On Sun, Jun 5, 2011 at 00:34, Joshua Marantz <jmara...@google.com> wrote: > 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.
This was indeed a (since fixed) problem with IE6. I haven't seen the gzip issue crop up since but that is purely anecdotal. > 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? Some popular OSS packages depend on Vary: User-Agent to make downstream proxies (reverse or forward) do the right thing. > 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. I've been mulling it over for 10 minutes and I can't decide. It's harmful because it leads to a proliferation of cached objects (bad) but removing it from the documentation will break things for someone somewhere (also bad).