Sometimes you find yourself in a situation where you need to enforce part of a catalog based on some condition. Perhaps you have custom facts that don't get set until the second Puppet run, or maybe you need to gate enforcement on something external that's not managed. Perhaps you just want to sanity check that a machine has been provisioned properly before being handed to Puppet, and you'd like a sane error message if not.

The assert type allows you to do dependency based partial catalogs. By adding an assert resource to your catalog, you can selectively skip any resources that express a dependency on it. This provides a straightforward way to manage partial enforcement without complex logic. It also retains a full catalog so you have a record of what was skipped and why.

The assert type includes simple fact assertions, several file path based assertions, and a command success assertion. See puppet describe assert for a full list of supported assertions.

Remember that Puppet handles undefined variables as undef which evaluates to false. This means that you can simply assert on a custom fact and it will fail if that fact does not exist.

You can invert an assert by setting its ensure parameter to absent.

assert { 'This should be applied':
  condition => true
} -> 
class { 'two': }

assert { 'This should NOT be applied':
  condition => false
} -> 
class { 'three': }

assert { 'This should be applied':
  ensure => absent,
  condition => false
} -> 
class { 'four': }

assert { 'This should be applied if the directory exists':
  directory => '/etc/custom'
} -> 
class { 'five': }

assert { 'This should be applied if the command succeeds':
  command => 'ping -c1 database.example.com'
} -> 
class { 'six': }

• Author: Ben Ford
• Email: [email protected]
• Twitter: @binford2k
• IRC (Freenode): binford2k

The initial development of this code was sponsored by Coverity.

Copyright (c) 2016 Ben Ford, [email protected]
Copyright (c) 2012 Puppet Labs, [email protected]
Copyright (c) 2012 Coverity.com, [email protected]

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