Puppet users - Oct 2010 - how can i determinate from one class if another class applied?

Hello everybody!
How can i determinate from one class if another class applied to the
this node?

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On Fri, Oct 15, 2010 at 12:40:57AM -0700, walexey wrote:
> Hello everybody!
> How can i determinate from one class if another class applied to the
> this node?
Use the defined() function.

-- 
Bruce

What would Edward Woodward do?

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On 10/15/2010 09:40 AM, walexey wrote:
> Hello everybody!
> How can i determinate from one class if another class applied to the
> this node?
> 
You can use the defined() function.

if defined(Class[my_class]) {
 ...
}

YOU SHOULD NOT DO THAT, though. There are problems, because puppet may
include classes in a different order in each run. See the details in
http://docs.puppetlabs.com/references/stable/function.html#defined

If the class you test for belongs to an earlier stage (in 2.6.0+), this
problem may be sidestepped. I''m not sure if that''s how that
works, though.

HTH,
Felix

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What you''ll probably want is the tagged() function, not defined().

Someone correct me if I am wrong, but defined() is useful for checking
if types or classes exist ("are known about") but does not check
whether a class is DECLARED - there''s a difference. Note the
documentation sentence "This is useful for checking whether a class is
defined and only including it if it is".

So if you have a master imports a manifest with a class called "foo"
then:

if defined(foo) == true (always)
if tagged(foo) == true (only if your node has ''include foo'')

What Felix says about the defined() function I beleive only applies to
checking for specific resources, which depends on the specific parse
order (and all you have to do is run ''puppetd --noop --test --
evaltrace'' to see the parse order changes ALL the time).

On Oct 15, 8:40 am, walexey <wale...@gmail.com>
wrote:
> Hello everybody!
> How can i determinate from one class if another class applied to the
> this node?
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On Fri, Oct 15, 2010 at 01:04:29AM -0700, luke.bigum
wrote:
> Someone correct me if I am wrong, but defined() is useful for checking
> if types or classes exist ("are known about") but does not check
> whether a class is DECLARED - there''s a difference. Note the
> documentation sentence "This is useful for checking whether a class is
> defined and only including it if it is".
You''re not wrong.  That said, I''d actually advice the OP
against trying
this kind of thing.  Generally, I find specific class dependencies are
something to avoid.  The only place I tolerate them is in "role"
classes, which is where I usually set up any dependencies between
modules that are required, and there I don''t need to use defined() or
tagged() to check them, because I know precisely which classes have been
included.

Every time you add a dependency to a specific class, you cause problems
for the person who finds a need to creat a new class that inherits from
it.  That person will often be you and kicking yourself is not
rewarding.  Looking at my manifests and modules, the *only* places I
have a dependency on a named class is in my site::role classes and in
the samba::packages class where the named classes are internal to the
samba module and contain collections of packages (and their
dependencies) relevant to specific versions of Samba.

-- 
Bruce

Explota!: miles de lemmings no pueden estar equivocados.

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I have following problem:
defined class ldap-client, which install and configure ldap on _all_
nodes. there is file[/etc/nsswitch.conf]. it add ''ldap'' to
nsswitch.conf
defined class winbind, which install and configure winbind on _some_
nodes. and it need also to change nsswitch.conf, adding
''winbind''
there.

i can''t imaging something better than add

       if tagged(winbind) {
                $winbind = ''winbind''
        } else {
                $winbind = ''''
        }
in ldap-client class

and add
passwd:     files <%= winbind %> ldap
to nsswithch.conf template.

can you show me the right way?

btw, my solution don''t work. tagged(winbind) in ldap-client return
always false, but winbind class runs ok.

