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RE: Stateful Web Services...

From: David Orchard <dorchard@bea.com>
Date: Fri, 29 Oct 2004 14:11:46 -0700
Message-ID: <32D5845A745BFB429CBDBADA57CD41AF0B588C67@ussjex01.amer.bea.com>
To: <www-ws@w3.org>

That is an assertion that I disagree with.  You haven't proven how
stateless web services are always more scalable than stateful Web
services.  I assert that there are some cases where Web services are
more scalable if done in a stateless manner, and that these cases are
fairly easily categorized.  

Let's cut to the chase and accept a definition of Scalability as defined
by Roy.  

"Scalability refers to the ability of the architecture to support large
numbers of components, or interactions among components, within an
active configuration. Scalability can be improved by simplifying
components, by distributing services across many components
(decentralizing the interactions), and by controlling interactions and
configurations as a result of monitoring. Styles influence these factors
by determining the location of application state, the extent of
distribution, and the coupling between components.

Scalability is also impacted by the frequency of interactions, whether
the load on a component is distributed evenly over time or occurs in
peaks, whether an interaction requires guaranteed delivery or a
best-effort, whether a request involves synchronous or asynchronous
handling, and whether the environment is controlled or anarchic (i.e.,
can you trust the other components?)."

Roy specifically talks about scalability being affected by a variety of
aspects of the interaction patterns.  Which he has done in a far better
way than I have.  Notice he particularly says that the location of
application state and extent of distribution affects scalability.  He
does not say that stateless services are always the best.  It's the old
engineering answer, "it depends".  

Dave

> -----Original Message-----
> From: Mark Baker [mailto:distobj@acm.org]
> Sent: Friday, October 29, 2004 12:16 PM
> To: David Orchard
> Cc: www-ws@w3.org
> Subject: Re: Stateful Web Services...
> 
> On Fri, Oct 29, 2004 at 11:25:53AM -0700, David Orchard wrote:
> > Stateful vs stateless is really a question of trade-offs of desired
> > properties
> 
> Of course.
> 
> > that the service provider makes, and scale is not one of
> > them.
> 
> Incorrect.  Scalability is, IMO, the biggest trade off.
> 
> Mark.
> --
> Mark Baker.   Ottawa, Ontario, CANADA.        http://www.markbaker.ca
Received on Friday, 29 October 2004 21:11:48 GMT

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