[openstack-dev] [TripleO] Alternative to empty string for default values in Heat

Ben Nemec openstack at nemebean.com
Fri Mar 23 17:46:43 UTC 2018

On 03/23/2018 11:54 AM, Giulio Fidente wrote:
> On 03/23/2018 05:43 PM, Wojciech Dec wrote:
>> Hi All,
>> I'm converting a few heat service templates that have been working ok
>> with puppet3 modules to run with Puppet 4, and am wondering if there is
>> a way to pass an "undefined" default via heat to allow "default" values
>> (eg params.pp) of the puppet modules to be used?
>> The previous (puppet 3 working) way of passing an empty string in heat
>> doesn't work, since Puppet 4 interprets this now as the actual setting.
> yaml allows use of ~ to represent null
> it looks like in a hiera lookup that is resolved as the "nil" value, not
> sure if that is enough to make the default values for a class to apply

Interesting.  That would be simpler than what we've been doing, which is 
to use a Heat conditional to determine whether a particular piece of 
hieradata is populated.  At least that's the method I'm aware of.  The 
workers settings are an example of this: 

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