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From Ben Laurie <>
Subject Re: request for review: server/config discussion
Date Wed, 21 Jul 1999 12:44:42 GMT
Greg Wilkins wrote:
> 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...).

Actually, I expected the complexity to be in the listeners, not the
notification mechanism, leading to the same kind of cockup that causes
bits of windows to not display the right thing, only about a zillion
times harder to spot...




"My grandfather once told me that there are two kinds of people: those
who work and those who take the credit. He told me to try to be in the
first group; there was less competition there."
     - Indira Gandhi

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