proxy caching

[Lukas Tribus]

Hi,

give varnish [1] a look, its probably better suited for such a scenario.


[1] http://www.varnish-cache.org/



> Date: Sun, 8 May 2011 03:29:31 +0400
> From: mdounin at mdounin.ru
> To: nginx at nginx.org
> Subject: Re: proxy caching
> 
> Hello!
> 
> On Sat, May 07, 2011 at 08:49:43AM -0400, bluescreen303 wrote:
> 
> > Hi all,
> > 
> > I would like to use nginx to cache some responses from my backends.
> > There are basically 2 types of responses I would like to cache.
> > 
> > - public images that never expire
> > - private content
> > 
> > The first one was easy, got that working already. Since my application
> > uses timestamps in the html when referring to images, changes to them
> > will be instantly picked up.
> > 
> > The second one is way harder.
> > Responses can become quite large (1 upto 10Mb).
> > My backend application is putting etags on the responses so it can
> > return 304s if nothing changed.
> > Also, it puts a 5min max-age cache-control on it,
> > Lastly, responses are marked private, because they are behind http basic
> > authentication (handled by the backend app).
> > 
> > What I would like nginx to do is the following:
> > It should store the first response for a certain url, using the current
> > http auth in the key (so it won't accidentally become publicly
> > available).
> > If a second request comes in for the same url with the same http auth
> > within 5 minutes: serve from cache.
> > If a second request comes in for the same url with the same http auth
> > _after_ 5 mintutes: ask backend using the if-not-modified header.
> > - if modified, store the new response.
> > - if 304 not modified, respond from cache, update cache to be valid for
> > 5 minutes again.
> > If a request comes in for the same url but with other http auth: ignore
> > cache and ask backend.
> > 
> > The http auth stuff seems solvable by using the http auth in the
> > cache_key.
> > The other 2 things I would like to solve are:
> > 
> > - I can't find clear info about nginx's handling of etag and
> > if-not-modified. Will it work as described above out-of-the-box?
> > It's especially important that nginx uses if-not-modified when querying
> > the backend, even if the client request itself didn't contain it.
> > Ofcourse if the client request did include it, it should receive a nice
> > 304 too.
> 
> Right now nginx can't use conditional requests to refresh cache.
> 
> > - The backend sends Cache-Control: private for these responses. I would
> > like nginx to cache them though.
> > Ignoring the Cache-Control header doesn't seem to work (because without
> > cache-control at all, caching seems disabled)
> > Another option might be to have the backend set cache-control to public
> > and have nginx set it back to private, but that sounds a bit hacky.
> 
> Solution is to ignore Cache-Control header and enable caching 
> explicitly with proxy_cache_valid directive.
> 
> Maxim Dounin
> 
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