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tahu

This module is a collection of advanced functions for functionality in Puppet that is otherwise only available in Ruby. Checkout the list of features in the description

  1. Description
  2. Usage - Configuration options and additional functionality
  3. Development - Guide for contributing to the module
  4. Reference - Function Reference

(In case you wonder "Tahu" is the Polynesian Tuamoto "God of Knowledge and Magic", son of "Atea, the Creator").

Description

This module provides features for:

  • Eval of Puppet Language source text
  • Stacktrace information
  • Serialization and Deserialization
  • Type reflection
  • Data type parsing
  • Hiera 5 Puppet Language evaluation backend

Eval

The tahu::eval function allows you to evaluate Puppet Language source strings. Primarily intended to make it easier to use Deferred function evaluation as the Deferred data type does not support further processing of a value produced by deferred evaluation of a function and it also does not support lambdas.

For the security conscious, tahu::eval is no worse than EPP but it can return any value where EPP can only return a string. (In constrast ERB is much worse as it allows full access to the Ruby runtime).

Stacktrace

The functions tahu::where and tahu::stacktrace provides information how the logic ended up at a particular file and line. This is useful for custom error messages in functions, or for debugging purposes - answering "how did it end up calling this function?".

Type Reflection

Several functions allow getting more details about data types (an Integer data type for example has the attributes to and from) and there are functions to get such values. There are also functions to get detailed information how functions can be called, how objects and resource types can b created - what parameters they take and what their data types are.

This is useful in several cases - for example when reading information from a file that is then used in a call, or to create resources and you want to provide better error messages than just getting a crash when attempting to make the call/create the resource with the data that was given. Now you can check if the data is acceptable before making the call as this gives you an opportunity to provide a better error message.

Other use cases could be to filter out parameters given in data when they are not compatible with a particular version of a resource or object.

Serialization and Deserialization

Puppet can read/write RichData values with a Data compatible encoding. This is used by Puppet when a Catalog is sent from a master to an agent. Now you can do the same type of serializtion/deserialization. For example to read/write rich data from YAML files.

Data type parsing

The function tahu::to_type transforms a string into a data type. For example tahu::to_type("Integer[1,10]") would parse the string and return the actual type.

Usage

This modules contains advancd functions. Simply call them...

Limitations

This module requires Puppet 6.1.0 for several of the functions.

Development

Pull requests are accepted. Issues are tracked at github. This module was developed with PDK and documentation is generated with Puppet Strings.

Release Notes/Contributors/Etc. Optional

Written by Henrik Lindberg - Slack/IRC: helindbe.

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