[rudder-users] Class definition

[Francois Armand]

On 25/03/2014 02:27, Chris wrote:
> [...]
>>> Another question is how to trigger rules based on the outcome of other
>>> rules.  Perhaps I haven't looked closely enough, but is this possible
>>> out of the box or does that require something custom to glue things
>>> together?
>> Do you have an example of what you need ? I'm not sure I understand what
>> you need here.
> I suppose it would map directly to something like 'classes => if_ok("no_problem")'.
> It would be different than what I explained above because it wouldn't be
> information you would want in inventory, and could change very quickly.
> So a simple example would be restarting a service based on file changes.
> As I understand it, a directive would need built in support to run
> something after a change.  I was wondering if there were a more free form way
> to define dependencies.


OK, I think I see what you want.
I fear that, as you said, you will have to build that logic
intra-technique, and it's typically what we do for restarting a service
when it's config file changed (for ex., see the openssh server
technique). And has technique are (or should be/were thought to be)
closed components, independant from each others, building cooperation
between them is for now ad-hoc, and can be fragile. 

But I believe I can help you nonetheless. As we thought that kind of
things should be simple and built-in, we start ncf ( http://www.ncf.io/
), an abstraction, component-based framework based on CFEngine, and it
is (starting to) be integrated with Rudder.

With ncf, you can do something like that:

    bundle agent ntp {
      methods:
        "package" usebundle  => package_install("ntp");
        "config"  usebundle  => file_from_template("ntp.conf", "/etc/ntp.conf");
        "reload"  usebundle  => service_restart("ntp"),
                  ifvarclass => "file_from_template__etc_ntp_conf_repaired";
        "running" usebundle  => service_ensure_running("ntp");
    }


the class "file_from_template__etc_ntp_conf_repaired" if named by
concention and automatically raised by "file_from_template" when needed.

Is this that kind of thing you want ?

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