nginx configuration to forward requests to apache if there's no nginx server block handling the specific request

apache.conf

server {
	listen 8999 default_server;
	server_name _;

	location / {
		# return 418; #teacup for test
		proxy_set_header X-Real-IP  $remote_addr;
		proxy_set_header X-Forwarded-For $remote_addr;
		proxy_set_header Host $host;
		proxy_pass http://127.0.0.1:8080;
	}

	location ~ /\. {
		deny all;
		access_log off;
		log_not_found off;
	}
}