Pull CDN using NGINX. domain.tld.cdn.example.com/uri will be fetched from domain.tld/uri and stored in /cdn/domain.tld/uri

nginx_pull_cdn

server {
    listen       80;
    server_name  *.cdn.example.com;

    set $origin_host 'nothing';

    if ( $host ~* ([^.]+\.[^.]+)\.cdn\.example\.com$ ) {
        set $origin_host $1;
    }

    access_log  /var/log/nginx/cdn.example.com.access.log  main;

    location / {
        root               /backup/cdn/$origin_host;
        error_page         404 = @fetch;
    }

    location @fetch {
        internal;

        proxy_pass         http://$origin_host;
        proxy_store        on;
        proxy_store_access user:rw group:rw all:r;
        proxy_temp_path    /cdn/temp;

        root               /cdn/$origin_host;
    }
}