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Version: 2.4

Scale your cluster

Constellation provides all features of a Kubernetes cluster including scaling and autoscaling.

Worker node scaling​

Autoscaling​

Constellation comes with autoscaling disabled by default. To enable autoscaling, find the scaling group of worker nodes:

worker_group=$(kubectl get scalinggroups -o json | jq -r '.items[].metadata.name | select(contains("worker"))')
echo "The name of your worker scaling group is '$worker_group'"

Then, patch the autoscaling field of the scaling group resource to true:

kubectl patch scalinggroups $worker_group --patch '{"spec":{"autoscaling": true}}' --type='merge'
kubectl get scalinggroup $worker_group -o jsonpath='{.spec}' | jq

The cluster autoscaler now automatically provisions additional worker nodes so that all pods have a place to run. You can configure the minimum and maximum number of worker nodes in the scaling group by patching the min or max fields of the scaling group resource:

kubectl patch scalinggroups $worker_group --patch '{"spec":{"max": 5}}' --type='merge'
kubectl get scalinggroup $worker_group -o jsonpath='{.spec}' | jq

The cluster autoscaler will now never provision more than 5 worker nodes.

If you want to see the autoscaling in action, try to add a deployment with a lot of replicas, like the following Nginx deployment. The number of replicas needed to trigger the autoscaling depends on the size of and count of your worker nodes. Wait for the rollout of the deployment to finish and compare the number of worker nodes before and after the deployment:

kubectl create deployment nginx --image=nginx --replicas 150
kubectl -n kube-system get nodes
kubectl rollout status deployment nginx
kubectl -n kube-system get nodes

Manual scaling​

Alternatively, you can manually scale your cluster up or down:

  1. Find your Constellation resource group.
  2. Select the scale-set-workers.
  3. Go to settings and scaling.
  4. Set the new instance count and save.

Control-plane node scaling​

Control-plane nodes can only be scaled manually and only scaled up!

To increase the number of control-plane nodes, follow these steps:

  1. Find your Constellation resource group.
  2. Select the scale-set-controlplanes.
  3. Go to settings and scaling.
  4. Set the new (increased) instance count and save.

If you scale down the number of control-planes nodes, the removed nodes won't be able to exit the etcd cluster correctly. This will endanger the quorum that's required to run a stable Kubernetes control plane.