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DragonFly kernel List (threaded) for 2005-02
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Re: rc and smf

From: Dan Melomedman <dan@xxxxxxxxxxxxxxxx>
Date: Thu, 24 Feb 2005 15:50:54 -0500
Mail-followup-to: kernel@crater.dragonflybsd.org

Chris Pressey wrote:
> - Not everyone needs a fault-tolerant system.  Or rather, different
> people need different degrees of fault-tolerance.  Most people don't
> need telecom-level reliability.

I agree completely. Again, I was just trying to show why the feature is

> - Many daemons implement some form of supervision themselves.  Much of
> the 'djb regime' is not actually new, it just tries to commodify
> concepts such as supervision and daemonization at the operating system
> level, rather than having every program do it themselves.

Precisely. Many, or most services traditionally are not even written to
do it in the first place, doing it on the OS level is a very good thing.
It's an additional level of supervision, even if a service attempts to
supervise itself, like Apache. What's stopping the parent Apache service
from being killed or crashing?

> - Erlang's concurrency is typically much more fine-grained; most Erlang
> processes are not daemons in the usual sense (they only ever service
> each other rather than the outside world.)  The programming paradigm in
> this case is also different; because supervision guarantees have already
> been made, failure is "acceptable", and many processes are written in a
> "let it crash" style.  This simplifies error handling immensely in many
> cases, BUT it's most practical when working with lightweight processes
> (basically threads).  It's not nearly as effective a programming style
> when working with operating system processes.
> -Chris


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