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Re: [ecf-dev] Re: pub sub example and distributed OSGI service registry

Personally, I feel much safer about model replication along w/ MDD/ MVC style applications rather than code calling code in a distributed fashion.

I don't understand what you mean with this Ken. Do you mean that with model replication the service is meant to transparently look to clients as if it's 'local'?
e.g. a client could get a local reference and cast to appropriate type:

I mean, rather than using the OSGi Service" functionality (service discovery, advertising, and consumption) as a way to bind isolated runtime environments together, using a passive model (ie, no application-level remote code calling) by which operations are performed against a domain model, which is then replicated across peers using something like Datashare. So I would have some sort of model bundle that hosted a model. The model would be exposed to my other local bundles via a traditional OSGi service interface. However no ECF related functionality would be exposed. The model bundle would internally use ECF to perform replication and change notification. Of course, as said in previous emails, the "distributed OSGi services" approach has been developed before (flowOSGI.pdf). I would be curious to play around with distributed OSGi services, but would be inclined to avoid them in general, mainly due to the issues described in the "A Note on Distributed Computing".


-Ken


On Jul 18, 2006, at 5:56 PM, Scott Lewis wrote:

Hi Ken,

Ken Gilmer wrote:

with the remote service: 1) IRemoteService.callSynch(...): which would provide blocking call/return semantics; 2) IRemoteService.callAsynch(...) (either one) which sends a message to remote service, and either uses polling (AsynchResult) or notification to receive a return value; and 3) IRemoteService.fire (...): which would simply send a one-way message to invoke the remote service but not expect or wait for a return value.

So there would be no explicit Java interface binding?

There could be explicit java interface binding as well (i.e. proxies). The IRemoteService API could have a method Object IRemoteService.getService() that by contract would expose an Object that implemented the interfaces specified in the registerRemoteService(...) call.
The methods currently listed on IRemoteService is intended to allow explicit support for one-way (fire) and asych invocation (callAsynch). I probably should have already made this clear and added getService().


How would complex types as parameters be handled?

Through Object [] parameters...using/assuming autoboxing for primitive types.


Personally, I feel much safer about model replication along w/ MDD/ MVC style applications rather than code calling code in a distributed fashion.

I don't understand what you mean with this Ken. Do you mean that with model replication the service is meant to transparently look to clients as if it's 'local'?
e.g. a client could get a local reference and cast to appropriate type:


IMyServiceInterface service = (IMyServiceInterface) container.getRemoteService(remoteReference).getService();
// call it...hiding the fact that the model is actually replicated locally
int result = service.getMyValue("foo");


Is this what you mean or am I misinterpreting?

Thanks,

Scott


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