On Sun, Jun 5, 2011 at 7:32 AM, Ben Noordhuis <i...@bnoordhuis.nl> wrote:
> On Sun, Jun 5, 2011 at 02:15, Joshua Marantz <jmara...@google.com> wrote: > > On Sat, Jun 4, 2011 at 7:58 PM, Ben Noordhuis <i...@bnoordhuis.nl> > wrote: > >> Some popular OSS packages depend on Vary: User-Agent to make > >> downstream proxies (reverse or forward) do the right thing. > > > > I'm pretty interested in deconstructing this further. Can you be more > > specific? Which OSS packages? Under what scenario would a proxy do the > > wrong thing in the absence of Vary:User-Agent (other than, obviously, > when > > the content actually varies based on user-agent)? > > From first-hand experience (because I broke it): Magento, a popular > PHP e-commerce framework. Magento (or one of its plug-ins) generates > browser-tailored HTML and sets the Vary header to ensure that > downstream proxies send the right HTML to the right client. If you > remove or ignore the header, the layout of your site breaks. > This is a case where the content varies based on user-agent. The recommendation on the mod_deflate doc page is add vary:user-agent for any non-image. Can you think of a case where the absence of a vary:user-agent header causes broken behavior when the content doesn't vary? I'm not objecting to setting vary:user-agent when content varies: that's what it's for. I'm objecting to setting vary:user-agent when content does *not* vary. The mod_deflate documentation unambiguously recommends setting vary:user-agent, and my feeling is that this is to work around a bug that exists only in IE5 or pre-2007 patch of IE6. -Josh
