Why is Puppet considered idempotent?

Puppet is considered idempotent because it can safely apply the same configuration multiple times without changing the state of the system beyond the initial application. This means that when you run Puppet on a system that is already in the desired state defined by the Puppet manifest, it will recognize that the system does not require any changes and thus will leave it as is.

This property ensures that running Puppet again does not lead to unintended modifications, making it safe and predictable. Even if you trigger Puppet runs frequently, as long as the infrastructure is already in compliance with the specified state, no further actions will be taken by Puppet. This feature is pivotal in maintaining stability and consistency in configurations across systems, especially in large deployments.

The other options do not accurately represent the idempotency principle. For instance, requiring a configuration change or applying changes each run contradicts the concept of idempotence, as it implies that multiple runs could lead to different states. Additionally, while Puppet may utilize REST APIs, this alone does not imply or contribute to its idempotent nature.