Appending a key to the top of an array - puppet

Question

I have some hiera not unlike the following (I know this is invalid hiera with two keys... bare with me):
an::example::rule_files:
my_rules:
groups:
- name: my_rules
rules:
- alert: highCPU
expr: CPU > 90
for: 5m
annotations:
summary: "CPU is too high"
description: "CPU should be less than 90"
someone_elses_rules:
groups:
- name: someone_elses_rules
rules:
- alert: highCPU
expr: CPU > 70
for: 5m
annotations:
summary: "CPU is too high"
description: "CPU should be less than 70 on someone else's system"
I'm trying to turn this into a yaml file (the key is the filename). Now I know this is invalid hiera and I can remove the groups key to get this working (exactly what I've done), however when I try to reinsert it into the array, I can't get the formatting right. Here's the puppet code I'm using:
$alert_files = hiera('an::example::rule_files'),
$alert_files.each | String $alerts_file_name, Array $alert_config_pre | {
$prefix = [ "groups:" ]
$alert_config = $prefix + $alert_config_pre
file { "/etc/prometheus/${alerts_file_name}.rules":
ensure => file,
content => $alert_config.to_yaml,
}
}
Here's what I want:
cat /etc/prometheus/my_rules.rules
---
groups:
- name: my_rules
rules:
- alert: highCPU
expr: CPU > 90
for: 5m
annotations:
summary: CPU is too high
description: CPU should be less than 90
and here's what I get:
---
- 'groups:'
- name: my_rules
rules:
- alert: highCPU
expr: CPU > 90
for: 5m
annotations:
summary: CPU is too high
description: CPU should be less than 90
Any help would be massively appreciated. I feel like this should be simple but I've not really made any progress (I can't even remove the quotes from the word groups). If this is possible in either hiera or puppet (perhaps I've defined the hiera wrong) then great; any progress I can make in any way will be really appreciated.

Answer 1

This ...
$alert_files = hiera('an::example::rule_files'),
$alert_files.each | String $alerts_file_name, Array $alert_config_pre | {
... depends on the data associated with key an::example::rule_files to be a Hash with String keys and Array values. In the YAML presented at the top of the question, that item is instead a hash with String keys and Hash values. Inasmuch as the data seem to match the wanted file content, the problem seems to be not with the YAML (except for the inconsistent indentation), but rather with the Puppet code.
To work as you appear to want with the data you want, the Puppet code might look more like so:
$alert_files = lookup('an::example::rule_files'),
$alert_files.each |String $alerts_file_name, Hash $alert_config| {
file { "/etc/prometheus/${alerts_file_name}.rules":
ensure => 'file',
content => $alert_config.to_yaml,
}
}
Note that I have switched from the deprecated hiera() function to its replacement, lookup().