修改如下试试：
服务器 A
server {
listen 9090;
server_name xxx.xxx.com;
location / {
proxy_redirect off;
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass http://xxx:8080;
}

}

服务器 B
listen 80 ;

server_name xxx.xxx.com;

location / {
proxy_redirect off;
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Port $server_port;
proxy_pass http://xxx.xxx.com:9090;
}


本机绑定 host 到服务器 B，访问 xxx.xxx.com ，可以的话，改 DNS。