Cluster Autoscaler on CloudStack
The cluster autoscaler on CloudStack scales worker nodes within any specified cluster. It runs as a Deployment
in your cluster.
This README will go over some of the necessary steps required to get the cluster autoscaler up and running.
Requirements
Cluster Autoscaler requires Apache CloudStack 4.16 onward as well as Kubernetes v1.16.0 or greater.
Deployment
The CloudStack kubernetes cluster can be autoscaled via the scaleKubernetesCluster
by passing autoscalingenabled=true
along with
the minsize
and maxsize
parameters API from 4.16 onwards. eg:
scaleKubernetesCluster id=<cluster-id> autoscalingenabled=true minsize=<minsize> maxsize=<maxsize>
Autoscaling on the cluster can be disabled by passing autoscalingenabled=false
. This will delete the deployment and leave the cluster
at its current size. eg:
scaleKubernetesCluster id=<cluster-id> autoscalingenabled=false
To manually deploy the cluster autoscaler, please follow the guide below :
To configure API access to your CloudStack management server, you need to create a secret containing a cloud-config
that is suitable for your environment.
cloud-config
should look like this:
[Global]
api-url = <CloudStack API URL>
api-key = <CloudStack API Key>
secret-key = <CloudStack API Secret>
The access token needs to be able to execute the listKubernetesClusters
and scaleKubernetesCluster
APIs.
To create the secret, use the following command:
kubectl -n kube-system create secret generic cloudstack-secret --from-file=cloud-config
Finally, to deploy the autoscaler, modify the cluster-autoscaler-standard.yaml
with the cluster id, minsize and maxsize located
here and execute it
kubectl apply -f cluster-autoscaler-standard.yaml
Common Notes and Gotchas:
- The automated deployment of the autoscaler will run with the defaults configured here. To change it, alter the file and deploy it again.
- By default, cluster autoscaler will not terminate nodes running pods in the kube-system namespace. You can override this default behaviour by passing in the
--skip-nodes-with-system-pods=false
flag.
- By default, cluster autoscaler will wait 10 minutes between scale down operations, you can adjust this using the
--scale-down-delay
flag. E.g. --scale-down-delay=5m
to decrease the scale down delay to 5 minutes.