W3C home > Mailing lists > Public > ietf-http-wg-old@w3.org > January to April 2000

RE: On pipelining -Reply -Reply

From: Larry Masinter <LM@att.com>
Date: Fri, 21 Jan 2000 11:11:51 -0800
To: "HTTP Working Group" <http-wg@hplb.hpl.hp.com>
Message-ID: <NDBBKEBDLFENBJCGFOIJMEMNCBAA.LM@att.com>
(mailing list name 'cuckoo' -> 'hplb' again).

There's no point in restricting side effects in general; the
idea was to restrict side effects that somehow mattered! And
whether or not it matters depends on the application. For the
traditional web browsing application, clicking on a link twice,
refetching a web page, or even prospectively fetching a page
that you think someone *might* want, using GET to mirror a site,
etc ... those shouldn't have significant side effects.

For interactions between subsequent requests and pipelining,
since it is the client that decides whether to pipeline,
it is also the client that has the responsibility for
deciding whether pipelining matters.

For web browsing, there's no real problem: the only
state change where consistency matters is the interaction
between the POST from a form being filled and the subsequent
GETs that are triggered by embedded URLs in the content
that is returned from the post.

For other applications that are being built on top of
HTTP, there must be some agreement between client and
back-end application as to what the dependencies and
transaction semantics must be; the HTTP server needn't
enforce these, since the clients have complete control
over whether they ATTEMPT pipelining.

I suppose you might want to note that intermediaries
shouldn't introduce pipelining (e.g., by prospectively
guessing what URLs might appear in subsequent content
and prefetching them!) but otherwise, this is a client,
not a server, responsibility (IMO).

Servers need not serialize processing pipelined requests;
clients that care shouldn't pipeline.

Larry
-- 
http://larry.masinter.net
Received on Friday, 21 January 2000 19:15:48 EST

This archive was generated by hypermail pre-2.1.9 : Wednesday, 24 September 2003 06:33:35 EDT