From a766d28b300b1b89664b7d89d59b4404ee7b7d67 Mon Sep 17 00:00:00 2001 From: Tim Bannister Date: Mon, 12 Oct 2020 18:36:23 +0100 Subject: [PATCH] Provide example of direct control for Controller concept --- content/en/docs/concepts/architecture/controller.md | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/content/en/docs/concepts/architecture/controller.md b/content/en/docs/concepts/architecture/controller.md index 2705cdfcb7..8f70bdc05c 100644 --- a/content/en/docs/concepts/architecture/controller.md +++ b/content/en/docs/concepts/architecture/controller.md @@ -96,6 +96,16 @@ the current state closer in line. nodes in your cluster. See [Cluster autoscaling](/docs/tasks/administer-cluster/cluster-management/#cluster-autoscaling)). +The important point here is that the controller makes some change to bring about +your desired state, and then reports current state back to your cluster's API server. +Other control loops can observe that reported data and take their own actions. + +In the thermostat example, if the room is very cold then a different controller +might also turn on a frost protection heater. With Kubernetes clusters, the control +plane indirectly works with IP address management tools, storage services, +cloud provider APIS, and other services by +[extending Kubernetes](/docs/concepts/extend-kubernetes/) to implement that. + ## Desired versus current state {#desired-vs-current} Kubernetes takes a cloud-native view of systems, and is able to handle