Hi,

First of all, let me say that Orocos is an amazing framework.
Actually, I was looking for a framework with the following capabilities.

• Xenomai enabled
• CORBA object distribution
• Dynamic object loading (preferrably via XML)

Needless to say that Orocos was the perfect match.

Right now, I have a bunch of TaskContexti's deployed with the DeploymentComponent. This all works as expected.

I then tried to export my DeployementComponent object on the network. That worked fine too and I could see my object on the TAO NameService using /usr/bin/nslist (tao-utils).
Then, I created a separated (CORBA) client which retrieves a proxy to that object using the ControlTaskProxy object. The proxy seemed to work OK since I could retrieve the list of peers (which matched the list of TaskContexts that I deployed server-side with my DeploymentComponent).

My problem is that I can't do the following:

Methodi<void(long)> m = proxy->getPeer("Processor")->methods()->getMethod<void(long)>("doSomeStuff");
m(1);

I get a "No such method" error.

It is my understanding that methods of the peers of a ControlTaskProxy are dynamically created on the client side meaning that my code should probably work. Then again, I suppose I missed something obvious.

I also did some tests on orocos-apps/examples/corba-example/SingleProcess.cxx. I modified the file as follows:

connectPorts( &local, mtask );
// Modifications - begin

        std::cout << "ExecutionPeer present: " << local.hasPeer("ExecutionPeer") << std::endl;
        std::cout << "Number of methods on Execution peers (getNames): " << local.getPeer("ExecutionPeer")->methods()->getNames().size() << endl;
        std::cout << "Number of methods on Execution peers (getMethods): " << local.getPeer("ExecutionPeer")->methods()->getMethods().size() << endl;

// Modifications - end

        TaskBrowser browser( &peer );

When I run the newly compiled eprocess, I get the following output:
ExecutionPeer present: 1
Number of methods on Execution peers (getNames): 20
Number of methods on Execution peers (getMethods): 0

What puzzles is me that the last two calls do not give the same number. Why is the second call giving me 0 methods (that would explain why I can't do a getMethod())?

Thanks in advance for any pointers and keep up the great work with Orocos.

Viktor STARK

On Tuesday 26 February 2008 18:10:34 Viktor Stark wrote:
> [Accidentally first sent to orocos at lists [dot] mech [dot] kuleuven [dot] be by mistake.]

Oops, I forwarded that one to orocos-users as well...I hadn't noticed your
repost.

[...]
> My problem is that I can't do the following:
>
> Methodi<void(long)> m =
> proxy->getPeer("Processor")->methods()->getMethod<void(long)>("doSomeStuff"
>); m(1);
>
> I get a "No such method" error.

This functionality relies on a yet unfinished part of the CORBA API, but a
work-around is provided. For (about) the same functionality, you can use the
MethodC class:
<http://www.orocos.org/stable/documentation/rtt/v1.4.x/api/html/classRTT_1_1MethodC.html>
and see also rtt/tests/corba-test.cpp for examples.

MethodC m = proxy->getPeer("Processor")->methods()->create("doSomeStuff");

long arg1 = 1;
m.arg( arg1 ); // takes reference to 'arg1'
arg1 = 2;
assert( m.ready() );
m.execute(); // uses '2'.

Ok. So this works. Now for the experimental support part:

I started on writing wrapper classes which use the MethodC/CommandC behind the
scenes and lets the user use the Method<void(long)> API as usual.
The 'RemoteCommand' class was my first prototype and wraps around a CommandC.
At that time, there was little demand for CORBA, so I didn't finish it. Then
you came along :-)

So I couldn't resist. I finished the RemoteCommand and RemoteMethod
implementations, you can apply the patch in attachment on the RTT source
tree, and try it again:
cd orocos-rtt-1.4.0
patch -p0 < corba-remoting.patch
cd build; make && make install

However, I did not get 'references' (double& d) as arguments or return values
working. It will compile, but they will not work as expected. For the rest, I
unit-tested the code for local methods and CORBA methods. Both worked fine.

>
> It is my understanding that methods of the peers of a ControlTaskProxy are
> dynamically created on the client side meaning that my code should probably
> work. Then again, I suppose I missed something obvious.

The interface was recreated, but there was no (easy) means to use it yet from
C++

>
> I also did some tests on
> orocos-apps/examples/corba-example/SingleProcess.cxx. I modified the file
> as follows:
>
> connectPorts( &local, mtask );
> // Modifications - begin
> std::cout << "ExecutionPeer present: " <<
> local.hasPeer("ExecutionPeer") << std::endl; std::cout << "Number of
> methods on Execution peers (getNames): " <<
> local.getPeer("ExecutionPeer")->methods()->getNames().size() << endl;
> std::cout << "Number of methods on Execution peers (getMethods): " <<
> local.getPeer("ExecutionPeer")->methods()->getMethods().size() << endl; //
> Modifications - end
> TaskBrowser browser( &peer );
>
> When I run the newly compiled eprocess, I get the following output:
> ExecutionPeer present: 1
> Number of methods on Execution peers (getNames): 20
> Number of methods on Execution peers (getMethods): 0
>
> What puzzles is me that the last two calls do not give the same number. Why
> is the second call giving me 0 methods (that would explain why I can't do a
> getMethod())?

Yes. getNames() shows you which methods are available to the CORBA and
scripting layers, getMethods() shows you which methods are locally available
in the C++ layer. For remote objects, getMethods() will return 0. My patch
does not change these return values, but makes that the
getMethod<...>("name") function can be used for CORBA methods as well.

>
> Note: If I use the bin/ctaskbrowser with my NameService reference as
> parameter, I can access all the peers and their methods so my "base setup"
> seems to be working OK. My only problem is that I want to retrieve remote
> method references inside my code (i.e. not using TaskBrowser).
>
> Thanks in advance for any pointers and keep up the great work with Orocos.

Thanks for the positive feedback :-) I'll open a Bug report for this work.

Peter