Last-Modified, IMS, 304 and ESI includes

Per Buer perbu at
Fri Oct 26 09:15:14 CEST 2012

Hi Hughes.

On Thu, Oct 25, 2012 at 8:49 PM, Hugues Alary <hugues.alary at>wrote:

> Hi there,
> I've been reading a lot about the Last-Modified header, IMS, 304 responses
> and ESI, on various websites and mostly on the Varnish trac because I'm
> trying to solve the following problem:
> All the pages on my website contain ESI includes. I'd like the pages to
> have their Last-Modified header set to the Last-Modified of
> the youngest ESI include contained in the page.

This is well known weakness, I'm afraid.

> All the documentation I read seem to indicate that it has been more or
> less on the roadmap for the last few years, I even saw some patches
> floating around, but all that stuff seems pretty old and I'm using Varnish
> 3.0.2 and could even use 3.0.3.
> Is there any way to achieve that? Does the experimental-IMS branch solves
> this "problem"? If yes, is it too experimental for production use?

Currently I don't know any reliable way of doing it. The IMS branch is
based of trunk code so whether it is stable enough is dependent on your
usage. Also, I don't know if it actually addresses the ESI/IMS issue.

I have the feeling that it is not possible at the moment, but I'd really
> like to have this feature as it would fairly improve the performances of my
> website.

It would have to implemented first.

 <> *Per Buer*
Varnish Software
Phone: +47 958 39 117 | Skype: per.buer
We Make Websites Fly!
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