其它机器接管。

4.4、监控脚本

监控脚本如下（master和slave都要有这个监控脚本）：
[root@web1 ~]# cat  /opt/chk_nginx.sh
#!/bin/bash
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}" = "" ]; then
    /usr/local/nginx/sbin/nginx
    sleep
    counter=$(ps -C nginx --no-heading|wc -l)
    if [ "${counter}" = "" ]; then
        /etc/init.d/keepalived stop
    fi
fi
[root@web1 ~]#
[root@web1 ~]#  chmod  /opt/chk_nginx.sh
[root@web1 ~]# sh /opt/chk_nginx.sh

[root@web2 ~]# cat  /opt/chk_nginx.sh
#!/bin/bash
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}" = "" ]; then
    /usr/local/nginx/sbin/nginx
    sleep
    counter=$(ps -C nginx --no-heading|wc -l)
    if [ "${counter}" = "" ]; then
        /etc/init.d/keepalived stop
    fi
fi
[root@web2 ~]#
[root@web2 ~]#  chmod  /opt/chk_nginx.sh
[root@web2 ~]# sh /opt/chk_nginx.sh

4.5、需要考虑的问题

此架构需考虑的问题
1）master没挂，则master占有vip且nginx运行在master上
2）master挂了，则slave抢占vip且在slave上运行nginx服务
3）如果master上的nginx服务挂了，则nginx会自动重启，重启失败后会自动关闭keepalived，这样vip资源也会转移到slave上。
4）检测后端服务器的健康状态
5）master和slave两边都开启nginx服务，无论master还是slave，当其中的一个keepalived服务停止后，vip都会漂移到keepalived服务还在的节点上；
如果要想使nginx服务挂了，vip也漂移到另一个节点，则必须用脚本或者在配置文件里面用shell命令来控制。（nginx服务宕停后会自动启动，启动失败后会强制关闭keepalived，从而致使vip资源漂移到另一台机器上）

五、最后验证

最后验证（将配置的后端应用域名都解析到VIP地址上）：关闭主服务器上的keepalived或nginx，vip都会自动飘到从服务器上。

验证keepalived服务故障情况：

1）先后在master、slave服务器上启动nginx和keepalived，保证这两个服务都正常开启:

[root@web2 ~]# /usr/local/nginx/sbin/nginx  -s stop
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
[root@web2 ~]# /etc/init.d/keepalived  stop
Stopping keepalived:                                       [FAILED]
[root@web2 ~]# 

[root@web1 ~]# /usr/local/nginx/sbin/nginx  -s stop
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
[root@web1 ~]# /etc/init.d/keepalived  stop
Stopping keepalived:                                       [FAILED]
[root@web1 ~]#
[root@web1 ~]# /usr/local/nginx/sbin/nginx
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
[root@web1 ~]# /etc/init.d/keepalived  start
Starting keepalived:                                       [  OK  ]

2）在主服务器上查看是否已经绑定了虚拟IP：

[root@web1 ~]# ip add
: lo: <LOOPBACK,UP,LOWER_UP> mtu  qdisc noqueue state UNKNOWN
    link/loopback ::::: brd :::::
    inet 127.0.0.1/ scope host lo
    inet6 ::/ scope host
       valid_lft forever preferred_lft forever
: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::ca:: brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.223/ brd 10.0.2.255 scope global eth0
    inet 172.16.12.226/ scope global eth0
    inet6 fe80::a00:27ff:feca:/ scope link
       valid_lft forever preferred_lft forever
: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::b3:a9: brd ff:ff:ff:ff:ff:ff
    inet 172.16.12.223/ brd 172.16.12.255 scope global eth1
    inet6 fe80::a00:27ff:feb3:a936/ scope link
       valid_lft forever preferred_lft forever

[root@web2 ~]# /usr/local/nginx/sbin/nginx
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
nginx: [warn] conflicting server name "localhost" on 0.0.0.0:, ignored
[root@web2 ~]# /etc/init.d/keepalived  start
Starting keepalived:                                       [  OK  ]
[root@web2 ~]# ip add
: lo: <LOOPBACK,UP,LOWER_UP> mtu  qdisc noqueue state UNKNOWN
    link/loopback ::::: brd :::::
    inet 127.0.0.1/ scope host lo
    inet6 ::/ scope host
       valid_lft forever preferred_lft forever
: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::9a:0b: brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.224/ brd 10.0.2.255 scope global eth0
    inet6 fe80::a00:27ff:fe9a:b97/ scope link
       valid_lft forever preferred_lft forever
: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::::1a brd ff:ff:ff:ff:ff:ff
    inet 172.16.12.224/ brd 172.16.12.255 scope global eth1
    inet6 fe80::a00:27ff:fe63:261a/ scope link
       valid_lft forever preferred_lft forever
[root@web2 ~]# 

