Hi Ken,
It's an interesting posting. The EF is getting more involved with
OSGi standardization efforts...I think that Jeff is heavily involved
with Peter and others on exactly this effort. Jeff would you care to
comment on what you see as the right role for Equinox, ECF, and/or this
remoteservices API in this?
Thanksinadvance,
Scott
Ken Gilmer wrote:
This post on the OSGi.org blog is relevant to this discussion:
-Ken
On Sep 12, 2006, at 9:30 PM, Jeff McAffer wrote:
Sounds like fun! I have not been
following the ins and outs of ECF much so please excuse any ignorant
questions...
- do you see a path to this being
integrated with declarative services and/or Spring and whatever Spring
does for remoting?
- do you see integrating
with/using concurrency constructs like Futures whith remove services?
- can I assume that under the
covers you can use any transport to contact the remote service?
- do you know where I can find
some spare time to play with all the great things people are creating
these days? ;-)
Jeff
Hi Folks,
Although not completed, a 'signs of life' ECF remote service API is now
functioning with test code. The intention of this API is to provide
access to remote services similar to the manner in which OSGI provides
access to local services via OSGi service registry.
The remoteservice API, however, is *not* the same as the OSGi service
API, in recognition/acknowledgment of the problems introduced by
approaches that attempt network transparency. The remoteservice API
exposes a distinct API and underlying service registry, similar in
structure to the OSGi services API, but with modifications to account
for 1) the use of asynchronous messaging; 2) partial failure.
The three plugins in CVS are:
plugins/org.eclipse.ecf.remoteservice (API)
plugins/org.eclipse.ecf.provider.remoteservice (exampleprovider)
plugins/org.eclipse.ecf.test.remoteservice (JUnit Plugin test code)
As a brief example, here's how a remote service is registered/made
available for remotes to access. This is done on the client that is
the
server for this particular service
// First get IRemoteServiceContainer adapter
IRemoteServiceContainer rsc = (IRemoteServiceContainer)
container.getAdapter(IRemoteServiceContainer);
// Then register remote service
rsc.registerRemoteService(new String [] { IMyService.class.getName() },
service, null);
Note that the 'service' object must implement the IMyService. Assume
that IMyService has a single method "exec()". For those familiar with
the OSGI service interface, this looks very much like the
BundleContext.registerService method.
Then, on the client that wishes to use the service:
IRemoteServiceReference [] refs = rsc.getRemoteServiceReferences(null,
IMyService.class.getName(),null);
// Assume we want the first one
IRemoteService remoteService = rsc.getRemoteService(refs[0]);
// Now call service with one of methods on IRemoteService: callSynch,
callAsynch, fireAsynch, getProxy()
Note the getRemoteServiceReferences(...) and getRemoteService(...) are
similar to the OSGI BundleContext.getServiceReferences(...) and
getService(...) methods.
The methods on IRemoteService allow the client to invoke the service in
several different ways...i.e. synchronously (callSynch) or
asynchronously (callAsynch...with a listener callback for results, and
fireAsynch which fires a remote method asynchronously with no return
value). Note also the 'getProxy()' call, which will return an Object
*that is guaranteed to implement the IMyService interface*. Meaning
that one can do this:
IMyService proxy = (IMyService) remoteService.getProxy();
proxy.exec();
And the remote 'exec()' method will be remotely invoked.
So the point of the IRemoteService interface is to allow the client to
control how the remote service invocation is done...synchronously with
return value, synchronously via proxy, or asynchronously with
(callAsynch)/without (fireAsynch) return value.
There's test code in the org.eclipse.ecf.test.remoteservice test plugin
that uses these methods on IRemoteService interface. I've made put
project set files for committer and anonymous cvs access here:
http://wiki.eclipse.org/index.php/Remote_OSGI_Services
Any comments/criticisms/flames welcome. This is just an initial "signs
of life" attempt, and the API and implementation will likely go through
many changes.
Thanks,
Scott
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