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Re: Does idempotence include the response codes?

From: Gili <cowwoc@bbs.darktech.org>
Date: Tue, 15 Oct 2013 16:17:13 -0400
Message-ID: <525DA2C9.9040208@bbs.darktech.org>
To: Willy Tarreau <w@1wt.eu>
CC: Julian Reschke <julian.reschke@gmx.de>, ietf-http-wg@w3.org
On 10/15/2013 2:14 PM, Willy Tarreau wrote:
> Hi Julian,
>
> On Tue, Oct 15, 2013 at 08:05:24PM +0200, Julian Reschke wrote:
>> On 2013-10-15 19:43, cowwoc wrote:
>>> Hi,
>>>
>>>      Can the authors officially weigh in on the meaning of "idempotent"
>>> with response to response codes? Do idempotent methods have to return
>>> the same response code in the face of multiple invocations? Or are they
>>> allowed to return different response codes so long as the state is not
>>> modified by subsequent requests? See
>>> http://stackoverflow.com/q/741192/14731 for the discussion that fueled
>>> this question.
>> I'll repeat what I said over there:
>>
>> No, "effect" is not intended to cover the response as well. What you
>> propose is that DELETE either always must pass ("200") or fail ("404" or
>> "410"), no matter what the state of the server is. This doesn't make any
>> sense and furthermore doesn't help the client at all.
>>
>>>      PS: It would be nice if the spec officially clarified this point as
>>> I've seen it brought up again and again in different discussions.
>> I personally believe it's clear enough, as the other interpretation
>> frankly doesn't make any sense.
>>
>> That being said, what do others think?
> While my understanding has always been that the effect is considered on
> the server only, this question made me re-read the definition in p2-4.2.2.
>
> And trying to read it with the other meaning in mind, I find nothing which
> tells me I'm wrong :
>
>     Request methods are considered "idempotent" if the intended effect of
>     multiple identical requests is the same as for a single request.  Of
>     the request methods defined by this specification, the PUT, DELETE,
>     and safe request methods are idempotent.
>
>     [the 2 other paragraphs do not prove me wrong either]
>
> For example, people working on a client could easily consider the effect
> as "the effect on my client". I guess it would remove that question if we
> just add "on the server" after "effect" to remove this possible ambiguity.
>
> Maybe your example about DELETE returning 200 then 404 or 410 would also
> be nice to add at the end of the first paragraph quoted above.
>
> Best regards,
> Willy
>

Yes. Adding "on the server" and an example would definitely help.

Gili
Received on Tuesday, 15 October 2013 20:17:48 UTC

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