Re: [PATCH 1/1] snapshot::web Fix internal redirects to farm
On Wed, 2024-11-20 at 16:47 +0100, Philipp Kern wrote:
> On 11/20/24 3:48 PM, MOESSBAUER, Felix wrote:
> > I had to re-learn Apache rules again as I'm also an Nginx user.
> > Felt a bit like traveling 10 years into the past.
>
> Same. :)
>
> > > I.e. we could do literally what you suggested but key it off the
> > > User-Agent and set the Vary header?
> >
> > Technically we can, but this significantly reduces the caching on
> > Fastly, as we can't encode "cache for all, except if this user-
> > agent".
> >
> > I have no idea how to properly resolve this. If someone more
> > familiar
> > with HTTP caching is reading this, please speak up.
>
> We basically own the whole stack (and Fastly allows ~arbitrary VCL).
> I'd
> be open to something like this:
Okay... That's good.
>
> Fastly matches on UA and inserts a header "X-Download-Directly: yes"
> if
> the UA is apt-cacher-ng, otherwise it will send "X-Download-Directly:
> no". We sent a "Vary: X-Download-Directly" back.
If you take care of the Fastly part, I'll update the local varnish VCL
rules to handle the X-Download-Directly (I'll send the patch to this ML
by EO today).
>
> The general guidance from Fastly[1] is to narrow the Vary header
> content
> down to a few cache keys. That'd be two. I think that'd be fine, as
> it'd
> only apply to files fetched by apt-cacher-ng where the caching would
> then be worse. But that's better than being broken. And we could
> still
> patch apt-cacher-ng and fix it for the future - although then it'd be
> cool if there would be a sane way to match on the UA to identify
> fixed
> versions. Like "apt-cacher-ng/version allow-redirects". =)
The patch is already available, it just needs a proposed update upload:
https://lists.debian.org/debian-snapshot/2024/10/msg00010.html
Anyways, that's on your end. My rules will only care about the X-
Download-Directly header.
Best regards,
Felix Moessbauer
>
> Kind regards and thanks for the brainstorming and keeping me honest
> Philipp Kern
>
> [1] https://www.fastly.com/blog/best-practices-using-vary-header
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