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From Greg Wilkins <gr...@mortbay.com>
Subject Re: request for review: server/config discussion
Date Tue, 20 Jul 1999 22:57:56 GMT
Ben Laurie wrote:
> Much as I like the idea of notifying config changes, I think it is
> likely to lead to trouble. Here's the problem in a nutshell: either you
> notify in detail what the changes are, in which case we are looking at
> horrendous complexity and likely lots of interesting failure modes, or
> you just say "it's changed" in which case you only need a single module
> that requires a restart (canonical example: Apache listeners - these
> cannot change without a restart) and every change gives you a restart
> anyway.
> 
> I suppose its possible that there's some middle ground, but I'm afraid
> my imagination has failed me...

I think the middle ground is to allow detailed notifications, but not to 
expect modules to be able to handle them.

Just like a windowing system that might notify that a small region needs
to be redrawn, but a particular window decides that's all to difficult and
just redraws the entire window.

If there is going to be a "something has changed" notification mechanism,
then it is not too much extra effort to pass a list of names/nodes/whatevers
that are what have changed.  If the notification observer can't make sense
of the list, then it can drop it's bundle and restart as nicely as it knows
how.

I don't see this as horrendous complexity (but then I don't see it delivering
true dynamic reconfiguration in the first n releases either...).

cheers

-- 
Greg Wilkins<gregw@mortbay.com>          GB  Phone: +44-(0)171-4394045
Mort Bay Consulting Australia and UK.    Mbl Phone: +44-(0)7775534369
http://www.mortbay.com                   AU  Phone: +61-(0)299772395

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