p6: Vary and effects on future requests

Mark Nottingham <mnot@mnot.net> Mon, 29 April 2013 05:15 UTC

Return-Path: <ietf-http-wg-request@listhub.w3.org>
X-Original-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Delivered-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 0C7BE21F9CF9 for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Sun, 28 Apr 2013 22:15:16 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -8
X-Spam-Level:
X-Spam-Status: No, score=-8 tagged_above=-999 required=5 tests=[RCVD_IN_DNSWL_HI=-8]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 41kJzn3vI5e6 for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Sun, 28 Apr 2013 22:15:15 -0700 (PDT)
Received: from frink.w3.org (frink.w3.org [128.30.52.56]) by ietfa.amsl.com (Postfix) with ESMTP id 59E6421F9C7F for <httpbisa-archive-bis2Juki@lists.ietf.org>; Sun, 28 Apr 2013 22:15:11 -0700 (PDT)
Received: from lists by frink.w3.org with local (Exim 4.72) (envelope-from <ietf-http-wg-request@listhub.w3.org>) id 1UWgPc-0007qE-Hi for ietf-http-wg-dist@listhub.w3.org; Mon, 29 Apr 2013 05:14:04 +0000
Resent-Date: Mon, 29 Apr 2013 05:14:04 +0000
Resent-Message-Id: <E1UWgPc-0007qE-Hi@frink.w3.org>
Received: from maggie.w3.org ([128.30.52.39]) by frink.w3.org with esmtp (Exim 4.72) (envelope-from <mnot@mnot.net>) id 1UWgPY-0007ox-8K for ietf-http-wg@listhub.w3.org; Mon, 29 Apr 2013 05:14:00 +0000
Received: from mxout-08.mxes.net ([216.86.168.183]) by maggie.w3.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from <mnot@mnot.net>) id 1UWgPX-0004SD-Jn for ietf-http-wg@w3.org; Mon, 29 Apr 2013 05:14:00 +0000
Received: from [192.168.1.80] (unknown [118.209.190.66]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTPSA id 3FE33509B5 for <ietf-http-wg@w3.org>; Mon, 29 Apr 2013 01:13:37 -0400 (EDT)
From: Mark Nottingham <mnot@mnot.net>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: quoted-printable
Message-Id: <6C6BEA0B-20CC-4672-914A-C53873B8972A@mnot.net>
Date: Mon, 29 Apr 2013 15:13:37 +1000
To: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
Mime-Version: 1.0 (Mac OS X Mail 6.3 \(1503\))
X-Mailer: Apple Mail (2.1503)
Received-SPF: pass client-ip=216.86.168.183; envelope-from=mnot@mnot.net; helo=mxout-08.mxes.net
X-W3C-Hub-Spam-Status: No, score=-4.3
X-W3C-Hub-Spam-Report: AWL=-2.432, BAYES_00=-1.9, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001
X-W3C-Scan-Sig: maggie.w3.org 1UWgPX-0004SD-Jn 571317f8376600ddcfb38ec816a58e53
X-Original-To: ietf-http-wg@w3.org
Subject: p6: Vary and effects on future requests
Archived-At: <http://www.w3.org/mid/6C6BEA0B-20CC-4672-914A-C53873B8972A@mnot.net>
Resent-From: ietf-http-wg@w3.org
X-Mailing-List: <ietf-http-wg@w3.org> archive/latest/17652
X-Loop: ietf-http-wg@w3.org
Resent-Sender: ietf-http-wg-request@w3.org
Precedence: list
List-Id: <ietf-http-wg.w3.org>
List-Help: <http://www.w3.org/Mail/>
List-Post: <mailto:ietf-http-wg@w3.org>
List-Unsubscribe: <mailto:ietf-http-wg-request@w3.org?subject=unsubscribe>

p6 4.3 says:

"""A Vary header field value of "*" always fails to match, and subsequent requests to that resource can only be properly interpreted by the origin server."""

Someone reading this could take away that *any* stored response with a Vary: * has an effect on ALL other stored responses that share that primary key (and a couple of the issues we discussed reflected this confusion, from memory).

As I recall, the goal for 4.3 Using Negotiated Responses was to assure that stored responses were independent and self-describing; i.e., that a cache didn't have to rationalise the value of the Vary header among multiple stored responses.

So, I'd suggest changing this to just:

"A Vary header field value of "*" always fails to match."

Make sense?


--
Mark Nottingham   http://www.mnot.net/