OPA Gatekeeper
OPA Gatekeeper is an open-source policy controller for Kubernetes that enforces custom resource definitions (CRDs) to implement policies and constraints on cluster resources. It leverages the Open Policy Agent (OPA) engine to evaluate policies written in Rego, a declarative query language, ensuring compliance with security, governance, and operational standards. By integrating with Kubernetes admission control, it validates and mutates resource requests before they are persisted in the cluster.
Developers should learn OPA Gatekeeper when working in Kubernetes environments to enforce security policies, such as preventing privileged containers or ensuring resource limits, and governance rules, like labeling or annotation requirements. It is particularly useful in multi-tenant clusters, CI/CD pipelines, and regulated industries to automate compliance and reduce manual oversight, helping prevent misconfigurations that could lead to vulnerabilities or operational issues.