Disable NGINX caching 304 Responses from Origin Server

Ryan Barclay ryan at rbftpnetworks.com
Tue Jul 25 07:24:30 UTC 2017

That's an interesting solution.  Would nginx still cache our other items 
as normal using this config?  We specify cache settings via 
Cache-Control and Expires headers sent from the origin server.  Also, we 
are using X-Accel-Expires for some pages which are sent from the origin 
server too.  This wouldn't affect any of our caching?  It would simply 
not cache any resources with 304 sent from the origin?

Another thought... would proxy_cache_valid override the Expires / 
Cache-Control headers sent along with the 304 response from the origin 
server?  Because with these 304 responses, the origin server sets a 3 
month expires.

Thank you for your help, it's much appreciated.

On 25/07/2017 02:35, Zhang Chao wrote:
> Hi!
> Have you used the proxy_cache_valid 
> <http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_valid>?
> Maybe you can add this directive to disable the 304 cache explicitly.
> |proxy_cache_valid 304 0;|
> On 24 July 2017 at 23:20:35, Ryan Barclay (ryan at rbftpnetworks.com 
> <mailto:ryan at rbftpnetworks.com>) wrote:
>> We have a pretty simple setup with NGINX sitting on the front and a
>> backend server (on a separate physical server) that provides the 
>> content.
>> Nginx then caches content based on the EXPIRES and Cache-Control headers
>> set by the origin server.
>> We noticed that NGINX was not issuing 304 headers to images that were
>> not in the local NGINX cache when the If-Modified-Since header was sent
>> by the client. Instead, it would issue a 200 with the full data file.
>> To fix this, we applied:
>> proxy_set_header If-Modified-Since $http_if_modified_since
>> So then the If-Modified-Since header was passed to the backend and of
>> course, it returned correctly with the 304 header - great.
>> But what we noticed was that NGINX would cache this 304 response and
>> deliver future responses as 304 to clients even without the
>> If-Modified-Since header.
>> How can we disable caching of 304 responses and fix this issue?
>> Thank you for your help, suggestions, and tips in advance.
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