Escalator

Escalator is a batch or job optimized horizontal autoscaler for Kubernetes

It is designed for large batch or job based workloads that cannot be force-drained and moved when the cluster needs to scale down - Escalator will ensure pods have been completed on nodes before terminating them. It is also optimised for scaling up the cluster as fast as possible to ensure pods are not left in a pending state.

Key Features

Calculate requests and capacity to determine whether to scale up, down or to stay at the current scale
Waits until non-daemonset pods on nodes have completed before terminating the node
Designed to work on selected auto-scaling groups to allow the default Kubernetes Autoscaler to continue to scale service based workloads
Automatically terminate oldest nodes first
Support for slack space to ensure extra space in the event of a spike of scheduled pods
Does not terminate or factor cordoned nodes into calculations - allows cordoned nodes to persist for debugging
Support for different cloud providers - AWS only at the moment
Scaling and utilisation metrics
Leader election so you can run a HA Deployment inside a cluster.
Basic support for multiple different types of instances in a Node Group.

The need for this autoscaler is derived from our own experiences with very large batch workloads being scheduled and the default autoscaler not scaling up the cluster fast enough. These workloads can't be force-drained by the default autoscaler and must complete before the node can be terminated.

Documentation and Design

See Docs

Requirements

Kubernetes version 1.24+. Escalator has been tested and deployed on 1.24+ and newer. Older versions of Kubernetes may have bugs or issues that will prevent it from functioning properly.
Go version 1.20+
Dependencies and their locked versions can be found in go.mod and go.sum.

Building

# Fetch dependencies and build Escalator
make build

How to run - Quick Start

Locally (out of cluster)

go run cmd/main.go --kubeconfig=~/.kube/config --nodegroups=nodegroups_config.yaml

Deployment (in cluster)

See Deployment for full Deployment documentation.

# Build the docker image
docker build -t atlassian/escalator .

# Create RBAC configuration
kubectl create -f docs/deployment/escalator-rbac.yaml

# Create config map - modify to suit your needs
kubectl create -f docs/deployment/escalator-cm.yaml

# Create deployment
kubectl create -f docs/deployment/escalator-deployment.yaml

Configuring

See Configuration

Testing

make test

Test a specific package

For example, to test the controller package:

go test ./pkg/controller

Contributors

Pull requests, issues and comments welcome. For pull requests:

Add tests for new features and bug fixes
Follow the existing style (we are using goreturns to format and lint escalator)
Separate unrelated changes into multiple pull requests

See the existing issues for things to start contributing.

For bigger changes, make sure you start a discussion first by creating an issue and explaining the intended change.

Atlassian requires contributors to sign a Contributor License Agreement, known as a CLA. This serves as a record stating that the contributor is entitled to contribute the code/documentation/translation to the project and is willing to have it used in distributions and derivative works (or is willing to transfer ownership).

Prior to accepting your contributions we ask that you please follow the appropriate link below to digitally sign the CLA. The Corporate CLA is for those who are contributing as a member of an organization and the individual CLA is for those contributing as an individual.