Controller [glossary]deterministic
A control loop that watches the shared state of the cluster through the apiserver and makes changes attempting to move the current state towards the desired state.
In Kubernetes, controllers are control loops that watch the state of your [cluster](#gloss:cluster), then make or request changes where needed. Each controller tries to move the current cluster state closer to the desired state.
Controllers watch the shared state of your cluster through the [apiserver](#gloss:kube-apiserver) (part of the [control-plane](#gloss:control-plane)).
Some controllers also run inside the control plane, providing control loops that are core to Kubernetes' operations. For example: the deployment controller, the daemonset controller, the namespace controller, and the persistent volume controller (and others) all run within the [kube-controller-manager](#gloss:kube-controller-manager).