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https://github.com/jthomperoo/horizontal-pod-autoscaler

Horizontal Pod Autoscaler, modified to work as a Custom Pod Autoscaler
https://github.com/jthomperoo/horizontal-pod-autoscaler

autoscaler custom-pod-autoscaler example hacktoberfest kubernetes-hpa

Last synced: 22 days ago
JSON representation

Horizontal Pod Autoscaler, modified to work as a Custom Pod Autoscaler

Host: GitHub
URL: https://github.com/jthomperoo/horizontal-pod-autoscaler
Owner: jthomperoo
License: apache-2.0
Archived: true
Created: 2019-11-19T18:42:50.000Z (about 5 years ago)
Default Branch: master
Last Pushed: 2022-12-18T14:23:56.000Z (almost 2 years ago)
Last Synced: 2024-08-05T17:23:35.165Z (4 months ago)
Topics: autoscaler, custom-pod-autoscaler, example, hacktoberfest, kubernetes-hpa
Language: Go
Homepage:
Size: 250 KB
Stars: 18
Watchers: 4
Forks: 3
Open Issues: 0
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE

Awesome Lists containing this project

awesome-cloud-native - horizontal-pod-autoscaler - Horizontal Pod Autoscaler, modified to work as a Custom Pod Autoscaler. (Autoscaler)

README

> # ARCHIVED AND READ ONLY - This project has been archived and marked as read only, it is no longer maintained.
> # You can still access the source code and run the examples, but no further code fixes will be made to this project.
> # Feel free to fork this if you want to continue working on it.

[![Build](https://github.com/jthomperoo/horizontal-pod-autoscaler/workflows/main/badge.svg)](https://github.com/jthomperoo/horizontal-pod-autoscaler/actions)
[![go.dev](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat)](https://pkg.go.dev/github.com/jthomperoo/horizontal-pod-autoscaler)
[![Go Report Card](https://goreportcard.com/badge/github.com/jthomperoo/horizontal-pod-autoscaler)](https://goreportcard.com/report/github.com/jthomperoo/horizontal-pod-autoscaler)
[![Documentation Status](https://readthedocs.org/projects/predictive-horizontal-pod-autoscaler/badge/?version=latest)](https://predictive-horizontal-pod-autoscaler.readthedocs.io/en/latest)
[![License](https://img.shields.io/:license-apache-blue.svg)](https://www.apache.org/licenses/LICENSE-2.0.html)

# Custom Pod Autoscaler - Horizontal Pod Autoscaler (CPA-HPA)

This is the Horizontal Pod Autoscaler (HPA), modified to work as a [Custom Pod Autoscaler
(CPA)](https://github.com/jthomperoo/custom-pod-autoscaler). This project is designed to be a starting point to allow
developers to quickly take a working Horizontal Pod Autoscaler and modify it as they need.

## What is a Custom Pod Autoscaler?

A Custom Pod Autoscaler is a way to write custom logic into Kubernetes scalers.
For more detailed overview, see the [Custom Pod Autoscaler
Framework](https://custom-pod-autoscaler.readthedocs.io/en/latest/).

## How do I use this project?

If you want to deploy this CPA-HPA onto your cluster, you first need to install the [Custom Pod Autoscaler
Operator](https://github.com/jthomperoo/custom-pod-autoscaler-operator), follow the [installation guide for
instructions for installing the
operator](https://github.com/jthomperoo/custom-pod-autoscaler-operator/blob/master/INSTALL.md).

## Overview of codebase

This project should be functionally similar/identical to the Kubernetes Horizontal Pod Autoscaler, with differences
being that this is run as a CPA rather than a Kubernetes controller. The code is largely copied from the Kubernetes
HPA and modified to work with the Custom Pod Autoscaler. Some restructuring of the architecture was required to fit
with how a CPA operates, with the HPA logic now split into two distinct parts; metric gathering and evaluation.

### Metric Gathering

The metric gathering stage takes in a resource to gather metrics for, and metric spec definitions for which metrics
to gather. Using this information the metrics are gathered and calculated, from metrics APIs. These metrics are then
serialised into JSON and output back to the CPA through stdout.

### Evaluation

The evaluation stage takes in the metrics gathered by the metric gathering stage and makes a decision - how many
replicas should the resource have. Once this decision has been made using data available the decision is serialised
into JSON and output back to the CPA through stdout to do the actual scaling.

### Configuration

There is some overlap in functionality between the the CPA and HPA, in this project precedence has been given to the
CPA functionality. For example, Kubernetes HPAs have the ability to set minimum and maximum replica counts, this
project removes those and instead relies on the CPA minimum and maximum replica counts. A Kubernetes HPA also contains
a ScaleTargetRef for deciding which resource to target when scaling; for this project only the ScaleTargetRef of the
CPA is used.

Deciding which metrics to use is done by using `MetricSpecs`, which are a key part of HPAs, and look like this:

```yaml
- type: Resource
resource:
name: cpu
target:
type: Utilization
averageUtilization: 50
```

To send these specs to the CPA-HPA, add a config option called `metrics` to the CPA, with a multiline string
containing the metric list. For example:

```yaml
config:
- name: metrics
value: |
- type: Resource
resource:
name: cpu
target:
type: Utilization
averageUtilization: 50
```

## Example

There is an example of how to use the Custom Pod Autoscaler - Horizontal Pod Autoscaler in [`/example`](./example).
The example has a simple deployment, taken from the [Kubernetes Horizontal Pod Autoscaler
walkthrough](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale-walkthrough/). The example also
contains the YAML definition of the CPA-HPA.

## More information

See the [wiki for more information, such as guides and
references](https://horizontal-pod-autoscaler.readthedocs.io/en/latest/).

## Developing this project
### Environment
Developing this project requires these dependencies:

* [Go](https://golang.org/doc/install) >= 1.17
* [staticcheck](https://staticcheck.io/docs/getting-started/) == `v0.3.0 (2022.1)`
* [Docker](https://docs.docker.com/install/)

To view the docs, you need Python 3 installed:

* [Python](https://www.python.org/downloads/) >= `3.8`

To view docs locally you need some Python dependencies, run:

```bash
pip install -r docs/requirements.txt
```

### Commands

* `make` - builds the CPA-HPA binary.
* `make docker` - builds the CPA-HPA image.
* `make lint` - lints the code.
* `make format` - formats the code.
* `make test` - runs the project tests.
* `make doc` - hosts the documentation locally, at `127.0.0.1:8000`.
* `make coverage` - shows the test coverage report.