Dynamic reloading of SCA Config

[devilpump <de...@gmail.com>]

Does the SCA Spec and or Tuscany allow dynamic modification of the  
sca config?
Say for instance I wanted a client app to point at a different  
location for a web service it is consuming.   Is it possible to  
change the wsdl and sca.module files at runtime without forcing  
tomcat to reload the app?   Does the SCA make any mention of changing  
bindings at runtime?  I haven't seen anything, but thought I'd ask.

Cheers,
Raf Ali 

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Re: Dynamic reloading of SCA Config

[Jeremy Boynes <jb...@apache.org>]

The quick answer is not yet.

The longer answer is, yes this is definitely one of the goals of SCA  
and for Tuscany (at least as I see it). The idea behind SCA assembly  
is to create a logical model of the services that are in use in a  
domain and the connections between them. This is an "SCA System" and  
is about a domain of control rather than a physical machine or  
collection of machines.

Once we have this model, the runtimes that physically form up the  
system can coordinate the services present and how they interact. The  
assembly represents the user's intentions for service provision and  
consumption and can be manipulated to ensure those intentions are  
fulfilled (within the constraints imposed for example through  
policy). When the user changes the assembly, the underlying platforms  
respond to those changes.

How they do that depends on the runtimes. At the moment, Tuscany's  
runtime platforms are fairly simple - what we have so far is a basic  
command line client and a simple in-webapp server. Neither of those  
is actually in control of its environment and able to respond without  
restarting. In other words, a SCA composite running in a webapp is  
connected to remote webservice using an address that can only be  
changed by redeploying the webapp. How dynamic that is is down to the  
webapp container and for Tomcat the default is not very (you need to  
reload the app).

One of the things I'd like to tackle in the next release is making  
this more dynamic. This would mean developing runtime platforms that  
can respond to changes made by the user without outage of service  
unless necessary. For a "legacy" server like the ones above, the only  
way we may be able to do it is through redeploying/reloading an  
application. The more dynamic ones would support some form of  
administration service that allows them to be reconfigured on the fly.

We have support for this in the core runtime already - you are able  
programmatically to remove/reload/reconfigure services as needed.  
What we are missing is the management services that expose this  
function to end users.

--
Jeremy

On Oct 15, 2006, at 3:12 PM, devilpump wrote:

> Does the SCA Spec and or Tuscany allow dynamic modification of the  
> sca config?
> Say for instance I wanted a client app to point at a different  
> location for a web service it is consuming.   Is it possible to  
> change the wsdl and sca.module files at runtime without forcing  
> tomcat to reload the app?   Does the SCA make any mention of  
> changing bindings at runtime?  I haven't seen anything, but thought  
> I'd ask.
>
> Cheers,
> Raf Ali
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: tuscany-user-unsubscribe@ws.apache.org
> For additional commands, e-mail: tuscany-user-help@ws.apache.org
>


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