Triggering autoscaling

Lets test the CPA that we installed in the previous section. Currently we're running a 3 node cluster:

~$kubectl get nodes

NAME                                            STATUS   ROLES    AGE   VERSION

ip-10-42-109-155.us-east-2.compute.internal     Ready    <none>   76m   v1.31-eks-036c24b

ip-10-42-142-113.us-east-2.compute.internal     Ready    <none>   76m   v1.31-eks-036c24b

ip-10-42-80-39.us-east-2.compute.internal       Ready    <none>   76m   v1.31-eks-036c24b

Based on autoscaling parameters defined in the ConfigMap, we see cluster proportional autoscaler scale CoreDNS to 2 replicas:

~$kubectl get po -n kube-system -l k8s-app=kube-dns

NAME                       READY   STATUS    RESTARTS   AGE

coredns-5db97b446d-5zwws   1/1     Running   0          66s

coredns-5db97b446d-n5mp4   1/1     Running   0          89m

If we increased the size of the EKS cluster to 5 nodes, Cluster Proportional Autoscaler will scale up the number of replicas of CoreDNS to accommodate for it:

~$aws eks update-nodegroup-config --cluster-name $EKS_CLUSTER_NAME \

--nodegroup-name $EKS_DEFAULT_MNG_NAME --scaling-config desiredSize=$(($EKS_DEFAULT_MNG_DESIRED+2))

~$aws eks wait nodegroup-active --cluster-name $EKS_CLUSTER_NAME \

--nodegroup-name $EKS_DEFAULT_MNG_NAME

~$kubectl wait --for=condition=Ready nodes --all --timeout=120s

Kubernetes now shows the 5 nodes in a Ready state:

~$kubectl get nodes

NAME                                          STATUS   ROLES    AGE   VERSION

ip-10-42-10-248.us-west-2.compute.internal    Ready    <none>   61s   v1.31-eks-036c24b

ip-10-42-10-29.us-west-2.compute.internal     Ready    <none>   124m  v1.31-eks-036c24b

ip-10-42-11-109.us-west-2.compute.internal    Ready    <none>   6m39s v1.31-eks-036c24b

ip-10-42-11-152.us-west-2.compute.internal    Ready    <none>   61s   v1.31-eks-036c24b

ip-10-42-12-139.us-west-2.compute.internal    Ready    <none>   6m20s v1.31-eks-036c24b

And we can see that the number of CoreDNS Pods has increased:

~$kubectl get po -n kube-system -l k8s-app=kube-dns

NAME                       READY   STATUS    RESTARTS   AGE

coredns-657694c6f4-klj6w   1/1     Running   0          14h

coredns-657694c6f4-tdzsd   1/1     Running   0          54s

coredns-657694c6f4-wmnnc   1/1     Running   0          14h

You can take a look at the CPA logs to see how it responded to the change in the number of nodes in our cluster:

~$kubectl logs deployment/cluster-proportional-autoscaler -n kube-system

{"includeUnschedulableNodes":true,"max":6,"min":2,"nodesPerReplica":2,"preventSinglePointFailure":true}

I0801 15:02:45.330307       1 k8sclient.go:272] Cluster status: SchedulableNodes[1], SchedulableCores[2]

I0801 15:02:45.330328       1 k8sclient.go:273] Replicas are not as expected : updating replicas from 2 to 3