Forum: CFEngine Help
Subject: Re: CFEngine Help: Re: controlling redhat-style startup services via
chkconfig
Author: matt_garman
Link to topic: https://cfengine.com/forum/read.php?3,24170,24171#msg-24171
Jesse Becker Wrote:
-------------------------------------------------------
> You can't do this (easily) because vars: promises
> are processed before
> classes: promises. Thus, but the time you have
> defined the "needs_ntp"
> class, it's too late--you've already processed the
> vars: definitions.
>
> You have at least two possible workarounds:
>
> 1) use hard classes in vars:. This works because
> hard classes are
> defined before the processing of the promises.
>
> 2) do some trickery with isvariable() when
> defining classes to create
> what I call a "guard" class, then use that to
> define a variable in the
> next pass through the bundle. It's complicated
> and ugly.
Regarding (2), I don't really understand what you're saying, but I'll take your
word that it's "complicated and ugly" and therefore not something I want to
pursue. :)
So, somewhat for posterity, what you mean by (1) is this:
vars:
# can't use soft class "need_ntp" here, because class promises
# are determined after var promises.
linux|cfengine_3:: "service" slist => { "ntpd", "named" };
!(linux|cfengine_3):: "service" slist => { "named" };
And that does exactly what I want, at least the outcome is what I want.
So, now: what is the rationale behind processing vars: promises before classes:
promises?
And secondly, is there an overall cleaner, simpler and easily-maintainable
approach to the problem I'm trying to solve? That is, all my servers have some
common subset of services that I want to have run at startup. But then there
are a handful of servers that additionally need service1, another handful that
need service2, and another small handful that need service3.
I guess I could have a promise for all the common services, and then a
per-service promise for each special case. But as a programmer, that feels a
lot like code duplication.
Any hints or advice? I can't imagine this being an uncommon scenario.
Thanks!
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