# Nginx http proxy caching **URL:** \ **Category:** NGINX\ **Created:** [January 19, 2010, 6:54am UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848 "2010-01-19T06:54:25Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [January 19, 2010, 6:54am UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/1 "2010-01-19T06:54:25Z")
Hi, Is there developer documentation on how http caching works in nginx? I’m seeing weird caching behavior where it’s caching responses with Cache-Control: private headers. Does nginx obey all caching headers correctly? Also, is there a way to override the caching headers for certain requests only? As I’ve asked in another thread, I’m also trying to understand how I can enable/disable caching per request based on a cookie or a header set by upstream server. I’ve not found an answer to it yet. Any help is much appreciated. Thanks, ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 10, 2010, 9:16pm UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/2 "2010-05-10T21:16:04Z")
On Mon, May 10, 2010 at 03:02:09PM -0400, Jim Ursetto wrote: > nginx to not use the proxy cache while still allowing > the browser to cache (for example, > `Cache-control: max-age=3600, private`). You can only > disable the proxy cache in the configuration file based > on the current Location. I don’t really understand this > behavior; I think private should be honored. You are right, “private” should be ignored. However, you may say nginx “X-Accel-Expires: 0” to not cache such responses. You may say different cache times for nginx and browsers/transit proxies: X-Accel-Expires: 500 Cache-Control: max-age=100 – Igor S. > **[Igor Sysoev](http://sysoev.ru/en/)** ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 10, 2010, 9:03pm UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/3 "2010-05-10T21:03:11Z")
## Vinay Y S Wrote: > Hi, > Is there developer documentation on how http > caching works in nginx? I’m > seeing weird caching behavior where it’s caching > responses with Cache-Control: private headers. nginx completely ignores the `private` keyword and will cache your document regardless. > As I’ve asked in another thread, I’m also trying > to understand how I can > enable/disable caching per request based on a > cookie or a header set by > upstream server. You can send `Cache-control: max-age=0` or `Cache-control: no-cache` to disable nginx proxy cache. Note that because `private` is ignored, you cannot tell nginx to not use the proxy cache while still allowing the browser to cache (for example, `Cache-control: max-age=3600, private`). You can only disable the proxy cache in the configuration file based on the current Location. I don’t really understand this behavior; I think private should be honored. Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,42865,85008#msg-85008](http://forum.nginx.org/read.php?2,42865,85008#msg-85008) ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 10, 2010, 9:44pm UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/4 "2010-05-10T21:44:44Z")
Igor S. Wrote: > However, you may say nginx “X-Accel-Expires: 0” to > not cache such > responses. You may say different cache times for > nginx and > browsers/transit proxies: Oh, thank you. That is very useful. Jim Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,42865,85035#msg-85035](http://forum.nginx.org/read.php?2,42865,85035#msg-85035) ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 10, 2010, 11:55pm UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/5 "2010-05-10T23:55:53Z")
On Mon, May 10, 2010 at 2:15 PM, Igor S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > nginx completely ignores the `private` keyword and > > responses. You may say different cache times for nginx and > browsers/transit proxies: > > X-Accel-Expires: 500 > Cache-Control: max-age=100 Ach… is this really true? It is a fundamental HTTP spec violation to ignore “private” cache-control directives in a proxy (even a reverse proxy I would think). It says in the documentation that it will obey cache-control headers here: > **[GitHub - nginxinc/nginx-wiki: ARCHIVED -- Source for the now archived NGINX Wiki...](https://github.com/nginxinc/nginx-wiki)** > > ARCHIVED -- Source for the now archived NGINX Wiki section of https://www.nginx.com Is the documentation incorrect? Are “private”, “no-transform”, ,“proxy-revalidate”, and other such headers are ignored by nginx? I just introduced caching into our QA environment for a whole site, expecting sane behavior on the part of nginx. I guess I better do some multi-user testing or roll it back out of caution… – RPM ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 10, 2010, 11:41pm UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/6 "2010-05-10T23:41:15Z")
Igor S. Wrote: > However, you may say nginx “X-Accel-Expires: 0” to > not cache such > responses. You may say different cache times for > nginx and > browsers/transit proxies: Oh, thank you. It didn’t occur to me to use X-Accel-Expires. Jim Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,42865,85039#msg-85039](http://forum.nginx.org/read.php?2,42865,85039#msg-85039) ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 11, 2010, 3:06am UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/7 "2010-05-11T03:06:08Z")
