FT — Harmful deprecation of LOCATE_FORWARD_PERM for Faut Tolerant CORBA

Earlier this year, the interop FTF deprecated the LOCATE_FORWARD_PERM
exception because of several reasons :

• it was badly specified
• it made the implementation of hash() difficult, and broke most of the
  existing ones.

It turns out that the Fault Tolerance specification published a little
earlier crucially requires a similar mechanism.
In normal life, most applications can rely on plain LOCATE_FORWARD because
there is no reason to expect the death of the originally pointed component.
In the case of Fault Tolerant CORBA, this is entirely different: it is
precisely when we issue a LOCATE_FORWARD_PERM that we know for sure that
the original component is dead, and might never return. If all the backup
profiles of an IOR enjoy the same death, all hope is gone.

This means that without a mechanism similar to LOCATE_FORWARD_PERM, the
Fault Tolerant CORBA spec cannot address the requirements of real
fault-tolerant systems.

This is why the Fault-Tolerant CORBA FTF would like to see LOCATE_FORWARD_PERM
re-introduced in some way. Here are a few ideas that might help :

Issue of scope:
The scope of LOCATE_FORWARD_PERM is ORB lifetime.

Issue of hash() :
Let us be reminded that the Fault-Tolerant CORBA spec defines teh concept of
an Interoperable Object Group Reference (IOGR). The IOGR contains a specific
profile that contains a group identifier.

• When an ORB receives and IOGR, it should compute the value of hash() based
  on the GroupID contained in the IOGR, and performs LOCATE_FORWARD_PERMs if
  requested.
• When an ORB receives a normal IOR (i.e. an IOR lacking a group profile) it
  computes hash() in the customary way, and doesn't have to respond to
  LOCATE_FORWARD_PERMs.

see below