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Re: Stateful Web Services...

From: Mark Baker <distobj@acm.org>
Date: Fri, 29 Oct 2004 16:30:28 -0400
To: "Mullins, Chalon" <Chalon.Mullins@schwab.com>
Cc: 'Savas Parastatidis' <Savas.Parastatidis@newcastle.ac.uk>, www-ws@w3.org, Ian Foster <foster@mcs.anl.gov>, Carl Kesselman <carl@ISI.EDU>, Steve Graham <sggraham@us.ibm.com>, Steve Tuecke <tuecke@mcs.anl.gov>
Message-ID: <20041029203028.GD14710@markbaker.ca>

Hi again,

On Fri, Oct 29, 2004 at 12:50:07PM -0700, Mullins, Chalon wrote:
> <MB> In my experience with scaling Web servers, what gets in the way is
> exactly the mechanism you describe there; "storing it on the back end,
> and passing information about how to get at it".  By doing that, you
> prevent the server from freeing up resources as it needs, and end up
> requiring hacks like distributed garbage collection, and/or just
> throwing more and more server resources at the problem.
> <CM>  Exactly!  We get the benefit that we can scale our applications by
> adding or taking away servers without impacting clients, but, as things
> stand, we have to take care of these issues ourselves.

Ok, sure, but I claim that stateful apps have to upgrade much more often
since they're maintaining state which isn't present for stateless apps
(since it's all in the messages).

>  I would draw a
> different conclusion, though:  this is exactly why a standard way of
> handling the inherent statefulness of the problem in a stateless protocol is
> key -- then the server can understand what's going and free up resources,
> etc.  Not surprising that the Grid Community, which runs up against this
> problem all the time, would be the one pushing the standard solution.

Well, I personally feel that the Grid community has made a mistake by
so fully embracing stateful comms with WS-RF.  YMMV, of course. 8-)

> <MB> I think you'd be surprised what you could handle.  Most of the
> interesting work on scalable services over the past 10 years or so
> has been done with Web servers.
> <CM> Interesting claim, but I'm not sure what backs it up.  I think you're
> dismissing some really fascinating things that have been done, for example,
> in the mainframe space.  BTW -- we are always testing the limits of what we
> can handle.

No, I'm not too familiar with mainframes.  I should have stated that
most of the *published* work on scalability of network based services
has been regarding Web server scalability; "interesting" is, of
course, subjective. 8-)

But if you had any pointers handy to the work you're referring to, I'd
love to have a look.  TIA!

> <MB> There could very well be some scenarios for which that doesn't make
> sense, but in my experience stateless should always be your first choice
> unless there's a darned good reason not to use it.
> <CM> Well, I agree about going "stateless," but as the dialog that started
> this point explained, I think we have differences over just what that means.
> As far as whether we really do have a scenario that doesn't fit, I'm
> comfortable that we have.  And we may just have to disagree on that point.

Yes, it seems so! 8-)


Mark Baker.   Ottawa, Ontario, CANADA.        http://www.markbaker.ca
Received on Friday, 29 October 2004 20:28:43 UTC

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