Re: Glade :- he distributed Annex

[Ole-Hjalmar Kristensen <oleh@vlinux.voxelvision.no>]

dennison@telepath.com (Ted Dennison) writes:

> Toshitaka Kumano <kumano@cl.cilas.net> wrote in message news:<mailman.1017942482.19817.comp.lang.ada@ada.eu.org>...
> > In other malicious words, I consider Glade by itself could not be
> > used for practical, fault tolerant or real-time (deterministic response)
> > application. This can be "restriction" in your application domain.
> 
> Considering that TCP itself can't be used for that kind of real-time
> application (and IP itself can't either, except under certian
> circumstances), that's a pretty safe statement.
> 
> 
> -- 
> T.E.D.
> Home     -  mailto:dennison@telepath.com (Yahoo: Ted_Dennison)
> Homepage -  http://www.telepath.com/dennison/Ted/TED.html

On the other hand UDP/IP is perfectly good enough to run fault tolerant 
*soft* real time systems in a workstation cluster. In other words, good enough 
for a telephone company, but don't try running your engine controller on it.

For building a fault tolerant networked application, you don't really need a 
reliable transport protocol, what you need is a reliable indication of a node 
or network error.

A "reliable" transport protocol usually only gets in your way by insisting 
that everything is fine until it at last admits that it cannot deliver 
your message. Then you have to handle the error yourself anyway.

Having spent the last years working on such a beast in C++ (a soft
real-time, fault-tolerant, scalable RDBMS), it would be very
interesting to see if Glade could be used for such applications. A
quick guesstimate tells me that there would be great savings both in
terms of readability, maintainablity, and code volume (at least a
factor of 2 for some modules) by using Ada threads and Glade instead
of the homegrown RPC-like mechanism and extremely primitive (but fast)
thread system we used.

Btw., I've been trying to get Glade to run under Windows 2000, but when running 
gnatdist, gcc complains that the distribution feature is not supported.
This is Glade 3.14p, with ditto GNAT. I used Cygwin to build Glade, 
apparently with no errors.

Any suggestions?