nginx caching thumbor webp/jpg

gistfile1.nginxconf

proxy_cache_path /tmp/nginx levels=1:2 keys_zone=my_zone:10m inactive=60m;
proxy_cache_key "$host$request_uri-$format";

server {
  listen 999;
  server_name _;

  set $format jpg;
  if ( $http_accept ~* 'webp' ) {
    set $format webp;
  }

  location / {
    proxy_cache my_zone;
    proxy_pass http://localhost:9000;
  }
}