kubernetes-sigs/controller-runtime
Controller Runtime
This project provides a framework for building Kubernetes operators and custom controllers. It offers a set of libraries designed to manage the lifecycle of cluster resources, enabling developers to synchronize the actual state of a cluster with a desired configuration through event-driven reconciliation loops.
The framework distinguishes itself by providing a manager-orchestrated environment that coordinates multiple controllers and webhooks within a single process. It includes built-in support for optimistic concurrency control to prevent update conflicts and utilizes in-memory informer caching to maintain a synchronized local view of cluster state, which reduces load on the API server.
Beyond core reconciliation, the project includes tools for schema-based resource mapping, allowing for the registration of custom resource definitions. It also provides mechanisms for admission control, enabling the validation and mutation of resource requests to enforce compliance before data is persisted. The framework includes a dedicated testing suite that spins up ephemeral, isolated API server environments to validate controller logic against real cluster behavior.