Hello! On Mon, May 10, 2010 at 04:55:03PM -0500, Ryan M. wrote: > > > `Cache-control: no-cache` to disable nginx proxy cache. > > > However, you may say nginx “X-Accel-Expires: 0” to not cache such > > > responses. You may say different cache times for nginx and > > > browsers/transit proxies: > > > > X-Accel-Expires: 500 > > Cache-Control: max-age=100 > > Ach… is this really true? It is a fundamental HTTP spec violation to > ignore “private” cache-control directives in a proxy (even a reverse > proxy I would think). There are lots of situations where you have to cache private data on reverse proxy. And you can do this safely by providing appropriate proxy\_cache\_key. I agree that private data shouldn’t be cached by default, but I don’t see any “fundamental violation” here. In HTTP terms nginx is origin server, and it’s up to it’s admin to configure it to do whatever he want. > It says in the documentation that it will obey cache-control headers here: > [GitHub - nginxinc/nginx-wiki: ARCHIVED -- Source for the now archived NGINX Wiki section of https://www.nginx.com · GitHub](http://wiki.nginx.org/NginxHttpProxyModule#proxy_cache) Wiki isn’t documentation, it’s user-contributed content. > Is the documentation incorrect? Are “private”, “no-transform”, > ,“proxy-revalidate”, and other such headers are ignored by nginx? I > just introduced caching into our QA environment for a whole site, > expecting sane behavior on the part of nginx. I guess I better do some > multi-user testing or roll it back out of caution… The only cache-control directives currently honored are “no-cache” and “max-age=”. And yes, using proxy\_cache on some arbitrary backend which wasn’t designed to work with nginx isn’t really good idea (at least right now). Maxim D. ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 14, 2010, 3:11pm UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/8 "2010-05-14T15:11:38Z")
2010/5/10 Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > There are lots of situations where you have to cache private data > on reverse proxy. Â And you can do this safely by providing > appropriate proxy\_cache\_key. Only if you’re able to create separate nginx locations or different proxy\_cache\_key definitions for public items versus potentially private dynamic pages based on URI alone. This isn’t possible with quite a few content management and collaboration systems, especially those which dynamically return images or other content from a database. In such systems, the URLs are usually something like [http://myserver.com/content/id354325435ed434](http://myserver.com/content/id354325435ed434), with Cache-Control and Content-Type headers being set dynamically. You can’t add a cookie or anything else to the proxy\_cache\_key without giving up caching of public items. > I agree that private data shouldn’t be cached by default, but I > don’t see any “fundamental violation” here. Â In HTTP terms nginx > is origin server, and it’s up to it’s admin to configure it to do > whatever he want. Nginx with the HTTP proxy module certainly doesn’t meet the definition of “origin” in RFC 2616. I agree the flexibility to go against the specification is desirable, but as you say, the default behavior should conform to the RFC. > Wiki isn’t documentation, it’s user-contributed content. Is the Russian version at [nginx: документация](http://sysoev.ru/nginx/docs/) the only official documentation? I wish I understood Russian and was able to help keep an up-to-date English version. Google translate does a decent job, but with technical content that’s not always good enough. It would probably be best to distribute revision-controlled HTML documentation which correspond to source code releases. I am willing to help the project in this area. > The only cache-control directives currently honored are “no-cache” > and “max-age=”. ## I started looking at the source, but was thoroughly confused because there are so few comments. It seems that a simple patch to ngx\_http\_upstream.c which sets “u-\>cacheable = 0;” if a “private” keyword (or for that matter other Cache-Control headers than nginx does not yet understand) wold be a workable first step… RPM ---
**Author:** ![vys](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/4bbf92/32.png) [@vys](https://www.ruby-forum.com/u/vys)\ **Post date:** [May 14, 2010, 4:30pm UTC](https://www.ruby-forum.com/t/nginx-http-proxy-caching/181848/9 "2010-05-14T16:30:40Z")
2010/5/10 Maxim D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > Wiki isn’t documentation, it’s user-contributed content. ## I updated the English Wiki at [GitHub - nginxinc/nginx-wiki: ARCHIVED -- Source for the now archived NGINX Wiki section of https://www.nginx.com · GitHub](http://wiki.nginx.org/NginxHttpProxyModule#proxy_cache) to provide a better description of the current behavior. RPM