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Re: ETags and concurrency control

From: Julian Reschke <julian.reschke@gmx.de>
Date: Fri, 02 May 2008 20:52:26 +0200
Message-ID: <481B62EA.2020609@gmx.de>
To: Werner Baumann <werner.baumann@onlinehome.de>
CC: ietf-http-wg@w3.org

Werner Baumann wrote:
> 
> I want to remind of how Apache and IIS use weak etags:
> 
> They create weak etags when the time of the request is within the same 
> second as the last modified date of the resource. This weak etags simple 
> mean:
> - if the etag matches, the entity is most probably unchanged, but there 
> is a small chance, that it changed.
> - if the entity changed, it may have changed into anything; there is 
> absolutely no check for anything like semantic equivalence.
> 
>  From this common use of weak etags, it makes sense to not allow weak 
> etags in PUT (lost update problem), but to allow it in full body GET (in 
> case the entity changed, the damage is usually small).
> ...

I'd say that it's the server's choice to generate these kinds of ETags. 
Nut if it does, and they aren't reliable enough for a write operation, 
it could still reject the request... My understanding was that we want 
*allow* servers to support weak etags on write operations, not require.

> ...

BR, Julian
Received on Friday, 2 May 2008 18:53:07 GMT

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