[omniORB] resolve() and _remote_non_existent()

[Duncan Grisby]

On Wed, 2012-12-12 at 18:50 +0530, smitha smi wrote:

> Below is the sequence of calls i make.
> 
> (1) o_ObjRef = rootContext->resolve(name);
> 
> This call is success as it is not throwing any exception.

That call talks to omniNames and resolves the name to an object
reference. omniNames doesn't know or care whether the object reference
is valid.

> try {
> 
> ServerReady_var l_readyObjRef = ServerReady::_narrow(o_ObjRef);

That uses static knowledge to compare the expected interface with the
interface details stored in the object reference. In this case, it does
not need to do a remote call.

> // Note: _is_nil call does not result in IPC
> 
> if (l_readyObjRef->_is_nil())

_is_nil() never does a remote call. It is comparing the object reference
to nil, which is a purely local operation. An object reference is only
nil if it is nil. It has nothing to do with whether the object exists or
not.

[...]
> if(l_readyObjRef->_remote_non_existent())

You shouldn't call _remote_non_existent -- that is an internal omniORB
implementation detail. You should call _non_existent, which is the
standard method.

[...]
> catch (...)
> {
> printf("\n _remote_non_existent() threw an exception\n");
> }

[...]
> Result of execution of this code is : "_remote_non_existent() threw an
> exception"

If you catch CORBA::SystemException, you'll be able to call _name() on
it and you'll see what the exception was.

_non_existent contacts the server and asks if the object exists. It can
throw system exceptions like CORBA::TRANSIENT or CORBA::COMM_FAILURE if
the server cannot be contacted. If the server can be contacted but the
object does not exist, _non_existent will return true. omniORB's
internal _remote_non_existent will throw CORBA::OBJECT_NOT_EXIST.


> (a) What is the difference between resolve() and
> _remote_non_existent() ?

They are totally unrelated. resolve() is an operation on the naming
service that looks up a name. _non_existent is about checking the
existence of an object.

> (b) After successfully getting the object reference by calling
> resolve() , why show we make call to remote_non_existent() ?

You shouldn't call _remote_non_existent!  You could choose to call
_non_existent if you want to make an initial check for object existence.

[...]
> If Object was not existing, then resolve() it self should have thrown
> exception. but , it did not throw any exception Why?

resolve() looks up an object in the naming service. The naming service
doesn't care at all whether the object references it contains are valid
or not.

Regards,

Duncan.

-- 
 -- Duncan Grisby         --
  -- duncan at grisby.org     --
   -- http://www.grisby.org --