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Re: usability of 100-continue, was: HTTP2 Expression of Interest : Squid

From: Willy Tarreau <w@1wt.eu>
Date: Tue, 17 Jul 2012 22:59:22 +0200
To: Julian Reschke <julian.reschke@gmx.de>
Cc: Osama Mazahir <OSAMAM@microsoft.com>, Gabriel Montenegro <Gabriel.Montenegro@microsoft.com>, Adrien de Croy <adrien@qbik.com>, Poul-Henning Kamp <phk@phk.freebsd.dk>, Amos Jeffries <squid3@treenet.co.nz>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Message-ID: <20120717205922.GA4338@1wt.eu>
On Tue, Jul 17, 2012 at 10:31:08PM +0200, Julian Reschke wrote:
> On 2012-07-17 21:45, Osama Mazahir wrote:
> >As it is currently, 100-continue is problematic.  The situation is 
> >tricky because the client is not forced to wait for the 100/417/4xx 
> >(i.e. client is allowed to timeout and send the entity body).  Thus, the 
> >server does not have a deterministic way to now if the next byte after 
> >the double CRLF is the first byte of the next request or the first byte 
> >of the entity body (of the initial request).  This results in 
> >connections getting closed in various edge/error cases.
> >
> >100-continue is almost there but if we wanted to use it in a robust 
> >manner in HTTP2 then I think we would have to revisit its specification.
> >...
> 
> Well, we are revising RFC 2616, and if something is broken here we 
> should consider to fix it. Or, minimally, document the problem.
> 
> If I understand correctly, this will happen if the client sends "Expect: 
> 100-continue", the server is slow to return an error status, and the 
> client decides to give up waiting for the 100 status, and continues?

I don't see how it is possible to send a next request without first sending
the entity body, the message is not complete until it has been sent as a
whole; the problem could only happen if the server wished to reject the
expectation (4xx).

Regards,
Willy
Received on Tuesday, 17 July 2012 21:00:08 GMT

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