Nginx – How to alter the Last-Modified header on nginx

cachehttp-headersnginxweb-server

My server returns the following headers:

Cache-Control:no-cache
Connection:keep-alive
Date:Thu, 07 Jul 2011 10:41:57 GMT
Expires:Thu, 01 Jan 1970 00:00:01 GMT
Last-Modified:Thu, 07 Jul 2011 08:06:32 GMT
Server:nginx/0.8.46`

I want the content I'm serving not to be cached, so I'm looking for a way to return a Last-Modified header that contains the date-time when the request was originated. Something like now()…

Best Answer

"I want the content I'm serving not to be cached" : You can turn off If-Modified-Since request header checking with if_modified_since off; directive. if_modified_since doc

And about Last-Modified header: You can turn it off with add_header Last-Modified "";

Related Solutions

Why, sometimes the full content is returned unchanged, while If-Modified-Since is set

Can you use Firebug and paste the HTTP response headers. I have a feeling that even though in your code you are setting cache control to Public, Apache is overriding that because for Php File type you are setting Cache-Control to private.

One thing you can do it remove the cache settings for Dynamic Pages from Apache configuration. That should fix the problem because a Proxy doesn't cache a response without the correct headers.

EDIT

Hi Sam, Revisiting you question I found the solution to the problem. The following code snippet appears to be a problem. In the output of your Php the Last-Modified header always changes and when a browser sends a 304 If modified request it see a change and therefore re-requests that content.

header ("Last-Modified: " . gmdate("D, d M Y H:i:s", time() - 404800000)." GMT");

Unset Last-Modified and ETags from your content to speed up the website. This site provides some excellent tips too.
http://www.askapache.com/htaccess/apache-speed-last-modified.html

Is the Last-Modified HTTP header required for browser caching

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)?

Best Answer

Related Solutions

Why, sometimes the full content is returned unchanged, while If-Modified-Since is set

Is the Last-Modified HTTP header required for browser caching

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