Creating MachinePools

Cluster API Provider AWS (CAPA) has experimental support for managed ROSA MachinePools through the infrastructure type ROSAMachinePool. A ROSAMachinePool is responsible for orchestrating and bootstraping a group of EC2 machines into kubernetes nodes.

Using clusterctl to deploy

To deploy a MachinePool / ROSAMachinePool via clusterctl generate use the template located here.

Make sure to set up your environment as described here.

clusterctl generate cluster my-cluster --from templates/cluster-template-rosa-machinepool > my-cluster.yaml

Example

Below is an example of the resources needed to create a ROSA MachinePool.

---
apiVersion: cluster.x-k8s.io/v1beta1
kind: MachinePool
metadata:
  name: "${CLUSTER_NAME}-pool-0"
spec:
  clusterName: "${CLUSTER_NAME}"
  replicas: 1
  template:
    spec:
      clusterName: "${CLUSTER_NAME}"
      bootstrap:
        dataSecretName: ""
      infrastructureRef:
        name: "${CLUSTER_NAME}-pool-0"
        apiVersion: infrastructure.cluster.x-k8s.io/v1beta2
        kind: ROSAMachinePool
---
apiVersion: infrastructure.cluster.x-k8s.io/v1beta2
kind: ROSAMachinePool
metadata:
  name: "${CLUSTER_NAME}-pool-0"
spec:
  nodePoolName: "nodepool-0"
  instanceType: "m7i.xlarge"
  subnet: "${PRIVATE_SUBNET_ID}"
  version: "${OPENSHIFT_VERSION}"

Note: m7i.xlarge is not available in all AWS regions. Choose an instance type available in your target region.

Spot Instances

Setting spotMarketOptions runs the MachinePool’s nodes on AWS Spot instances, which cost less than on-demand instances but can be reclaimed by AWS at any time.

The simplest form bids the on-demand price, so you pay no more than you would for on-demand capacity while still benefiting from lower Spot pricing:

apiVersion: infrastructure.cluster.x-k8s.io/v1beta2
kind: ROSAMachinePool
metadata:
  name: "${CLUSTER_NAME}-pool-0"
spec:
  nodePoolName: "nodepool-0"
  instanceType: "m7i.xlarge"
  subnet: "${PRIVATE_SUBNET_ID}"
  version: "${OPENSHIFT_VERSION}"
  spotMarketOptions: {}

To cap the hourly bid instead, set maxPrice:

  spotMarketOptions:
    maxPrice: "0.5"

maxPrice accepts either a price in USD per hour or the string "on-demand", and defaults to "on-demand" when omitted. A numeric price must be greater than zero, so "0" and "0.0" are rejected. Setting maxPrice below the current Spot price means the node pool will not get capacity.

Constraints

spotMarketOptions cannot be added to or removed from an existing MachinePool. Whether a node pool uses Spot instances is fixed when it is created; switching requires replacing the MachinePool.

It also cannot be combined with capacityReservationID, since a capacity reservation applies to on-demand instances.

Changing the price later

maxPrice is the one part of spotMarketOptions that can be changed after creation, and only in one direction:

Once a numeric maxPrice is set it cannot be returned to "on-demand" — the ROSA API rejects clearing the bid, so the change is refused by the ROSAMachinePool webhook rather than failing later during reconciliation. Removing the maxPrice field is treated the same way as setting it back to "on-demand". To go back to on-demand pricing, replace the MachinePool.

see ROSAMachinePool CRD Reference for all possible configurations.