horizontalpodautoscalerx

Kubernetes controller that extends the Kubernetes HorizontalPodAutoscaler (HPA) with dynamic overrides, and fallbacks if it detects scaling failure.

Note: This has not been tested in a production environment, open an issue and tag me if you want to use it in production.

Description

Create a HorizontalPodAutoscalerX resource, e.g.

apiVersion: autoscalingx.rrethy.io/v1
kind: HorizontalPodAutoscalerX
metadata:
  name: horizontalpodautoscalerx-sample
spec:
  hpaTargetName: myhpa
  fallback:
    minReplicas: 50
    duration: "120s" # the duration hpa scaling should fail before fallback kicks in
  minReplicas: 10

Then have an HPA that targets a deployment, e.g.

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: myhpa
spec:
  maxReplicas: 100
  metrics: [] # fill in with your metrics

You MUST NOT specify minReplicas in the HPA, as this controller will override it.

To define an override, either dynamically or in GitOps, create a HPAOverride CR, e.g.

apiVersion: autoscalingx.rrethy.io/v1
kind: HPAOverride
metadata:
  name: hpaoverride-sample
spec:
  hpaTargetName: myhpa
  minReplicas: 100
  duration: "3600s"
  time: "2015-01-01T00:00:00Z" # the start time for the override

Installation

A prebuilt package is available at https://github.com/RRethy/horizontalpodautoscalerx/pkgs/container/horizontalpodautoscalerx.

Getting Started

Prerequisites

• go version v1.23.0+
• docker version 17.03+.
• kubectl version v1.11.3+.
• Access to a Kubernetes v1.11.3+ cluster.

To Deploy on the cluster

Build and push your image to the location specified by IMG:

make docker-build docker-push IMG=<some-registry>/horizontalpodautoscalerx:tag

NOTE: This image ought to be published in the personal registry you specified. And it is required to have access to pull the image from the working environment. Make sure you have the proper permission to the registry if the above commands don’t work.

Install the CRDs into the cluster:

make install

Deploy the Manager to the cluster with the image specified by IMG:

make deploy IMG=<some-registry>/horizontalpodautoscalerx:tag

NOTE: If you encounter RBAC errors, you may need to grant yourself cluster-admin privileges or be logged in as admin.

Create instances of your solution You can apply the samples (examples) from the config/sample:

kubectl apply -k config/samples/

NOTE: Ensure that the samples has default values to test it out.

To Uninstall

Delete the instances (CRs) from the cluster:

kubectl delete -k config/samples/

Delete the APIs(CRDs) from the cluster:

make uninstall

UnDeploy the controller from the cluster:

make undeploy

Contributing

Open an issue and tag me (@RRethy) before considering contributing to this project.

License

Copyright 2025.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.