How to send proxy cache status to backend server?

[Makailol Charls]

Hi,

In my configuration I have caching layer of Nginx and a separate proxy
layer which works as reverse proxy to original upstream backend.

As discussed previously we can pass cache status from caching layer to
upstream but is there anything else which I can get from cache file (when
cache is expired) and pass to upstream?

I want to set some condition to my proxy layer to select original upstream
based on that.

Thanks,
Makailol


On Thu, Mar 27, 2014 at 6:19 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:

> Hello!
>
> On Thu, Mar 27, 2014 at 05:08:31PM +0530, Makailol Charls wrote:
>
> > Hi,
> >
> > Would it be possible to add this as new feature?
> >
> > Is there some other alternative ? Actually based on this header value I
> > want to select named based location.
>
> Response headers of expires cached responses are not read from a
> cache file.  If you really want this to happen, you may try to
> implement this, but I don't it's looks like a generally usable
> feature.  In most if not all cases it will be just a waste of
> resources.
>
> >
> >
> > Thanks,
> > Makailol
> >
> >
> > On Thu, Mar 27, 2014 at 5:02 PM, Maxim Dounin <mdounin at mdounin.ru>
> wrote:
> >
> > > Hello!
> > >
> > > On Thu, Mar 27, 2014 at 03:01:22PM +0530, Makailol Charls wrote:
> > >
> > > > Hi Maxim,
> > > >
> > > > Apart from passing cache status to backend, would it be possible to
> send
> > > > some other headers which are stored in cache?
> > > >
> > > > For example, If backed sets header "Foo : Bar" , which is stored in
> > > cache.
> > > > Now when cache is expired , request will be sent to backend. At that
> time
> > > > can we send the value of Foo header stored in cache to upstream
> backend?
> > > >
> > > > I tried to achieve this with below code but it could not work.
> > > > proxy_set_header Foo  $upstream_http_Foo;
> > > >
> > > > Would you suggest me how to achieve this or what am I doing wrong
> here.
> > >
> > > This is not something possible.
> > >
> > > >
> > > > Thanks,
> > > > Makailol
> > > >
> > > >
> > > >
> > > >
> > > > On Thu, Mar 20, 2014 at 6:56 PM, Maxim Dounin <mdounin at mdounin.ru>
> > > wrote:
> > > >
> > > > > Hello!
> > > > >
> > > > > On Thu, Mar 20, 2014 at 09:38:40AM +0530, Makailol Charls wrote:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > Is there some way to achieve this? I want to pass requests to
> backend
> > > > > based
> > > > > > on cache status condition.
> > > > >
> > > > > This is not something easily possible, as cache status is only
> > > > > known after we started processing proxy_pass and already know
> > > > > which backend will be used.  (Note that by default proxy_cache_key
> > > > > uses $proxy_host, which wouldn't be known otherwise.)
> > > > >
> > > > > If you want to check BYPASS as in your previous message, I would
> > > > > recommend checking relevant conditions from proxy_cache_bypass
> > > > > separately.  As a more generic though less effective aproach, an
> > > > > additional proxy layer may be used.
> > > > >
> > > > > --
> > > > > Maxim Dounin
> > > > > http://nginx.org/
> > > > >
> > > > > _______________________________________________
> > > > > nginx mailing list
> > > > > nginx at nginx.org
> > > > > http://mailman.nginx.org/mailman/listinfo/nginx
> > > > >
> > >
> > > > _______________________________________________
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> > > > nginx at nginx.org
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> > >
> > >
> > > --
> > > Maxim Dounin
> > > http://nginx.org/
> > >
> > > _______________________________________________
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> > > nginx at nginx.org
> > > http://mailman.nginx.org/mailman/listinfo/nginx
> > >
>
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>
> --
> Maxim Dounin
> http://nginx.org/
>
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