Sorry for the delay in getting back to this mail thread. I talked with Mark
Nottingham, chair of the HTTP WG in the IETF, who, to be clear, is in no way
responsible for the content of this email.
Nevertheless he did say that so long as one probes the connection then
pipelining is known to work. Probing just means that you can't assume that the
server you are talking to is a 1.1 server and therefore supports pipelining. So
you have to make the first request, get back a 1.1 response and only then make
the second and subsequent requests with pipelining.
I would think it would be easier to teach people how to do probing than to
introduce a completely new compound message format. But I recognize that is
just my opinion, not a fact.
So please just take this a comment from the peanut gallery.
Thanks,
Yaron
> -----Original Message-----
> From: Jens Alfke [mailto:[email protected]]
> Sent: Friday, January 24, 2014 11:36 AM
> To: [email protected]
> Subject: Re: _bulk_get protocol extension
>
>
> On Jan 24, 2014, at 9:35 AM, Yaron Goland <[email protected]> wrote:
>
> > In the HTTP WG more than a decade ago issues like this came up under the
> name 'boxcar'ing'. But with the introduction of pipelining the performance
> benefits of boxcar'ing for idempotent requests went away.
>
> It's not that simple. Pipelining has problems, as described by Ilya Grigorik
> in
> his excellent new book "High Performance Browser Networking":
>
> >> In practice, due to lack of multiplexing, HTTP pipelining creates
> >> many subtle and undocumented implications for HTTP servers,
> intermediaries, and clients: [...] Due to these and similar complications, and
> lack of guidance in the HTTP 1.1 standard for these cases, HTTP pipelining
> adoption has remained very limited despite its many benefits. Today, some
> browsers support pipelining, usually as an advanced configuration option, but
> most have it disabled.
>
> -
> http://chimera.labs.oreilly.com/books/1230000000545/ch11.html#HTTP_PIPE
> LINING
>
> In my case, pipelining is off by default in Apple's HTTP client framework, and
> I've been loath to turn it on for reasons like those Grigorik describes.
> (Also,
> IIRC I tried turning it on a year or so ago and ran some replication
> performance tests, and didn't see noticeable improvements.)
>
> Coalescing everything into one request also removes the overhead of
> generating and parsing each HTTP request/response, on both client and
> server sides.
>
> -Jens
