This container image watches over the number of schedule-able nodes and cores of the cluster and resizes the number of replicas for the required resource. This functionality may be desirable for applications that need to be autoscaled with the size of the cluster, such as DNS and other services that scale with the number of nodes/pods in the cluster.
The Horizontal Pod Autoscaler is a top-level Kubernetes API resource. It is a closed feedback loop autoscaler which monitors CPU utilization of the pods and scales the number of replicas automatically. It requires the CPU resources to be defined for all containers in the target pods and also requires heapster to be running to provide CPU utilization metrics.
This horizontal cluster proportional autoscaler is a DIY container (because it is not a Kubernetes API resource) that provides a simple control loop that watches the cluster size and scales the target controller. The actual CPU or memory utilization of the target controller pods is not an input to the control loop, the sole inputs are number of schedulable cores and nodes in the cluster. There is no requirement to run heapster and/or provide CPU resource limits as in HPAs.
The ConfigMap provides the operator with the ability to tune the replica scaling explicitly.
Tell us about a new Kubernetes application
Never miss a thing! Sign up for our newsletter to stay updated.
Discover and learn about everything Kubernetes