Re: Distributed Ada, robustness etc.

[Stephen Leake <stephen_leake@acm.org>]

"Dr. Adrian Wrigley" <amtw@linuxchip.demon.co.uk.uk.uk> writes:

> On Wed, 31 May 2006 07:49:20 +0200, Ludovic Brenta wrote:
>
>> I don't have anything useful to tell you, but please keep posting
>> here; I find this quite interesting.  Indeed, you seem to be at the
>> forefront of distributed Ada technology :)
>
> Thanks for the encouragement!

I also don't have much to contribute, but find this interesting.

> <snip>
>
> I do now try to call unregister when a partition terminates,
> using another mechanism.  But this doesn't quite match the
> needs, and can't be used in all circumstances.  And it's
> more complicated :(   If a partition is aborted, the only
> way the code can find out is by attempting a call and watching
> it fail.  This may be a weakness in the Annex E.

"abort" is a really nasty way to end a program. As you have seen, the
program can't do much in the way of cleaning up after itself.

In my systems, I always have some sort of "terminate" signal or
rendezvous to every component, and ensure that is issued/called for
_every_ error condition that results in termination.

Sometimes this means the component must poll for the terminate signal,
even though otherwise it doesn't need to poll for anything.

Yes, it is more complicated. But that's because shutting down any real
system _is_ complicated!

I don't think this is a "weakness" in Annex E; it's just reality.

-- 
-- Stephe