multiple CORBA servers on one machine

This isn't really a LispWorks question, but it is about something
implemented in LW...

I have a little server I wrote which allows a lisp application to
handle requests from a client via CORBA.  All it really does is passes
arrays of strings around with a single call, which it then treats as
command lines - it should really have been written on top of plain
sockets, not CORBA.  The server writes its IOR into a secret file in
the user's home directory, which the client then uses for getting in
touch with it.

I never intended this thing to actually get used, but in the nature of
things it's become central to our existence because it allows shell
scripts and makefiles to get Lisp to do things completely trivially.

The problem is that there doesn't seem to be a way for multiple
servers to coexist on one machine - so on our Linux `build server'
machine you can't have two people doing things at once.  This seems to
be because the servers try and open the same port at some sub-CORBA
level.  I presume (or hope, anyway) that CORBA has some answer to this
kind of issue, but my knowledge of CORBA is tiny: does anyone know
what how to do this so I can be lazy and not read huge manuals
(pointers to the manual section would be OK - we have the CORBA
specs...)?

Thanks

--tim

PS the way we start the server now is this:


(defun start-clc-server (&key (threads 1)
                              (wrapper nil))
  ;; See above for WRAPPER
  (unless (= threads 1)
    (error "No multithreaded support yet"))
  (let* ((ior-file (ior-file-name))
         (orb (ensure-orb)) ;calls op:orb_init if need be
         (poa (op:resolve_initial_references orb "RootPOA"))
         (manager (op:the_poamanager poa))
         (ob (op:narrow
              'org.tfeb.corba-modules/clc:server
              (op:servant_to_reference
               poa
               (make-instance 'clc-servant
                              :wrapper wrapper))))
         (ior (op:object_to_string orb ob)))
    (op:activate manager)
    (with-open-file (out ior-file
                         :direction :output
                         :if-exists :supersede)
      (format out "~A~%" ior))
    (values ob manager)))

Re: multiple CORBA servers on one machine

Tim Bradshaw wrote:
> machine you can't have two people doing things at once.  This seems to
> be because the servers try and open the same port at some sub-CORBA
> level.  I presume (or hope, anyway) that CORBA has some answer to this

If you really want to instantiate different SERVERS,
i.e. different (heavy weight) processes,
try to change *CORBA:POA-SERVICE-PORT*
BEFORE you load any CORBA related LW packages.

I was able to use this hack on Win98
spawning two instances of LWW4.2
(and of course performing some communication).

To Xanalys:
Please,
tell us if this is the PREFERRED way
to change the port number ...

If you need to support different SERVICES within the same server,
you will have to dive into the OMG documentation
on POAs and its activation schemes.
LW claims 2.2 POA support:
http://www.omg.org/cgi-bin/doc?formal/98-07-01.pdf.gz

========================================================================

               Universitaet Hamburg
               Fachbereich Informatik

Ralf Bachmann  Angewandte und sozialorientierte Informatik (ASI)
               Vogt-Koelln-Strasse 30
               D-22527 Hamburg

         Raum  D 227
      Telefon  +49 40 42883 2316
      Telefax  +49 40 42883 2311
        Email  bachmann@informatik.uni-hamburg.de
          WWW 
http://asi-www.informatik.uni-hamburg.de/personen/bachmann

Re: multiple CORBA servers on one machine

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Re: multiple CORBA servers on one machine

* Ralf Bachmann wrote:

> If you really want to instantiate different SERVERS,
> i.e. different (heavy weight) processes,
> try to change *CORBA:POA-SERVICE-PORT*
> BEFORE you load any CORBA related LW packages.

Yes, that is what I want to do. This seems to work (on linux, anyway),
though it terrifies me...  What I do is, when Lisp starts (this is a
dumped image with corba loaded as well as my clc thing), I do this:

(define-action "Initialize LispWorks Tools" 
               "Start CLC server"
               #'(lambda (&rest junk)
                   (declare (ignore junk))
                   (mp:process-run-function 
                    "Starting CLC" ()
                    #'(lambda ()
                        ;; try to select an unused port, so more than
                        ;; one person can run a server on a machine.
                        ;; It is not at all clear to me if this is
                        ;; right or safe!
                        (loop with stream 
                              for port from corba:*poa-service-port*
                              repeat 100 ;?
                              while
                              (unwind-protect
                                  (not (null (setf stream
                                                   (comm:open-tcp-stream
                                                    "localhost" port))))
                                (when stream (close stream)))
                              finally
                              (setf corba:*poa-service-port* port))
                        (unless (org.tfeb.clc.server:probe-clc-server)
                          (org.tfeb.clc.server:start-clc-server
                           :wrapper #'org.tfeb.clc.hax:wrapper))))))

This is mildly terrifying, but it works (it's not clear if it should
be safe to blindly open connections to possible other servers...).  Of
course, now I have the whole mechanism to select a port by repeated
probing I could just as well write the whole thing in far less code by
simply having a little process which listens for command lines on a
TCP port...

--tim

Re: multiple CORBA servers on one machine

>>>>> "Tim" == Tim Bradshaw <tfb@cley.com> writes:

....

    Tim> This is mildly terrifying, but it works (it's not clear if it
    Tim> should be safe to blindly open connections to possible other
    Tim> servers...).  Of course, now I have the whole mechanism to
    Tim> select a port by repeated probing I could just as well write
    Tim> the whole thing in far less code by simply having a little
    Tim> process which listens for command lines on a TCP port...

Hi,

Actually OS's will give you unused port numbers for sockets if you ask
them nicely so you don't need this probing loop. I gather than the
only way of getting at this functionality via the LW ORB at the moment
is to bind that unsupported special to NIL, but I expect that there
will be a way of getting at this functionality via the command line
arg in due course.

__Jason

Re: multiple CORBA servers on one machine

* Jason Trenouth wrote:
>>>>>> "Tim" == Tim Bradshaw <tfb@cley.com> writes:
> ...
> Actually OS's will give you unused port numbers for sockets if you ask
> them nicely so you don't need this probing loop. I gather than the
> only way of getting at this functionality via the LW ORB at the moment
> is to bind that unsupported special to NIL, but I expect that there
> will be a way of getting at this functionality via the command line
> arg in due course.

I don't think this works, on Linux anyway (not the
giving-of-free-ports-by-the-OS, which obviously does, but the binding
of CORBA:*POA-SERVICE-PORT* to NIL).

I do something which is essentially:

  set CORBA:*POA-SERVICE-PORT* to NIL
  initialize the ORB with op:orb_init with null argv
  call op:resolve_initial_references on it.

This last call hangs for a very long time (many seconds) and then
signals some corba exception.

If I do my repeated-probe thing (which is infinitely more hacky) all
this code works.

--tim

Re: multiple CORBA servers on one machine

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