Re: Configuration services

[David Miller <dave@frop.net>]

Laurent spoke thusly:
> > I want to be able to have other services depend on it.
> > (cut)
> > I also have a ./finish script that undoes all the configuration
> 
>  ... and if a stray signal happens to kill your shell, your "service"
> will be deconfigured and reconfigured.
>  The supervisor is there to ensure a process remains up no matter what;
> it's suppoed to maintain a *process*, not a *state*. The only state it
> can guarantee is 'want up', i.e. if the process ever goes down, you can
> be sure it will be run again.
> 
>  You are not the first to want to use the daemontools/runit pattern as
> a dependency manager, implementing a wider notion of 'service' than it
> really does. As far as I can tell, this is not a very good idea - it
> can be made to work, but it's generally shaky and unsatisfying. As a
> rule of thumb, whenever you have a loop in your run script, you are
> probably abusing the pattern.

Thanks for the good post.  It does seem like I am fitting a square peg in a round hole, so I wanted to make sure that I was not missing something.  And apparently I am not.  A few pages on Gerrit's site made me think that runit could be used in this way.  Quoting Gerrit from http://smarden.org/pape/djb/daemontools/noinit.html :

"Having the above design in mind, why not think about eth0 as a service? Let a supervisor garantee the state of eth0, take it like any other service."

I wonder if Gerrit can clarify what he meant by that.

runit already has some notion of states as opposed to processes,  it can use a ./check script to decide whether a service is "ready". I guess my point is that runit is very close to being able to be used in this manner but as you say it is a bit akward.

I am considering writing a shell script I can call from dependent services instead of using 'sv check'. But I am not sure if my while loop is sufficiently abominable to necessitate the effort. 

Thanks for the input everyone!
-- 
David Miller dave@frop.net http://dave.frop.net/