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

Supplying the $backends variable to a Puppet template by defining it in a class is a standard practice in Puppet. When you define a variable within a class, you can ensure that it is scoped appropriately and that it can be accessed by templates associated with that class. This keeps your Puppet manifests organized and manageable, as variables defined in a class are typically used for specific resources or configurations related to that class.

Defining the variable in a class also allows Puppet's resource declaration and variable scoping rules to govern how the variable is accessed later on, ensuring that the value is available when the template is rendered. This approach aligns with Puppet’s design principles of modularity and reusability, making it easier to maintain and understand the configurations being applied.

Although other methods such as global variables, external JSON files, and Puppet facts can potentially be used to pass data to templates, defining the variable in a class is more in line with best practices for organizing code and maintaining clarity within your Puppet configurations.