New Scope > 2.7

[Douglas Garstang]

So...

I was just reading the new puppet scoping documentation at
http://docs.puppetlabs.com/guides/scope_and_puppet.html.

I don't get it. If I have this...

class web_server {
include common
include webserver
$my_role = "web_server"
}

Can I access the $my_role variable in the webserver class?

Doug.

[llowder]

 
If you use: $web_server::my_role

 

Doug.

[Douglas Garstang]

This seems completely screwed to me. What if your in a general class,
one not necessarily related to the function of a web server (but still
included from a web server), and you need to access the role?

Doug.

[llowder]

Then use the fully qualified variable name as I mentioned in my last post.

 

Doug.

[Douglas Garstang]

What if the class I am in doesn't KNOW that the parent is $web_server ...?

Doug.

[Denmat]

What if you've declared my_role in several classes? This provides certainty. Alternatively you could make a fact that has the value you want of my_role and reference that in the top scope $::my_role.

[Dan White]

It is called: "Making an honest attempt to help you avoid shooting your own toes off".

By forcing you to specifically reference the class name along with the variable name (that includes the top scope $::foo), it saves you extensive grief down the road when you eventually end up with the same variable name in multiple classes.

Or would you rather have to track all the variable names in all the classes you use (the ones you write yourself along with ones you pull from places like the Puppet Forge) to ensure unique variable names ?

[Mark Roggenkamp]

You may want to consider making whatever needs $my_role into a define or class that can be used in another module. Then make a module to contain roles. These roles would be classes (since puppet has no role resources type like this) that include relevant defines/classes from other modules. I've found for my use cases composing things that way works a bit better, though of course YMMV.

Regards,

Mark

[James Sweeny]

Parameterized classes were also made for this issue, but I don't recommend going that route if you have several levels of classes being included before you have to use the variable.

You might find it worthwhile to set $my_role in Hiera, and provide a sane default within the webserver class.

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