Gatekeeper

Gatekeeper manages enforcing policies and governance in Kubernetes environments, a task that is otherwise manual, error-prone, and time-consuming. It leverages the Open Policy Agent (OPA) to execute policies defined in the Rego language, providing a powerful, flexible, and portable policy engine.

Technically, Gatekeeper operates as a validating and mutating webhook within the Kubernetes ecosystem. It integrates with Kubernetes through Custom Resource Definitions (CRDs) for instantiating and extending policy libraries. This includes ConstraintTemplates and Constraints for validation, and similar CRDs for mutation support. When resources are created, updated, or deleted, Gatekeeper intercepts these operations via admission controller webhooks, ensuring compliance with predefined policies. Additionally, its audit functionality allows administrators to identify resources that violate policies, even after they have been deployed.

Operationally, Gatekeeper is highly customizable and extensible. It supports external data sources and provides a community-owned policy library that includes a wide range of validation and mutation policies. Administrators can use tools like kustomize to install and manage these policies efficiently. However, managing a large number of policies and constraints can become complex, and the performance of Gatekeeper may degrade if not properly optimized, especially in large-scale Kubernetes clusters.

From a technical details perspective, Gatekeeper relies on Rego for policy definition, which allows for complex logic and conditional checks. The use of CRDs ensures native Kubernetes integration, making policy enforcement seamless within the Kubernetes lifecycle. However, this also means that the effectiveness of Gatekeeper is closely tied to the performance and stability of the underlying Kubernetes infrastructure.