[omniORB] ServantLocator and ForwardRequest in Python

[baileyk@schneider.com]

I'm trying to translate some C++ code that I started working on (an
adaptive load balance service similar to one described in a paper by Doug
Schmidt) into Python since I think I'll get a prototype completed faster
that way.  Below is some of the relavent pieces.  I'm having trouble
getting a successful location forward to work using omniORBpy.

C++:
==============
// class declaration
class MigratorImp :
   public virtual POA_PortableServer::ServantLocator

// preinvoke method snippet:
      PortableServer::ForwardRequest fwd;
      cout << "Migrating" << endl;
      CORBA::Object_var b = // get the real object ref somehow
      fwd.forward_reference =
             CORBA::Object::_duplicate(b.in());
      throw fwd;

// setup the POA
   policies[i++] = poa->create_thread_policy(
                         PortableServer::SINGLE_THREAD_MODEL );
   policies[i++] = poa->create_request_processing_policy(
                          PortableServer::USE_SERVANT_MANAGER );
   policies[i++] = poa->create_servant_retention_policy(
                          PortableServer::NON_RETAIN );
   policies[i++] = poa->create_id_assignment_policy(
                          PortableServer::USER_ID );

   PortableServer::POA_var subpoa =
                   poa->create_POA( "lb_poa", mgr.in(), policies );

   MigratorImp mig;
   subpoa->set_servant_manager( mig._this() );


Python:
===============
#class declaration
class MigratorImp( PortableServer__POA.ServantLocator ):

# preinvoke snippet
   def preinvoke(self, oid, poa, op) :
      b = # get the real reference somehow
      raise PortableServer.ForwardRequest(b)

# set up the POA
   pol1 = [
     poa.create_request_processing_policy(
          PortableServer.USE_SERVANT_MANAGER ),
     poa.create_servant_retention_policy(
          PortableServer.NON_RETAIN ),
     poa.create_id_assignment_policy(
          PortableServer.USER_ID ) ]
   poa1 = poa.create_POA("lb_poa", mgr, pol1)
   mig = MigratorImp()
   poa1.set_servant_manager( mig._this() )

The C++ code works fine ( actually I haven't tested it with omniORB, but
with Orbix2000 ).  The Python server generates this trace message (at level
25)

omniORB: throw UNKNOWN from pyExceptions.cc:139
(MAYBE,UNKNOWN_SystemException)

And the client then gets this

Traceback (most recent call last):
  File "ping.py", line 16, in ?
    r = o1.ping()
  File "/opt/ilog/dev/j00128/consol/scripts/load/load_idl.py", line 49, in
ping
    return _omnipy.invoke(self, "ping", _0_DTLB.Pingable._d_ping, args)
omniORB.CORBA.UNKNOWN: Minor: UNKNOWN_SystemException, COMPLETED_MAYBE.

Has anyone implemented a ServantLocator in Python which raises a
ForwardRequest and get the right behavior?

Thanks,
Kendall