Sunday, September 29, 2013

Puppet: create files from Array

Suppose I have such entry in a yaml file.
   - Cert1.cer
   - Cert2.cer

and I have all those *.cer files in mymodule/certs/ folder in Puppet.
I cannot do:
mycertificates = hiera('certificatefiles')

for mycertificate in $mycertificates :
    file {"/opt/oracle/certs/${mycertificate}":
       ensure => present,
       source => "puppet:///modules/mymodule/certs/${name}",

because if would be too intuitive and simple, and Puppet bans whatever is fluent and simple. Iterations are not supported, because Puppet believes Iterations are a bad concept (who need iterations by the way, when you can hardcode and copy/paste to death?).

This is the VERY ELEGANT Puppet approach (very intuitive, it took me days to figure it out):
define create_certificate_file($target_folder) {
  file { "${name}":
    ensure  => present,
    path    => "${target_folder}/${name}",
    source  => "puppet:///modules/mymodule/certs/${name}",

mycertificates = hiera('certificatefiles')

create_certificate_file {$mycertificates :
    target_folder => '/opt/oracle/certs/',

$mycertificates is an ARRAY, and Puppet has decided that whenever you invoke a define passing an array in the "name" field, it means implicitly that you want to repeat the define for each element of the array.
BE VERY CAREFUL not to write
invoke create_certificate_file {"${mycertificates}":
this would transform your array into a String "Cert1.cerCert2.cer" which defeats the purpose.

I hope this will save hours of frustration to the next poor beast falling victim to Puppet DSL.
PS incidentally, who needs Types? Life is good when you can implicitly convert an Array into a String, and waste hours troubleshooting the issue.... who need Objects and Classes? let's represent everything with a String and Hashmaps... let's be FLEXIBLE like molassa and spaghetti.

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