Nginx proxy caching – how to check if it is working

I don't think that there is a way to explicitly invalidate cached items, but here is an example of how to do the rest. Update: As mentioned by Piotr in another answer, there is a cache purge module that you can use. You can also force a refresh of a cached item using nginx's proxy_cache_bypass - see Cherian's answer for more information.

In this configuration, items that aren't cached will be retrieved from example.net and stored. The cached versions will be served up to future clients until they are no longer valid (60 minutes).

Your Cache-Control and Expires HTTP headers will be honored, so if you want to explicitly set an expiration date, you can do that by setting the correct headers in whatever you are proxying to.

There are lots of parameters that you can tune - see the nginx Proxy module documentation for more information about all of this including details on the meaning of the different settings/parameters: http://nginx.org/r/proxy_cache_path

http {
  proxy_cache_path  /var/www/cache levels=1:2 keys_zone=my-cache:8m max_size=1000m inactive=600m;
  proxy_temp_path /var/www/cache/tmp; 


  server {
    location / {
      proxy_pass http://example.net;
      proxy_cache my-cache;
      proxy_cache_valid  200 302  60m;
      proxy_cache_valid  404      1m;
    }
  }
}

Be wary of reading random articles on the net (although Mark Nottingham's stuff is usually sensible). The definitive source should always by the RFCs. And according to RFC 2616 a browser should cache a document with an Expires: header where the timestamp is in the future, or where other valid caching instructions are provided provided that the document is not returned in response to a POST request.

It's perfectly valid to set a max-age without a last-modified - and the spec explicitly addresses that.

Certainly what you describe seems very unusual and implies that FF4.01 will never cache content - I would be amazed that it passed the QC checks with such a glaring omission. Can you provide details of the requests and responses proving this (e.g. with liveheaders)?