nginx+keepalived高可用（keepalived抢占

nginx single ip
keepalived源码：https://github.com/acassen/keepalived
nginx源码：https://github.com/nginx/nginx
环境：10.18.1.185（主） 10.18.1.183（备）
1.安装nginx + keep

sudo apt install nginx
sudo apt install keepalived

2.修改配置文件

sudo vi /etc/nginx/nginx.conf

配置文件改为以下内容，其中root代表html文件位置:

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
    worker_connections  1024;
}
http {
    include            mime.types;
    default_type       application/octet-stream;
    sendfile           on;
    keepalive_timeout  65;
    server {
        listen       80;
        server_name  localhost;
        location / {
            root   /var/www/html;
            index  index.html index.htm;
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

修改nginx183和185的返回：
/var/www/html/index.html的内容修改为对应的ip

sudo echo "185"  /var/www/html/index.html

3.修改keepalived的配置信息

sudo vi /etc/keepalived/keepalived.conf

主185的如下：

global_defs {
  router_id nginx_lb01
}

vrrp_script check_ng
{
   script "/etc/keepalived/script/check_nginx.sh"
   interval 1
}

vrrp_instance VI_1 {
    virtual_router_id 51
    state MASTER
    priority 101
    advert_int 1
    interface ens3
    authentication {
      auth_type PASS
      auth_pass 1111
    }
    virtual_ipaddress {
      10.18.1.195
    }
    unicast_src_ip 10.18.1.185
    unicast_peer {
        10.18.1.183
    }
    track_script {
      check_ng
    }
}

备183的如下：

global_defs {
  router_id nginx_lb02
}

vrrp_instance VI_1 {
    virtual_router_id 51
    state BACKUP
    priority 100
    advert_int 1
    interface ens3
    authentication {
      auth_type PASS
      auth_pass 1111
    }
    virtual_ipaddress {
      10.18.1.195
    }
    unicast_src_ip 10.18.1.183
    unicast_peer {
        10.18.1.185
    }
}

主185还需要nginx检测脚本，当nginx挂掉时，自动关闭keepalived:

sudo  mkdir /etc/keepalived/script

4.改变mysql目录权限

sudo chown -R mysql.mysql /usr/local/mysql/
sudo vi  /etc/keepalived/script/check_nginx.sh

脚本如下：

#!/bin/bash
# 
# Define variables 
RETVAL=0
NginxStats=$(netstat -lntup|grep ":80 "|grep -v grep|wc -l)

## $NginxStats = 0 and stop keepalived 
if [ "$NginxStats" -eq 0 ];then
   service keepalived stop
fi

5.重启nginx和keepalived

sudo service nginx restart (或sudo service nginx reload )
sudo service keepalived restart

看到如下输出：

● keepalived.service - Keepalive Daemon (LVS and VRRP)
   Loaded: loaded (/lib/systemd/system/keepalived.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2023-02-27 16:45:57 CST; 4s ago
  Process: 16369 ExecStart=/usr/sbin/keepalived $DAEMON_ARGS (code=exited, status=0/SUCCESS)
 Main PID: 16371 (keepalived)
    Tasks: 3 (limit: 4915)
   CGroup: /system.slice/keepalived.service
           ├─16371 /usr/sbin/keepalived
           ├─16375 /usr/sbin/keepalived
           └─16377 /usr/sbin/keepalived

2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: Registering Kernel netlink command channel
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: Registering gratuitous ARP shared channel
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: Opening file '/etc/keepalived/keepalived.conf'.
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: WARNING - default user 'keepalived_script' for script execution does not exist - please create.
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: Unsafe permissions found for script '/etc/keepalived/script/check_nginx.sh'.
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: SECURITY VIOLATION - scripts are being executed but script_security not enabled. There are insecure scripts.
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: Using LinkWatch kernel netlink reflector...
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: VRRP_Script(check_ng) succeeded
2月 27 16:45:57 sder_plt_185 Keepalived_vrrp[16377]: VRRP_Instance(VI_1) Transition to MASTER STATE
2月 27 16:45:58 sder_plt_185 Keepalived_vrrp[16377]: VRRP_Instance(VI_1) Entering MASTER STATE

输出如下：

● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2023-02-27 16:45:50 CST; 40s ago
     Docs: man:nginx(8)
  Process: 16017 ExecStop=/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid (code=exited, status=0/SUCCESS)
  Process: 16286 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
  Process: 16278 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
 Main PID: 16288 (nginx)
    Tasks: 33 (limit: 4915)
   CGroup: /system.slice/nginx.service
           ├─16288 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
           ├─16290 nginx: worker process
           ├─16292 nginx: worker process
           ├─16293 nginx: worker process
           ├─16294 nginx: worker process
           ├─16295 nginx: worker process
           ├─16298 nginx: worker process
           ├─16299 nginx: worker process
           ├─16300 nginx: worker process
           ├─16301 nginx: worker process
           ├─16302 nginx: worker process
           ├─16303 nginx: worker process

6.测试185nginx挂掉，183启用
先找一台其它机器：

curl 10.18.1.195

显示如下：

185

关闭185主的nginx服务：
sudo service nginx stop
再次执行，结果如下：

183

看到185的keepalived挂掉，inactive (dead)