Kubecontroller manager is a process that monitors satate of the various components and works to bring the system to work in the desired state
The node-controller monitors the status of the nodes and takes neccesary actions to keep the application running through kubeapi server. By default it checks the status every 5 seconds. If a node is not sending the heartbeat for 40 sec, its is marked unreachable. The node controller waits for 5 minutes for node to come back up. If the node doesn't come back, it removes the pods assigned to the node and provisions them on to the healthy one if the pods are part of replica sets.
kube-controller-manager.service can be used to change the default settings S