use an onlyif+test check

If the human-readable text file is newer than the database file, (re)create

This solves the issue outlined in https://github.com/thias/puppet-postfix/issues/113 & https://github.com/thias/puppet-postfix/pull/114 but in a different way; the creates attribute is not useful here.

https://docs.puppet.com/puppet/latest/type.html#exec-attribute-creates

A file to look for before running the command. The command will only run if the file doesn’t exist.

If the file does exist, but the originating resource is updated, the .db file is not recreated.

Here's a quick example:

# cat creates.pp
node default {

  file { "/tmp/file1":
    ensure  => present,
    content => "test\n",
  }

  exec { "/tmp/file2":
    command     => "/bin/cat /tmp/file1 > /tmp/file2",
    subscribe   => File["/tmp/file1"],
    creates     => "/tmp/file2",
  }

}

#puppet apply creates.pp
Notice: Compiled catalog for SERVER in environment production in 0.38 seconds
Notice: /Stage[main]/Main/Node[default]/File[/tmp/file1]/ensure: created
Notice: /Stage[main]/Main/Node[default]/Exec[/tmp/file2]/returns: executed successfully
Notice: /Stage[main]/Main/Node[default]/Exec[/tmp/file2]: Triggered 'refresh' from 1 events
Notice: Finished catalog run in 0.17 seconds
# cat /tmp/file1
test
cat /tmp/file2
test

Now, change file1:

# cat creates.pp
node default {

  file { "/tmp/file1":
    ensure  => present,
    content => "quux\n",
  }

  exec { "/tmp/file2":
    command     => "/bin/cat /tmp/file1 > /tmp/file2",
    subscribe   => File["/tmp/file1"],
    creates     => "/tmp/file2",
  }

}

# puppet apply creates.pp
Notice: Compiled catalog for SERVER in environment production in 0.38 seconds
Notice: /Stage[main]/Main/Node[default]/File[/tmp/file1]/content: content changed '{md5}d8e8fca2dc0f896fd7cb4cb0031ba249' to '{md5}d3b07a382ec010c01889250fce66fb13'
Notice: /Stage[main]/Main/Node[default]/Exec[/tmp/file2]: Triggered 'refresh' from 1 events
Notice: Finished catalog run in 0.12 seconds
# cat /tmp/file1
quux
# cat /tmp/file2
test

The puppet output isn't helpful here - file2 is "triggered" but because the file already exists it actually doesn't update.

The fix:

cat creates.pp
node default {

  file { "/tmp/file1":
    ensure  => present,
    content => "quux\n",
  }

  exec { "/tmp/file2":
    command     => "/bin/cat /tmp/file1 > /tmp/file2",
    subscribe   => File["/tmp/file1"],
    onlyif      => "/usr/bin/test /tmp/file1 -nt /tmp/file2",
  }

}

puppet apply creates.pp
Notice: Compiled catalog for SERVER in environment production in 0.36 seconds
Notice: /Stage[main]/Main/Node[default]/Exec[/tmp/file2]/returns: executed successfully
Notice: Finished catalog run in 0.23 seconds
# cat /tmp/file1
quux
# cat /tmp/file2
quux

thias / puppet-postfix

use an onlyif+test check #118