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Re: Fault-tolerance in web services

• To: Seetharama Rao Durbha <Seetharamarao.Durbha@S...>
• Subject: Re: Fault-tolerance in web services
• From: "Chiusano Joseph" <chiusano_joseph@b...>
• Date: Tue, 31 Aug 2004 09:43:13 -0400
• Cc: "'Rex Brooks'" <rexb@s...>, xml-dev@l...
• Organization: Booz Allen Hamilton
• References: <C6DA914CA56FD811BF3B00B0D049C7760A5575@NT_SERVER1>

Seetharama Rao Durbha wrote:
> 
> I thought so - but then was not quite sure if a solution akin to the web
> load balancing/fail-over is a better one, or giving individual control to
> the customers is a better one. 

Not sure what you're driving at here - load-balancing should be provided
if required, wherever it is required - that is, whether one is a service
provider or service consumer - or both - should not make a difference.
It's all about whether or not it is required given the load.

> The advantage with current way (of providing
> load-balancing / fail-over at the network service provider or perimeter) is
> that it is already in place, at least for those people with high content and
> visits. However, I am sure that Orgs with high-content web requests are not
> the ones who need to provide highly reliable web services (at least not
> 1-1), so others would need different solutions. 

Web Services reliability is actually a different, but somtimes related,
topic that involves quality of service (QoS) requirements such as
guaranteed delivery and guaranteed message ordering (see the work that
we have been doing in OASIS WS-Reliability). An example of these being
related is where a receiving system does not have adequate load
balancing capabilities, and a response to a sent message (using
reliability features) is not received by the sender within a predefined
window - which will cause either a resend or a termination of attempts
to resend that message, depending on the number of attempts vs. some
predefined parameter on the sender side.

> And, probably, making the
> choices part of the WSDL, 

If you mean the choice of using load balancing or not, then this could
be incorporated into a WSDL document in the manner described below
(multiple soap:address values). Of course, simply having multiple
addresses does not mean that load balancing is done - it just sets up
the foundation for it.

> or a dynamic retrieval of those choices from a
> UDDI repository (basically a standards-based way) would be a good idea.

Yes, one can use UDDI to dynamically retrieve a WSDL document of course.
So if this means retreiving a WSDL document that contains multiple
soap:address values, then that is on target. 

> I will take a look at WSRP.

I don't believe that WSRP incorporates the notion of load balancing into
their spec (at least the last I read), because it's more of an
implementation issue. Rex will correct me if I am wrong.

Kind Regards,
Joe Chiusano
Booz Allen Hamilton
Strategy and Technology Consultants to the World

> Thanks,
> Seetharama
> 
>  -----Original Message-----
> From:   Rex Brooks [mailto:rexb@s...]
> Sent:   Monday, August 30, 2004 7:17 AM
> To:     Chiusano Joseph; Seetharama Rao Durbha
> Cc:     xml-dev@l...
> Subject:        Re:  Fault-tolerance in web services
> 
> Indeed, not naive at all. Load balancing and
> scalability issues are here already in WSRP, and
> will need to be taken into account by IT
> architects as they begin to fashion portal-based
> IT solutions end to end of an enterprise.
> Although heterogeneous environments can be
> accommodated, the tier of largest companies will
> almost certainly need to rethink IT strategies in
> terms of investing in the most efficient and
> scalable systems. That is going to be more
> efficient with systems designed to scale from day
> one AND work with more heterogeneous partners.
> Not easy. Not simple.
> 
> Ciao,
> Rex
> 
> At 3:51 PM -0400 8/30/04, Chiusano Joseph wrote:
> >That doesn't seem at all like a naïve question, especially since your
> >additional information is right on the mark. The situation you imagine
> >is - I am certain - often done in practice, by offering a service at
> >multiple addresses.
> >
> >Kind Regards,
> >Joe Chiusano
> >Booz Allen Hamilton
> >Strategy and Technology Consultants to the World
> >
> >Seetharama Rao Durbha wrote:
> >>
> >>  Just a naïve question - fault tolerance in web services - for example,
> >>  providing multiple service/soap:address - should that be part of a
> WSDL/SOAP
> >>  client functionality, or should that be a native support provided by the
> >>  provider?
> >>
> >>  I can imagine situation where services are multi-hosted and a particular
> >>  provider would like to be able to explicitly identify those locations to
> the
> >>  clients, in case one fails, or even for load-balancing, if that is a
> >>  concern.
> >>
> >>  Thanks,
> >>  Seetharama Rao Durbha
> >>  Cell : 510-673-1843
> >>  Office : 510-742-4228
> >>
> >>  -----------------------------------------------------------------
> >>  The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
> >>  initiative of OASIS <http://www.oasis-open.org>
> >>
> >>  The list archives are at http://lists.xml.org/archives/xml-dev/
> >>
> >>  To subscribe or unsubscribe from this list use the subscription
> >>  manager: <http://www.oasis-open.org/mlmanage/index.php>
> >
> >--
> >Kind Regards,
> >Joseph Chiusano
> >Associate
> >Booz Allen Hamilton
> >
> >-----------------------------------------------------------------
> >The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
> >initiative of OASIS <http://www.oasis-open.org>
> >
> >The list archives are at http://lists.xml.org/archives/xml-dev/
> >
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> 
> --
> Rex Brooks
> GeoAddress: 1361-A Addison, Berkeley, CA, 94702 USA, Earth
> W3Address: http://www.starbourne.com
> Email: rexb@s...
> Tel: 510-849-2309
> Fax: By Request
> 
> -----------------------------------------------------------------
> The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
> initiative of OASIS <http://www.oasis-open.org>
> 
> The list archives are at http://lists.xml.org/archives/xml-dev/
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-- 
Kind Regards,
Joseph Chiusano
Associate
Booz Allen Hamilton

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