As far as I understand this is not really possible. This is because you don’t
have control over the order of compilation of resources into the catalog. The
compiler first evaluates all classes then moves on and eventually has a step
that evaluates all collections and so on until the catalog is complete.
You can work around this by ‘bumping scope’ which means you need to get the
evaluation of the getparam() to happen after the collection has occurred and
the resources are in the catalog. This is essentially what is happening in
your define example.
By bumping scope I mean that you need to do any evaluations in a define that is
‘one scope’ more then then where then resources will be added to the catalog.
My scope I mean the order that the compiler will evaluate things.
So when you have a collection in a class the actual collection will happen
after all classes are evaluated by the initial pass by the compiler hence why
you see the behavior you do. So if you create a define, use it in the class
and have that define evaluate the getparam() then it /might/ work. Of course
you won’t be able to get to those values in your class (because its already
been evaluated). I say /might/ work because you can’t be sure that the define
you create and the defined type you collected will happen in the right order ie
that the collection will happen first. To be sure you can create a second
define and use that in the first define and move the evaluation to the new
second define. This is why I call this ‘bumping scope’. At this point the
evaluation will happen after the collection’s defined types are in the catalog
and getparam() will work. This get fun when defines make use of defines and
the other defines need to reference these 2nd level (or 3rd level) defines.
You can keep adding defines to get things to work.
Now this looks ugly and is and I feel bad that I’ve done this but it works well
and has predictable results.
Finally the only way I think this can be fixed is it puppet went to a multipass
compiler that would ‘reevaluate’ resources if evaluations occurred that
reference those resources or their parameters. This would slow down
performance quite and bit and have almost no benefit for most people.
From: desertkun
Sent: Monday, January 8, 2018 9:10 AM
To: Puppet Users
Subject: [Puppet Users] Puppet ordering: ensure exported resource to
beevaluated BEFORE classes
I would like to export "location" information from one node to another. And
stuck with that problem for weeks now.
In order to achieve that, I use exported resources. Here's the simplified idea:
define location ($host) {
notify {"Location being defined ${title} -> ${host}": }
}
# export the location
node 'a' {
@@location { "mysql-server":
host => $hostname
}
}
node 'b' {
# later import it on another node
Location <<| title == "mysql-server" |>>
# extract the data
$mysql_server_host = getparam(Location["mysql-server"], "host")
}
Pretty much I use exported resources as some sort of exported "facts". The
problem with that, that puppet cannot realize the Location inside the classes
or at node level scope, but does it just fine within resources:
DOES NOT WORK:
class class_example() {
# something like realize Location["mysql-server"] doesn't even compile
Location <<| title == "mysql-server" |>>
$mysql_server_host = getparam(Location["mysql-server"], "host")
notify {"Example in class: ${mysql_server_host}": }
}
node 'b' {
class { class_example: }
}
Yields: "Notice: Example in class:"
WORKS JUST FINE:
define resource_example() {
Location <<| title == "mysql-server" |>>
$mysql_server_host = getparam(Location["mysql-server"], "host")
notify {"Example in resource: ${mysql_server_host}": }
}
Yields "Notice: Example in resource: hostname-x"
The problem with that, I my guess, the puppet evaluates stuff in two stages,
classes first, and then resources, including exported resources. What is also
interesting, that notify I've put for debug yields like that:
Example in class:
Example in resource: hostname-x
Location being defined mysql-server -> hostname-x
If I do "require => Location["mysql-server"]" for the resource, the ordering
shows right, but result is the same:
Example in class:
Location being defined mysql-server -> hostname-x
Example in resource: hostname-x
The question is, how do I enforce puppet to evaluate class AFTER exported
resource? Would "stages" help me out here? As a workaround, I have to wrap
classes in a single-instance resources.
Thank you very much in advance.
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