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From Mark Nottingham <>
Subject Re: canned deflate conf in manual -- time to drop the NS4/vary?
Date Fri, 04 Jun 2010 09:18:05 GMT

On 04/06/2010, at 6:51 PM, wrote:
> I think you need to do a reboot on your definition of 'anecdotal'.

Good for you.

> The thread above was a focused discussion about what ACTUALLY
> happens if you try to 'Vary:' on 'User-Agent' in the real world
> these days accompanied by some additional (relevant) information about
> what COULD (actually) happen if you (alternatively) try to 'Vary:' on
> 'Accept-encoding:'. If you still think any of it 'lacks veracity'
> and is 'not trustworthy' then my only suggestion would be to spend
> a little time on Google or Bling. It's an ongoing 'story'.

I'm not sure why you're using so many quotes, unless you're trying to put words into my mouth.
Please stop.

> > certainly no reproducible tests.
> What sort of tests would you like to see?

Ones that can be reproduced. Preferably in an automated fashion, or at least with demonstrable
proof. Waving around the phrase "kernel debugger" doesn't count.

> The 2.5 release of SQUID ( Early 2004 ) was the very FIRST version of that 
> Proxy Server that made any attempt to handle 'Vary:' headers at all. Prior to
> that, they were just doing the same thing all the browsers would. If a 'Vary:'
> header of ANY description arrived in the stream, it was simply treated as if
> it was 'Vary: *' ( STAR ) and there was no attempt to cache it at all.

What's your point? The deployment footprint of 2.4 is vanishingly small, given that it had
a LOT of bugs, hasn't been supported for years, and still uses select/poll. 

> If you Google 'Vary Accept-Encoding Browsers SQUID' but also include
> Robert Collins name you'll find more than if you use 'Henrik's' name
> since he was ultra-focused on the ETag thing. ( He still is ).

Yes, as am I, and Roy for that matter, last time I talked to him about it.

> Only about 12 months ago one of the SQUID User's forum lit up with another
> 'discovered' problem surrounding all this 'Vary:' stuff and this had
> to do with non-compliance on the actual 'Accept-Encoding:' fields
> themselves coming from Browsers/User-Agents. ( Browser BUGS ).
> In some cases the newly discovered problem reflects the same nightmare 
> seen TODAY with the out-of-control use of 'User-Agent'. 

It's not a bug in the implementations, it's a grey area in 2616 that HTTPbis has since worked
to resolve;

> Too many variants being generated.
> Squid User's Forum...
> Here's just a sampling of what was being shown from REAL WORLD
> Server logs just 12 months ago... 
> Accept-Encoding: FFFF, FFFFFFF
> Accept-Encoding: mzip, meflate
> Accept-Encoding: identity, deflate, gzip
> Accept-Encoding: gzip;q=3D1.0, deflate;q=3D0.8, chunked;q=3D0.6,
> identity;q=3D0.4, *;q=3D0
> Accept-Encoding: gzip, deflate, x-gzip, identity; q=3D0.9
> Accept-Encoding: gzip,deflate,bzip2
> Accept-Encoding: nnnnndeflate
> Accept-Encoding: x-gzip, gzip
> Accept-Encoding: gzip,identity
> Accept-Encoding: gzip, deflate, compress;q=3D0.9
> Accept-Encoding: gzip,deflate,X.509
> Yada, yada, yada...

Yes, yes, but in the REAL WORLD (as you like to say), there are only a few common browser
families, and there is a high degree of similarity within those families. Caches may see some
duplication, but the replacement algorithms will generally do the right thing. In the meantime,
we'll fix header normalisation in Squid, Traffic Server and other caches.

I'm not necessarily agreeing with those who say that GZIP should be turned on by default in
Apache now, but I hate to see the argument against it made with so many shoddy straw-men.

> People get REALLY PISSED these days when everything was running along
> just fine and suddenly there are 'problems'. Heads can roll.

Why don't you just shout "BOO" and get it over with?

*shakes head*

Mark Nottingham

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