Strange different behavior

Kristian Lyngstol kristian at
Thu Jan 14 22:50:25 CET 2010

On Wed, Jan 13, 2010 at 06:45:26PM +0100, Bernardf FRIT wrote:
> Hi,
> I'm facing a pretty strange issue. URLs not supposed to be cached are in
> cache when
> requested by firefox but not by lwp.


> Vary: Accept-Encoding,User-Agent

This is why.

Vary: means "this page will look different depending on the following
client headers".

Your backend is telling Varnish to expect different variants of the page
depending on what Accept-Encoding AND User-Agent header the client
provides. Accept-Encoding is normal and sane (ie: if one client supports
gzip and an other does not, one client will get a compressed variant of the
page and the other client the uncompressed one).

Vary on User-Agent is generally bad, and you should Just Fix That [tm].

Due to Vary: Accept-Encoding, lwp-request and Firefox will still get
different variants, but you can supply the Accept-Encoding header to
lwp-request, but if you want the content, you'll need to pipe it through
gunzip (headers are still readable).

Kristian Lyngstøl
Redpill Linpro AS
Mob: +47 99014497
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