Re: ID for Immutable

Kari Hurtta <hurtta-ietf@elmme-mailer.org> Fri, 28 October 2016 15:46 UTC

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To: Alex Rousskov <rousskov@measurement-factory.com>
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From: Kari Hurtta <hurtta-ietf@elmme-mailer.org>
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Subject: Re: ID for Immutable
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Alex Rousskov <rousskov@measurement-factory.com>om>: (Fri Oct 28 18:23:54 2016)
[ Charset windows-1252 converted... ]
> On 10/28/2016 08:44 AM, Kari Hurtta wrote:
> > If server can't calculate hash-function over resource,
> > is is really static non-caching resource?
> 
> There is sometimes a big difference between the _ability_ to calculate a
> hash and the _expense_ of doing so. AFAICT, immutable responses may
> still be dynamically generated (or otherwise costly to produce) on the
> origin server.
> 
> For example, loading, encoding, and hashing a 2-hour video of the 1948
> Olympics opening ceremony could be rather expensive, but will produce
> the same immutable result [until the server has to inject a fresh set of
> advertisements sometime tomorrow].

Yes, that is valid concern.
 
> Alex.


And calculating may be even mode expensive for client. Server
needs do it only once. Not for every request. After all supposed usage 
was that resource for same URL is not updated. 

So new advertisements produce new URL for that a 2-hour video of the 
1948 Olympics opening ceremony.

But these cases client anyway will not cache resource so
immutable does not help.

/ Kari Hurtta