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RE: Multi-server HTTP

From: : Robert Siemer <Robert.Siemer-httpwg@backsla.sh>
Date: Thu, 27 Aug 2009 09:40:29 +0800
To: ietf-http-wg@w3.org
Cc: Alan Ford <alan.ford@roke.co.uk>, Mark Handley <m.handley@cs.ucl.ac.uk>
Message-Id: <1251337230.2984.495.camel@asus-1130818068>
On Wed, 2009-08-26 at 22:30 +0200, Henrik Nordstrom wrote:
> tis 2009-08-25 klockan 10:24 +0100 skrev Ford, Alan:
> > Well that would certainly be a great solution for many use cases. If
> > there was a distributed set of virtual hosts of a given server, I can
> > see that working quite well. Plus, this would solve the ETag issue that
> > I mention (assuming I have understood correctly - nobody has yet
> > corrected me!), since in this case the client /is/ requesting the same
> > resource from each IP address.
> 
> ETag is per URI, but it is entirely fine for a specification like this
> to require that the participating servers use the same ETag for the same
> object version, for example based on an hash of the object data. How
> servers compose ETag is outside of HTTP specification and a property of
> the server implementation, only requirement HTTP places is uniqueness
> among versions or variants of the same URI. The base HTTP specifications
> places no direct requirements on how ETag from different URIs relate to
> each other, but do hint that for objects having multiple URIs where
> those URIs are equal it's expected the ETag would also be the same.


“having multiple URIs where those URIs are equal” means that they do not
have multiple URIs.

And:
-the HTTP spec only talks about when it MUST/SHOULD change, it can
change in other cases at will (bashing the caches and/or making the DNS
Round Robin use case weaker)
-Apache is configurable on what it takes into account for the ETag,
which helps into making that setup easier (use size and timestamp; and
rsync for syncing)


Robert
Received on Thursday, 27 August 2009 01:41:15 GMT

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