Jira (PUP-9714) Add support for nested hiera interpolation

[Nick Bertrand (JIRA)]

Nick Bertrand created an issue

Puppet / PUP-9714 Add support for nested hiera interpolation Issue Type: New Feature Assignee: Unassigned Created: 2019/05/21 3:26 PM Priority: Normal Reporter: Nick Bertrand This commit adds support for two levels of nested hiera interpolations. For example, given a fact called hostgroup with value group1, the following hiera data would have local_users::add::users.root.password set to $6$.... --- group1_root_password: $6$.... local_users::add::users: root: password: '%{lookup("%{facts.hostgroup}_root_password")}' If this is useful for merging, I would be glad to update any necessary documentation. Add Comment

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[Josh Cooper (JIRA)]

Josh Cooper updated an issue

Puppet / PUP-9714 Add support for nested hiera interpolation

Change By: Josh Cooper Sub-team: Language

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[Josh Cooper (JIRA)]

Josh Cooper updated an issue

Puppet / PUP-9714 Add support for nested hiera interpolation

Change By: Josh Cooper Team: Server

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[Henrik Lindberg (JIRA)]

Henrik Lindberg commented on PUP-9714

Re: Add support for nested hiera interpolation Here is an example of how the same can be achieved with hiera 5 and a simple backend function written in Puppet Language. # Do whatever is needed for a special key here that interpolates a value to form another key that is looked up. # This example is hardcoded for one key only, but could easily read data from a file, support multiple keys etc. # function mymodule::special_key(Variant[String, Numeric] $key, Hash $options, Puppet::LookupContext $context) { unless $key == 'hostgroup_specific_root_password' { $context.not_found() # will return from this function } lookup("${facts[hostgroup]}_root_password") } Then add that function to hiera.yaml as a lookup_key kind of function, and use hiera regular interpolation in the data to get that key into the value of a hash. Using the example in the description this is what is in the data where the special value is wanted:

--- group1_root_password: $6$.... local_users::add::users: root:

password: '%{alias("hostgroup_specific_root_password")}' Documentation for lookup_key kind of backend functions is here: https://puppet.com/docs/puppet/4.9/hiera_custom_lookup_key.html#calling-conventions-for-lookupkey-functions

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[Henrik Lindberg (JIRA)]

Henrik Lindberg commented on PUP-9714

Re: Add support for nested hiera interpolation

The above could be turned into a "key mapper" function. A user of the function would specify "path" to a data file, and the data file would contain the key mapping: --- hostgroup_specific_root_password: %{facts.hostgroup}_root_password' The function would read the data file given to the function in options[path], using a read_yaml function. It can then cache this result using the $context cache methods. On a lookup, it gets the data from the cache, if the key being looked up is present (e.g. 'hostgroup_specific_root_password'), it gets the value and calls $context.interpolate to interpolate it. This forms the new key, which it then uses in a call to lookup - the returned value from lookup is returned from the function. This generalized version would only be a couple of lines longer than the first example.

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[Henrik Lindberg (JIRA)]

Henrik Lindberg commented on PUP-9714

Re: Add support for nested hiera interpolation

I would much rather see that the requested feature is solved via use of a lookup_key kind of function than modifying hiera's interpolation to do nested interpolation.

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[Robert August Vincent II (JIRA)]

Robert August Vincent II commented on PUP-9714

Re: Add support for nested hiera interpolation

There needs to be a docs change, as well.

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[Maggie Dreyer (Jira)]

Maggie Dreyer commented on PUP-9714

Re: Add support for nested hiera interpolation

In general, we are not prioritizing any Hiera features for the time being. If that changes, we can revisit this.

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