Varnish could build an Etag based on all collected Etags from the backend

Jordi Llach jllach at
Wed Nov 30 15:40:03 CET 2016

>From my ignorance sounds strange as the final response is a composition of
multiple sub-requests, which in turn are cached individually.
Thanks for the feedback

2016-11-30 10:53 GMT+01:00 Dridi Boukelmoune <dridi at>:

> On Wed, Nov 30, 2016 at 10:22 AM, Jordi Llach <jllach at>
> wrote:
> > When using Varnish in conjunction with ESis no one but Varnish could
> build a
> > global Etag that really summarizes the response send to the client.
> >
> > I am wondering if Varnish could build a global Etag based on all Etags
> > received from the backend.
> > I understand that creating this Etag from multiple chunks(ESIs) is cpu
> > intensive and thus I am wondering if Varnish could build this Etag based
> on
> > all ESI Etags received, instead of doing it from the body/html in itself
> Short answer is no, the game is over before you get to the response
> headers of ESI sub-requests.
> Dridi
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