puppet hash iteration – Replacing create_resources() with Hash Iteration in Puppet

configuration-managementpuppetruby

We're migrating from Puppet 2 to 5. It seems the scoping is a little different. Before, when using create_resources() with a hiera_hash and a default hash, variables from within the calling script were available to the ERB, but now they don't seem to be. For example, I could set $a = 'hello world' in the calling script right before create_resources(), and then within my ERB, I could simply reference $a and get back hello world. That doesn't seem to be the case now.

So the idea is to abandon create_resources() and use Puppet 5's each function on the hiera_hash just creating a new file within the loop. However, I'm having trouble merging the default values to each hash element. I'm not able to redeclare variables, so I can't do a merge within the loop it seems.

Here's an example of what I'm trying to do:

Data.file1.yaml

my::data:
  element_a:
    fname: 'Brian'
    lname: 'Detweiler'
  element_b:
    fname: 'Joe'
    lname: 'Schmoe'

Data.default.yaml

my::defaults
  mname: 'M.'

Before I would pull both of those in as hiera_hashs and do create_resources('my::template::script', $names, $names_default) and I would end up with the expected merges:

'element_a' => { fname => 'Brian', lname => 'Detweiler', mname => 'M.'},
'element_b' => { fname => 'Joe', lname => 'Schmoe', mname => 'M.'}

Now I want to do

$names.each | String $key, Hash $value | {
  $merged_hash_val = $names_default + $value
  file {
    # ... create file with $merged_hash_val in here
  }
}

But since variables are immutable, I can't reassign values. Is there a way around this?

Best Answer

Variables are still accessible to the template. I am concerned that there is something else going on there. You might not want to change your create_resources() usage if you address that.

See: https://puppet.com/docs/puppet/5.5/lang_template_erb.html#accessing-puppet-variables

Related Solutions

Puppet: Checking sets of variables

As @Zoredache mentioned, there is no loop in Puppet. But you can get around this by using a definition, something like this:

define show_ip {
    $inf = "ipaddress_${name}"
    $ip = inline_template('<%= scope.lookupvar(inf) %>')

    if $ip =~ /192\.168\.3.*/ {
        notify {"Found IP $ip": }
    }
}

$ifs = split($interfaces, ',')

show_ip { $ifs: }

Belows is the output when directly calling:

# puppet manifests/defines/net.pp 
warning: Implicit invocation of 'puppet apply' by passing files (or flags) directly
to 'puppet' is deprecated, and will be removed in the 2.8 series.  Please
invoke 'puppet apply' directly in the future.

notice: Found IP 192.168.3.118
notice: /Stage[main]//Show_ip[eth1]/Notify[Found IP 192.168.3.118]/message: defined 'message' as 'Found IP 192.168.3.118'
notice: Finished catalog run in 0.07 seconds

Source: https://blog.kumina.nl/tag/puppet-tips-and-tricks/

Set sysctl.conf parameters with Puppet

Specific answer: Immediately speaking, you're calling sysctl::value, but value isn't declared in your sysctl class. See this example that uses a sysctl::conf declaration. Without the define value, there is no sysctl::value subclass for you to call.

General answer and guidance: The Augeas construct (see also its type reference documentation) that is part of current versions of Puppet allows maintaining lines in a configuration file and even respects context, so it can manage files such as a git configuration. The example below is both to demonstrate functionality and to point you to a great reference collection of Puppet configs -- the live configuration store for Wikipedia servers.

[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
    ignorecase = true
[remote "origin"]
    fetch = +refs/heads/*:refs/remotes/origin/*
    url = https://gerrit.wikimedia.org/r/p/operations/puppet
[branch "production"]
    remote = origin
    merge = refs/heads/production

One simple example from the above configuration documentation would be this:

augeas { "sshd_config":
 context => "/files/etc/ssh/sshd_config",
  changes => [
    "set PermitRootLogin no",
  ],
}

So, if you want to manage your /etc/sysctl.conf, enter the following:

augeas { "sysctl":
 context => "/files/etc/sysctl.conf",
  changes => [
    "set kernel.sysrq = 0",
    #and whatever other lines are interesting to you
  ],
}

The Augeas example also has a construct for a sysctl class based on Augeus that is similar to what you posted in your question, so that may also shed some light.

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