Scale cluster

How to scale your cluster.

When you are scaling your EKS Anywhere cluster, consider the number of nodes you need for your control plane and for your data plane. Each plane can be scaled horizontally (add more nodes) or vertically (provide nodes with more resources). In each case you can scale the cluster manually, semi-automatically, or automatically.

See the Kubernetes Components documentation to learn the differences between the control plane and the data plane (worker nodes).

Manual cluster scaling

Horizontally scaling the cluster is done by increasing the number for the control plane or worker node groups under the Cluster specification.

NOTE: If etcd is running on your control plane (the default configuration) you should scale your control plane in odd numbers (3, 5, 7…).

apiVersion: anywhere.eks.amazonaws.com/v1
kind: Cluster
metadata:
  name: test-cluster
spec:
  controlPlaneConfiguration:
    count: 1     # increase this number to horizontally scale your control plane
...    
  workerNodeGroupsConfiguration:
  - count: 1     # increase this number to horizontally scale your data plane

Vertically scaling your cluster is done by updating the machine config spec for your infrastructure provider. For a vSphere cluster an example is

NOTE: Not all providers can be vertically scaled (e.g. bare metal)

apiVersion: anywhere.eks.amazonaws.com/v1
kind: VSphereMachineConfig
metadata:
  name: test-machine
  namespace: default
spec:
  diskGiB: 25       # increase this number to make the VM disk larger
  numCPUs: 2        # increase this number to add vCPUs to your VM
  memoryMiB: 8192   # increase this number to add memory to your VM

Once you have made configuration updates you can apply the changes to your cluster. If you are adding or removing a node, only the terminated nodes will be affected. If you are vertically scaling your nodes, then all nodes will be replaced one at a time.

eksctl anywhere upgrade cluster -f cluster.yaml

Semi-automatic scaling

Scaling your cluster in a semi-automatic way still requires changing your cluster manifest configuration. In a semi-automatic mode you change your cluster spec and then have automation make the cluster changes.

You can do this by storing your cluster config manifest in git and then having a CI/CD system deploy your changes. Or you can use a GitOps controller to apply the changes. To read more about making changes with the integrated Flux GitOps controller you can read how to Manage a cluster with GitOps .

Automatic scaling

Automatic cluster scaling is designed for worker nodes and it is not advised to automatically scale your control plane. Typically, autoscaling is done with a controller such as the Kubernetes Cluster Autoscaler . This has some concerns in an on-prem environment.

Automatic scaling does not work with some providers such as Docker or bare metal. An EKS Anywhere cluster currently is not intended to be used with the Kubernetes Cluster Autoscaler so that it does not interfere with built in controllers or cause unexpected machine thrashing.

In future versions of EKS Anywhere we will be adding support for automatic autoscaling for specific providers.