5.1、修改网站配置

[root@web1 ~]# cat  /usr/local/nginx/conf/vhosts/web.conf
server {
listen ;
server_name localhost 172.16.12.223 172.16.12.226;

access_log /usr/local/nginx/logs/web-access.log main;
error_log /usr/local/nginx/logs/web-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}
[root@web1 ~]# 

[root@web2 ~]# cat  /usr/local/nginx/conf/vhosts/web.conf
server {
listen ;
server_name localhost 172.16.12.224 172.16.12.226;

access_log /usr/local/nginx/logs/web-access.log main;
error_log /usr/local/nginx/logs/web-error.log;

location / {
root /var/www/html;
index index.html index.php index.htm;
}
}
[root@web2 ~]# 

5.2、访问验证

5.3、停止主服务器的keeplived服务

[root@web1 ~]# /etc/init.d/keepalived  stop
Stopping keepalived:                                       [  OK  ]
[root@web1 ~]#
[root@web1 ~]# tail -f  /var/log/messages
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_healthcheckers[]: Netlink reflector reports IP 172.16.12.226 added
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_vrrp[]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web1 Keepalived[]: Stopping
Dec  :: web1 Keepalived_vrrp[]: VRRP_Instance(VI_1) sent  priority
Dec  :: web1 Keepalived_vrrp[]: VRRP_Instance(VI_1) removing protocol VIPs.
Dec  :: web1 Keepalived_healthcheckers[]: Netlink reflector reports IP 172.16.12.226 removed
Dec  :: web1 Keepalived_healthcheckers[]: Stopped
Dec  :: web1 Keepalived_vrrp[]: Stopped
Dec  :: web1 Keepalived[]: Stopped Keepalived v1.3.2 (/,)

[root@web1 ~]# ip add
: lo: <LOOPBACK,UP,LOWER_UP> mtu  qdisc noqueue state UNKNOWN
    link/loopback ::::: brd :::::
    inet 127.0.0.1/ scope host lo
    inet6 ::/ scope host
       valid_lft forever preferred_lft forever
: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::ca:: brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.223/ brd 10.0.2.255 scope global eth0
    inet6 fe80::a00:27ff:feca:/ scope link
       valid_lft forever preferred_lft forever
: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::b3:a9: brd ff:ff:ff:ff:ff:ff
    inet 172.16.12.223/ brd 172.16.12.255 scope global eth1
    inet6 fe80::a00:27ff:feb3:a936/ scope link
       valid_lft forever preferred_lft forever
[root@web1 ~]# 

5.4、在web2查看切换情况

[root@web2 ~]# ip add
: lo: <LOOPBACK,UP,LOWER_UP> mtu  qdisc noqueue state UNKNOWN
    link/loopback ::::: brd :::::
    inet 127.0.0.1/ scope host lo
    inet6 ::/ scope host
       valid_lft forever preferred_lft forever
: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::9a:0b: brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.224/ brd 10.0.2.255 scope global eth0
    inet 172.16.12.226/ scope global eth0
    inet6 fe80::a00:27ff:fe9a:b97/ scope link
       valid_lft forever preferred_lft forever
: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP qlen
    link/ether :::::1a brd ff:ff:ff:ff:ff:ff
    inet 172.16.12.224/ brd 172.16.12.255 scope global eth1
    inet6 fe80::a00:27ff:fe63:261a/ scope link
       valid_lft forever preferred_lft forever
[root@web2 ~]# 

[root@web2 ~]# tail -f /var/log/messages
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_healthcheckers[]: Netlink reflector reports IP 172.16.12.226 added
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_vrrp[]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226
Dec  :: web2 Keepalived_vrrp[]: Sending gratuitous ARP on eth0 for 172.16.12.226

5.5、访问网页验证

切换前的网页：

切换后的网页：

说明已经切换完毕。