Re: Updated Prefer Header Draft

On Mon, Oct 22, 2012 at 5:48 PM, Adrien W. de Croy <adrien@qbik.com> wrote:

>
> Hi James
>
> as a proxy developer, I'm always interested in how such protocol changes
> will impact my product, and there's always the cost/benefit analysis which
> on one hand looks at what is the likely implementation rate or importance
> of sites that may choose to rely on such an extension.
>
> So do you have any information (e.g. have there been any indications from
> implementors) as to who would be looking to implement such extensions?
>
> My only other comment on the draft would be that there are some implicit
> assumptions that may not always hold (but may be ok for the general cases),
> e.g.
>
> * you can't assume your header will make it to the server, so if the
> server relies on it, or the client relies on the server receiving it, there
> would need to be some clear way to indicate this so the client can know
> whether the server received the directive or not.  E.g. intermediaries that
> strip unknown headers.
>
>

This, among other reasons, is why the entirely optional Preference-Applied
response header has been reintroduced. Further, as Mark states, the very
nature that this is a Preference and not a Requirement makes this ok.


> * you can't assume anything about how long it may take for a request to
> reach a server.  E.g. a PUT request going through a proxy that does AV
> scanning will take an unforeseeable period of time to receive, then scan
> the content before making an upstream request.  This could cause problems
> with the proposed "wait" preference.  In fact I struggle to see how "wait"
> would be used in practise, and the skeptical side of me wonders at its
> merit.
>
>

In the latest version, wait has been refactored to account for this concern.

- James


>  Regards
>
> Adrien
>
>
> ------ Original Message ------
> From: "James M Snell" <jasnell@gmail.com>
> To: "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
> Sent: 13/10/2012 7:09:54 a.m.
> Subject: Updated Prefer Header Draft
>
> The last call on the Prefer draft has closed as of today. Based on the
> excellent feedback I received during the last call, I have updated the
> current draft and it has been handed off for IESG review. The current draft
> is located here
>
>   <http://www.ietf.org/id/draft-snell-http-prefer-15.txt>
> http://www.ietf.org/id/draft-snell-http-prefer-15.txt
>
> The major changes based on feedback include:
>
> 1. I have brought back the Preference-Applied response header. I know that
> there are a few folks who feel this header is entirely unnecessary but
> feedback I have received from a number of implementers has convinced me it
> is. The use is optional and limited to cases where the application of a
> preference may not be obvious and the application of the preference could
> have an impact on the processing of a response.
>
> 2. I have altered the definition of the wait preference slightly.
> Essentially, it now specifies the clients assumption of how long processing
> a request should take rather than indicating how long the client is willing
> to wait for a response. The difference is subtle but important, and the
> change is a very good one.
>
> 3. I have made a number of editorial changes to the structure of the
> document. Some section numbers have changed.
>
> - James
>
>