Kubernetes Autoscaler

  • By Canonical Kubernetes
Channel Revision Published Runs on
latest/stable 36 17 Apr 2024
Ubuntu 22.04 Ubuntu 20.04
latest/candidate 36 15 Apr 2024
Ubuntu 22.04 Ubuntu 20.04
latest/beta 34 17 Apr 2024
Ubuntu 22.04 Ubuntu 20.04
latest/edge 34 09 Aug 2023
Ubuntu 22.04 Ubuntu 20.04
1.30/beta 34 19 Apr 2024
Ubuntu 22.04 Ubuntu 20.04
1.30/edge 34 13 Mar 2024
Ubuntu 22.04 Ubuntu 20.04
1.29/stable 36 17 Apr 2024
Ubuntu 22.04 Ubuntu 20.04
1.29/candidate 36 15 Apr 2024
Ubuntu 22.04 Ubuntu 20.04
1.29/beta 34 17 Apr 2024
Ubuntu 22.04 Ubuntu 20.04
1.29/edge 34 21 Aug 2023
Ubuntu 22.04 Ubuntu 20.04
1.28/stable 33 22 Aug 2023
Ubuntu 22.04 Ubuntu 20.04
1.28/beta 33 07 Aug 2023
Ubuntu 22.04 Ubuntu 20.04
1.28/edge 34 09 Aug 2023
Ubuntu 22.04 Ubuntu 20.04
1.27/stable 31 12 Jun 2023
Ubuntu 22.04 Ubuntu 20.04
1.27/candidate 29 10 Apr 2023
Ubuntu 22.04 Ubuntu 20.04
1.27/beta 29 10 Apr 2023
Ubuntu 22.04 Ubuntu 20.04
1.27/edge 26 11 Mar 2023
Ubuntu 22.04 Ubuntu 20.04
1.26/stable 25 27 Feb 2023
Ubuntu 22.04 Ubuntu 20.04
1.26/candidate 25 27 Feb 2023
Ubuntu 22.04 Ubuntu 20.04
1.26/beta 27 08 Apr 2023
Ubuntu 22.04 Ubuntu 20.04
juju deploy kubernetes-autoscaler
Show information

Platform:

kubernetes-autoscaler

Description

This charm scales an existing juju deployed kubernetes cluster using the kubernetes cluster autoscaler with a juju cloud provider.

Installation

Installing the charm from charmhub into a kubernetes cluster

# create a namespace for the autoscaler
juju add-model kubernetes-cluster-autoscaler
# deploy the application into the cluster
juju deploy kubernetes-autoscaler --trust 

Usage/Configuration

Provide this charm application with credentials to add/remove units from an existing juju deployed kubernetes, and the cluster will resize the number of worker nodes based on the needs of scale. Node groups are defined by the application name in the deployed model. The autoscaler will not create a cluster, but will grow and shrink as demand requires

Setting controller config

You can retrieve the necessary configuration information with the following commands.


NOTE: The kubernetes-controller is the juju controller which holds the charmed-kubernetes model, not the model which holds the kubernetes-autoscaler.


KUBE_CONTROLLER=<kubernetes-controller>
API_ENDPOINTS=$(
    juju show-controller $KUBE_CONTROLLER --format json |
    jq -rc '.[].details["api-endpoints"] |
    join(",")'
)
CA_CERT=$(
    juju show-controller $KUBE_CONTROLLER --format json |
    jq -rc '.[].details["ca-cert"]' |
    base64 -w0
)
USER=$(
    juju show-controller $KUBE_CONTROLLER --format json |
    jq -rc '.[].account.user'
)
PASSWORD=$(
    juju show-controller $KUBE_CONTROLLER --show-password --format json |
    jq -rc '.[].account.password'
)

The autoscaler is recommended to run on a control-plane node so that it isn’t reaped when a worker node is scaled down. Ensure the control-plane nodes do not have the taint juju.is/kubernetes-control-plane=true:NoSchedule applied so that they can run pods.

kubectl get nodes -o custom-columns=NAME:.metadata.name,TAINTS:.spec.taints --no-headers 

In order to remove the taint, for each control-plane node run:

kubectl taint node $NODE juju.is/kubernetes-control-plane=true:NoSchedule- 

Deploy the charm into a k8s type juju model (not a machine model)

juju deploy kubernetes-autoscaler --constraints "tags=node.juju-application=kubernetes-control-plane"

Provide these as configuration to the deployed application

juju config kubernetes-autoscaler \
    juju_api_endpoints="${API_ENDPOINTS}" \
    juju_ca_cert="${CA_CERT}"\
    juju_username="${USER}"\
    juju_password="${PASSWORD}"

After this, you’ll need to find the model which contains the application to scale

juju models -c $KUBE_CONTROLLER --format json | jq -cr '.models[]|{name,"model-uuid"}'

Using the correct model-uuid, set the default_model_uuid.

juju config kubernetes-autoscaler juju_default_model_uuid=$MODEL_UUID

Lastly, pick the worker application to scale. Usually this is kubernetes-worker.

juju config kubernetes-autoscaler juju_scale="- {min: 3, max: 5, application: kubernetes-worker}"

See below for more complicated examples.

juju_default_model_uuid: "cdcaed9f-336d-47d3-83ba-d9ea9047b18c"   # within this juju model
juju_scale: '- {min: 3, max: 5, application: kubernetes-worker}'  # indicates 3 to 5 kubernetes-worker nodes
# indicates 0 to 10 nodes of GPU based workers
juju_scale: '- {min: 1, max: 10, application: kubernetes-worker-gpu}'
# indicates 0 to 10 nodes of GPU based workers and 3 to 5 kubernetes-worker nodes
juju_scale: |-
   - {min: 1, max: 10, application: kubernetes-worker-gpu}
   - {min: 3, max: 5, application: kubernetes-worker}

Be sure that the yaml presented in juju_scale is valid json or yaml.


Help improve this document in the forum (guidelines). Last updated 11 months ago.