Which method can be used to supply the $backends variable to a Puppet template?

The method of defining the $backends variable in a class is effective because it leverages Puppet's strong class-based structure to manage and encapsulate data. When a variable is defined within a class, it can be accessed by templates that are declared within the same scope or from the class itself. This promotes better organization and the principles of encapsulation, making it easier to maintain and reuse code across different manifests and modules.

When a variable is part of a class, it is also easier to apply conditions or logic related to that variable, allowing for dynamic configuration of resources or templates based on the state defined within the class. This approach seamlessly integrates the variable into the Puppet run, allowing templates to use it without the need for workarounds or external dependencies.

In contrast, global variables can lead to a less structured approach because they can be accessed from anywhere in your Puppet code, which may introduce complications in larger systems. Using external JSON files or Puppet facts for passing data is viable but often involves additional steps such as parsing or processing the data, which can introduce more complexity compared to simply defining a variable within a class.