Operator Pattern

operator pattern?: A specialized controller used to manage a custom resource. It lets you extend the cluster's behavior w/o modifying k8s code by linking controllers to one or more custom resources.

• publishing a Service to applications that don't support Kubernetes APIs to discover them

How it works?

1. Custom Resource is running.

2. Controller queries the control plane to find out what Custom Resource is configured.

3. An Operator tells the API server, how to align the current state with the desired state.

Terms

1. Control loop
2. Custom resource
3. Control plane: Formerly called Master Node