Nginx+Keepalived实现站点高可用

说明：前端通过Nginx服务器把访问反代到后端的web服务器上，前端部署两台Nginx通过keepalived实现主备模式

一、软件安装

1、安装环境

CentOS Linux release 7.5.1804 (Core)

注意两台服务器时间同步，关闭firewalld和selinux

2、反代服务器安装

安装keepalived

# yum –y install keepalived

安装nginx

nginx包需要先安装epel源

# yum –y install epel-release

# yum –y install nginx

3、web服务器安装

本次实验和后端服务器关系不大，可以随意安装nginx或apache都行。

# yum –y install httpd

# systemctl start httpd

为方便测试，建立两个测试页面

web A：192.168.1.101

# echo AAAAAA > /var/www/html/index.html

web B：192.168.1.102

# echo BBBBB > /var/www/html/index.html

二、配置反代服务器nginx服务

1、注释掉nginx的默认server配置

# vim /etc/nginx/nginx.conf

#    server {
#        listen       80 default_server;
#        listen       [::]:80 default_server;
#        server_name  _;
#        root         /usr/share/nginx/html;

#        # Load configuration files for the default server block.
#        include /etc/nginx/default.d/*.conf;

#        location / {
#        }
#
#        error_page 404 /404.html;
#            location = /40x.html {
#        }

#        error_page 500 502 503 504 /50x.html;
#            location = /50x.html {
#        }

2、新建反代的配置

# vim /etc/nginx/conf.d/my.conf
upstream webservers {
    server 192.168.1.101:80;
    server 192.168.1.102:80;
}

server {
    listen 80;
    location / {
        proxy_pass http://webservers;
    }
}

3、开启nginx并测试

# systemctl start nginx

随便找一台测试机访问192.168.1.2 和192.168.1.3 反代是否正常运行

三、配置反代服务器keepalived服务

1、keepalived的基本配置

通过基本配置可以当反代服务器1宕机的时候可以跳转到反代服务器2上

反代1(192.168.1.2)上配置

# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id node1
}

vrrp_instance VI_1 {
    state MASTER
    interface ens32
    virtual_router_id 99
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.1.1
    }
}

反代2(192.168.1.3)上配置

# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id node1
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens32
    virtual_router_id 99
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.1.1
    }
}

启动服务测试

# systemctl start keepalived

问题说明

这种方法只有当反代服务器1上的keepalived服务挂掉，或者整个服务器宕机、断网等情况，导致keepalived无法进行心跳验证的情况下才会切换到备机。但是如果nginx服务挂了以后无法切换，那么可以采用下面的方案来实现。

2、keepalived进阶-监控nginx服务

反代1(192.168.1.2)上配置

# vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id node1
}
vrrp_script chk_nginx {
    script "/etc/keepalived/watch_nginx.sh"
    interval 1
    weight -20
}

vrrp_instance VI_1 {
    state MASTER
    interface ens32
    virtual_router_id 99
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.1.1
    }
    track_script {
        chk_nginx
    }
}

# vim /etc/keepalived/watch_nginx.sh
#!/bin/bash
killall -0 nginx &> /dev/null || exit 1

反代2(192.168.1.3)上配置

# vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id node1
}
vrrp_script chk_nginx {
    script "/etc/keepalived/watch_nginx.sh"
    interval 1
    weight -20
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens32
    virtual_router_id 99
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.1.1
    }
    track_script {
        chk_nginx
    }
}

# vim /etc/keepalived/watch_nginx.sh
#!/bin/bash
killall -0 nginx &> /dev/null || exit 1

重启服务测试

# systemctl restart keepalived

问题说明

nginx服务down了以后，直接切换到反代2上。可以通过notify脚本来使nginx服务进行重启。不过这种方法有弊有利，请根据实际情况斟酌。详细配置方法见下方案

3、keepalived进阶-nginx服务自动重启

反代1(192.168.1.2)上配置

# vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id node1
}
vrrp_script chk_nginx {
    script "/etc/keepalived/watch_nginx.sh"
    interval 1
    weight -20
}

vrrp_instance VI_1 {
    state MASTER
    interface ens32
    virtual_router_id 99
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.1.1
    }
    track_script {
        chk_nginx
    }
    notify_master "/etc/keepalived/notify.sh master"
    notify_backup "/etc/keepalived/notify.sh backup"
    notify_fault "/etc/keepalived/notify.sh fault"

}
#====================================

# vim /etc/keepalived/watch_nginx.sh
#!/bin/bash
killall -0 nginx &> /dev/null || exit 1
#====================================

# yum install -y mailx
# vim /etc/keepalived/notify.sh
#!/bin/bash
vip=192.168.1.1
contact='root@localhost'

notify() {
        mailsubject="`date '+%F %H:%M:%S'` HOST:`hostname` to be $1: $vip floating"
        mailbody="`date '+%F %H:%M:%S'` : vrrp transition, `hostname` changed to be $1"
        echo $mailbody | mail -s "$mailsubject" $contact
}

case "$1" in
        master)
                notify master
                exit 0
        ;;
        backup)
                notify backup
                systemctl restart nginx
                exit 0
        ;;
        fault)
                notify fault
                exit 0
        ;;
        *)
                echo 'Usage: `basename $0` {master|backup|fault}'
                exit 1
        ;;
esac

反代2(192.168.1.3)上配置

# vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id node1
}
vrrp_script chk_nginx {
    script "/etc/keepalived/watch_nginx.sh"
    interval 1
    weight -20
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens32
    virtual_router_id 99
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        192.168.1.1
    }
    track_script {
        chk_nginx
    }
    notify_master "/etc/keepalived/notify.sh master"
    notify_backup "/etc/keepalived/notify.sh backup"
    notify_fault "/etc/keepalived/notify.sh fault"

}
#====================================

# vim /etc/keepalived/watch_nginx.sh
#!/bin/bash
killall -0 nginx &> /dev/null || exit 1
#====================================

# yum install -y mailx
# vim /etc/keepalived/notify.sh
#!/bin/bash
vip=192.168.1.1
contact='root@localhost'

notify() {
        mailsubject="`date '+%F %H:%M:%S'` HOST:`hostname` to be $1: $vip floating"
        mailbody="`date '+%F %H:%M:%S'` : vrrp transition, `hostname` changed to be $1"
        echo $mailbody | mail -s "$mailsubject" $contact
}

case "$1" in
        master)
                notify master
                exit 0
        ;;
        backup)
                notify backup
                systemctl restart nginx
                exit 0
        ;;
        fault)
                notify fault
                exit 0
        ;;
        *)
                echo 'Usage: `basename $0` {master|backup|fault}'
                exit 1
        ;;
esac

重启服务测试

# systemctl restart keepalived