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Re: [widgets] ETags and Automatic updates

From: Marcos Caceres <marcosscaceres@gmail.com>
Date: Thu, 3 Jul 2008 16:23:36 +1000
Message-ID: <b21a10670807022323w5a37b599ha69b92a7750a5ac0@mail.gmail.com>
To: "Julian Reschke" <julian.reschke@gmx.de>
Cc: "mike amundsen" <mca@amundsen.com>, "Web Applications Working Group WG" <public-webapps@w3.org>

On Thu, Jul 3, 2008 at 3:34 PM, Julian Reschke <julian.reschke@gmx.de> wrote:
> Marcos Caceres wrote:
>> On Wed, Jul 2, 2008 at 10:17 PM, mike amundsen <mca@amundsen.com> wrote:
>>> Marcos:
>>> <snip>
>>>> I'm sure it could be done. But how can this be done easily with Apache
>>>> or IIS?
>>> </snip>
>>> Since Apache and IIS are HTTP servers, you can use the HTTP Headers to
>>> send hash data. Using the ETag is the most common, but if you like,
>>> you can propose a new HTTP Header ("X-Widget-Hash").
>> I know I should be able to do to send HTTP headers, but the question
>> is still *how*? I mean, for Apache, do I modify the .htaccess file? if
>> so, what do I put in there? If I can get a web server to send a custom
>> ETag or Widget-Hash easily enough, then the solution is doable so long
>> as its also easy to replicate in IIS and on any other web server.
> *Sending* a custom etag is not sufficient; Apache needs to be aware of it,
> otherwise all the conditional HTTP stuff will stop working.

Yeah, this is kinda what I'm getting at :)

>> FWIW, if it comes down to having to introduce a custom HTTP header,
>> then I definitely think we should dump this solution.
> What about Content-MD5?

Not supported by IIS, AFAIK.

In Apache, sure, but, as [1] states, "Note that this can cause
performance problems on your server since the message digest is
computed on every request (the values are not cached)."

And [2] says "It was a bit proof-of-content code I added to Apache,
and was never designed to be used in a real web server...."

[1] http://apache.active-venture.com/mod/core3.htm
[2] http://mail-archives.apache.org/mod_mbox/httpd-dev/199708.mbox/%3CPine.GSO.3.95.970824131548.24509A-100000@veal.organic.com%3E

Marcos Caceres
Received on Thursday, 3 July 2008 06:24:19 UTC

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