It was with some reluctance that I brought this up. It occurs to me that this idea propagates the sort of spec violations that led to this issue (inappropriate user of Vary:User-Agent) in the first place. However, I'm trying to figure out how to improve compliance to support legitimate uses of Vary:User-Agent without causing mod_pagespeed to become significantly less ineffective across a broad range of sites.
We have found that putting complaints in Apache logs mostly causes disks to fill and servers to crash -- although that does get it noticed :). The problem, put another way, is that mod_pagespeed cannot distinguish legitimate uses of Vary:User-Agent, so it really has no business complaining in logs. Complaining in docs is fine; but some existing mod_pagespeed users that simply type "sudo yum update" will later notice a performance-drop and may not consult the docs to figure out why. I'm also trying to grok the first response from Eric: It's because of the other (dated) canned exceptions that set/unset no-gzip/gzip-only-text/html based on the User-Agent, to second-guess browsers that send AE:gzip but can't properly deal with it. Going backwards: which browsers send AE:gzip but can't properly deal with it? Does IE6 have that issue or is it only true of IE5? I know that IE6 has had issues with compression in the past but they appear to be addressed by patches issued by Microsoft four and a half years ago: http://support.microsoft.com/default.aspx?scid=kb;en-us;Q312496. Moreover IE6 is shrinking in market share<http://arstechnica.com/web/news/2011/05/web-browser-market-share-upgrade-analysis.ars>(~ 10%) and IE5 does not appear in the pie-chart at all. And I still don't understand how that relates to Vary:User-Agent. What's really at issue here seems more related to proxies; is that right? That proxies were not respecting Accept-Encoding, but sending gzipped content to browsers that did not want it? Is that still a problem? Which proxies were broken? Are they still broken? And, while I understand the reluctance to help me figure out from our module what values were passed to SetEnvIfNoCase and Header, I would like to see whether there's agreement that the Apache 2.2 docs for mod_deflate are no longer appropriate -- and in fact harmful. -Josh On Sat, Jun 4, 2011 at 5:03 PM, Ben Noordhuis <i...@bnoordhuis.nl> wrote: > On Sat, Jun 4, 2011 at 21:26, Joshua Marantz <jmara...@google.com> wrote: > > I think what we'd do is basically let mod_pagespeed ignore > "Vary:User-Agent" > > if we saw that it was inserted per this exact pattern. This would, to be > > This seems like a stupendously bad idea. Warn about it in your docs, > complain about it in the logs but don't willy-nilly override people's > settings. >
