CORBA Naming Service in Lisp

The files in this directory provide a straightforward implementation of a CORBA Name Service in Lisp.

These files also serve to illustrate: some issues in starting up a persistent server.

Although the CORBA Naming service is the sanctioned CORBA method for inter-orb naming, its IDL and semantics can be complicated too learn and to use in simple applications. Unless you have an existing CORBA name service installed, you might find it easiest to use a more straightforward mechanism (see the discussion of naming in the main ORBLink documentation tree.

The detailed semantics of a CORBA naming service are discussed in any good book on CORBA. They will not be described here.

Starting up the naming service

In order to start up this naming service you must not yet have started a a listener. After loading orblink you should load the file naming-invoke.cl and evaluate (load-naming):

(in-package :user)
(require :orblink)
(load "naming-invoke.cl")
(load-naming)

This will define the class

orblink/naming:NamingContext

which implements the IDL interface

CosNaming::NamingContext

defined in the file CosNaming.idl.

You can instantiate an instance of

orblink/naming:NamingContext

via

(make-instance 'orblink/naming:NamingContext)

You can then publish and re-use this IOR however you want.

In many situations the naming service is used expressly to avoid, or at any rate to minimize the complexity of, publishing the IOR. In certain such situations it can be convenient for the IOR to be persistent, which means that the server will always listen on the same port and on the same host (with the same marker).

The function

(orblink/naming:start-nameserver)

will create an instance of orblink/naming:NamingContext [which, of course, is something different from the IDL compiler generated class COSNaming:NamingContext] whose IOR is persistent over invocations. In this case, this should be the first object published; normally you will want a single Lisp world dedicated to running the nameserver.

Any other ORBLink invocation can then get the IOR of this NamingContext by invoking the

(orblink/naming:nameservice-ior)

function with appropriate host keyword argument. The

(start-nameserver)

invocation can fail in two ways:

It will signal an error if a server has already been started on a same or different port in that Lisp world.
It will signal an error if a nameserver on the designated port of that host already exists.

The default port number is given by

orblink/naming:*default-naming-port*

It is worthwhile to study the code in naming-administration.cl as it illustrates the process of creating a persistent IOR.

Of course, the code in the other .cl files can be used to study the implementation of a nontrivial IDL interface.

Descriptions of files used in this directory

Here are the files used in this directory:

CosNaming.idl contains the IDL for the CORBA Services Name Service.
naming-invoke.cl is intended to be loaded by the user. It defines the orblink/naming package and the (user::load-naming) function.
naming.cl contains the implementation of the
```
CosNaming::NamingContext
```
IDL interface as the Lisp class named
```
orblink/naming:NamingContext
```
This Lisp class defines a single slot, entries, that holds an alist encoding the bindings managed by that naming context. This file contains implementations for all of the IDL-defined operations in the interface CosNaming::NamingContext.
naming-utility.cl contains helper functions that do the work of looking up names; the operation implementations just dispatch to appropriate helper functions. The only tricky aspect is that exactly the right exceptions must be signalled and a local namingcontext implementation (that is an instance of class orblink/naming:NamingContext, may contain bindings that point to proxies for the IDL interface CosNaming::NamingContext. Thus, the utility functions cannot normally be invoked iteratively.
naming-administration.cl contains functions that actually start a name service on a specified port. The invocation protocol is described above.
naming-accessors.cl contains accessors for managing the alist of entries.
binding-iterator.cl contains the implementation of the CosNaming::BindingIterator IDL interface. The interface is implemented by a Lisp class named orblink/naming:BindingIterator.