On 11/7/07, Christine Tran <Christine.Tran at sun.com> wrote:
> Peter Tribble wrote:
> > I've been asked to create a setup in which there are several instances
> > of an application, with one and only one running at a time.
>
> There is a dependency type that sounds just like the job for this
> situation: exclude_all. The dependency is satisfied when !{service},
> man smf(5) for more. Never seen this used, so not sure what the framers
> intended.
Hm. Looks like it could help - simply make each service exclude all the others.
I'll have to try this - it could help with the "there can be only one" part
of the requirement. At least, it provides a mechanism to enforce it
rather than relying on users being cooperative.
Without actually trying it, it doesn't help ensure that one of the services
is running; nor does it help transition the active service from one service
to another.
Another problem that's just occurred to me is that adding another instance
means I have to update the dependencies of all the other members of the
group.
> The problematic thing I see is that the dependency is on service, and
> you are working with instances. Unless you do have properties that are
> inherited from service to instance, is it possible to make sendmail,
> postfix, qmail, exim all different *services*, instead of smtp:instance?
For my case, I can define them how I want, so that's not a problem.
(As a general comment, I consider instances to be separate services,
with the service/instance demarcation being a helpful way of showing
how service are related. I'm aware that SMF reads rather more into the
relationship than that...)
> Just my thoughts on a hack, would love to hear how you make out after
> you're done.
Thanks for the hint.
--
-Peter Tribble
http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/
