nginx dynamic caching using proxy_store with reverse-proxy fallback

nginx-dynamic-cache.conf

# servers to proxy to
upstream servers {
       server 10.0.0.1;
       server 10.0.0.2;
}

server {
       listen 80;
       server_name www.domain.com;
       server_name www2.domain.com
       
       # this proxy_method flag for logging will be helpful 
       # in determining if object is passed, cached or stored

       set $proxy_method STORE; 
       set $store_extra '';

       # store dynamic content as physical files
       # appended with a .json extension
       
       location ~ /GetJSON {
               root                    /var/tmp/nginx/json;
               expires                 max;
               try_files               $request_uri.json @fetch_json ;
       }

       location @fetch_json {
               internal;
               proxy_pass              http://servers$request_uri;
               proxy_store             /var/tmp/nginx/json${request_uri}.json;
               proxy_store_access      user:rw group:rw all:r;
               set                     $proxy_method PASS;

       }

       # any other static content will be handled by nginx
       # reverse proxy and caching

       location / {
               proxy_ignore_headers    X-Accel-Expires Expires Cache-Control Set-Cookie;
               proxy_cache             MYCACHE;
               expires                 max;
               proxy_cache_use_stale   error;
               proxy_cache_valid       any 30d;
               proxy_pass              http://servers$request_uri;
               add_header              X-NGINX-Cache $upstream_cache_status;
               set                     $proxy_method CACHE;
       }


      # this custom logging will show a 'HIT' or a 'MISS' tag
      # per content

       log_format  up_head  '[$time_local] "$request" '
                     '$status $body_bytes_sent "$http_referer"'
                     '"$http_x_forwarded_for" "$upstream_cache_status"'
                       '"$proxy_method"'

       access_log /var/log/nginx/cache.log up_head;
}