On 15 окт, 13:40, Bruce Richardson <itsbr...@workshy.org>
wrote:
> On Fri, Oct 15, 2010 at 01:04:29AM -0700, luke.bigum wrote:
> > Someone correct me if I am wrong, but defined() is useful for checking
> > if types or classes exist ("are known about") but does not
check
> > whether a class is DECLARED - there''s a difference. Note the
> > documentation sentence "This is useful for checking whether a
class is
> > defined and only including it if it is".
>
> You''re not wrong.  That said, I''d actually advice the OP
against trying
> this kind of thing.  Generally, I find specific class dependencies are
> something to avoid.  The only place I tolerate them is in "role"
> classes, which is where I usually set up any dependencies between
> modules that are required, and there I don''t need to use defined()
or
> tagged() to check them, because I know precisely which classes have been
> included.
>
> Every time you add a dependency to a specific class, you cause problems
> for the person who finds a need to creat a new class that inherits from
> it.  That person will often be you and kicking yourself is not
> rewarding.  Looking at my manifests and modules, the *only* places I
> have a dependency on a named class is in my site::role classes and in
> the samba::packages class where the named classes are internal to the
> samba module and contain collections of packages (and their
> dependencies) relevant to specific versions of Samba.
>
> --
> Bruce
>
> Explota!: miles de lemmings no pueden estar equivocados.
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On Fri, Oct 15, 2010 at 07:06:52AM -0700, walexey wrote:
> i can''t imaging something better than add
> 
>        if tagged(winbind) {
>                 $winbind = ''winbind''
>         } else {
>                 $winbind = ''''
>         }
> in ldap-client class
> 
> and add
> passwd:     files <%= winbind %> ldap
> to nsswithch.conf template.
> 
> can you show me the right way?
> 
There is more than one way to do this.

A simple way would be to use a variable to indicate whether you want
winbind integration.  Then anything that needs to know whether winbind
is active can just check the variable - including the piece of code
where you decide whether nor not to include the winbind class/module.

The canonical Puppet way of dealing with it is to write a custom
resource to manage nsswitch.conf.  How good are your ruby skills?

I have found a way to abuse virtual define-based resources so that you
can effectively write your own custom resources in the Puppet DSL,
rather than using Ruby, which I consider to be overkill for a case as
simple as this.  I will write it up when I have a moment, this weekend.
Meanwhile, if you aren''t great at Ruby, I suggest the simple method I
described first.


node "host.on.which.I.want.winbind.active" {
	$winbind_integration = true
	include site::role::server
}

class site::role::server {
	if $winbind_integration {
		include samba::winbind
	}
}


---- nsswitch.conf.erb ----

passwd: files <% if winbind_integration == true %>winbind<% end %>
ldap


---- nsswitch.conf.erb ----

It''s not the most elegant solution (not the last bit, anyway) but it
works and if you can''t trust yourself to set the right variables in the
correct hosts, who can you trust?

-- 
Bruce

Bitterly it mathinketh me, that I spent mine wholle lyf in the lists
against the ignorant.  -- Roger Bacon, "Doctor Mirabilis"

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On 10/15/2010 05:40 PM, Bruce Richardson wrote:
> On Fri, Oct 15, 2010 at 07:06:52AM -0700, walexey wrote:
>> i can''t imaging something better than add
>>
>>        if tagged(winbind) {
>>                 $winbind = ''winbind''
>>         } else {
>>                 $winbind = ''''
>>         }
>> in ldap-client class
>>
>> and add
>> passwd:     files <%= winbind %> ldap
>> to nsswithch.conf template.
>>
>> can you show me the right way?
>>
> 
> There is more than one way to do this.
So true... ;-)

If there are only those two flavors of nsswitch.conf files in your
network (or very few more), you might put it in a class of its own:

class nsswitch_conf { file { "/etc/nsswitch.conf": content =>
"..." } }

Then add the proper passwd line in a subclass:

class nsswitch_conf_winbind inherits nsswitch_conf {
  File["/etc/nsswitch.conf"] {
    content => "...\npasswd: files windbind ldap\n..."
  }
}

This approach is limited, but you could as well use your template in the
nsswitch_conf class and set different variables in the subclass.
(Remember to still use the override as sketched above, simply setting
variables will do no good in a subclass). That still saves you from the
scoping and order fuss.

Each of your nodes will include nsswitch_conf per default, an in your
ldap client class, you will additionally include nsswitch_conf_winbind.

Regards,
Felix

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