events {}
http {
    access_log off;
    error_log off;
    server {
        listen 80;
        location / {
            proxy_set_header Upgrade ${DOLLAR}http_upgrade;
            proxy_set_header Connection "upgrade";
            proxy_set_header Origin $MPP_ORIGIN;
            proxy_set_header User-Agent "thing";
            proxy_pass $MPP_URI;
        }
    }
}