1.7. About the machine autoscaler
The machine autoscaler adjusts the number of Machines in the machine sets that you deploy in an OpenShift Container Platform cluster. You can scale both the default worker machine set and any other machine sets that you create. The machine autoscaler makes more Machines when the cluster runs out of resources to support more deployments. Any changes to the values in MachineAutoscaler resources, such as the minimum or maximum number of instances, are immediately applied to the machine set they target.
You must deploy a machine autoscaler for the cluster autoscaler to scale your machines. The cluster autoscaler uses the annotations on machine sets that the machine autoscaler sets to determine the resources that it can scale. If you define a cluster autoscaler without also defining machine autoscalers, the cluster autoscaler will never scale your cluster.
1.7.1. MachineAutoscaler resource definition
This MachineAutoscaler resource definition shows the parameters and sample values for the machine autoscaler.
apiVersion: "autoscaling.openshift.io/v1beta1" kind: "MachineAutoscaler" metadata: name: "worker-us-east-1a" 1 namespace: "openshift-machine-api" spec: minReplicas: 1 2 maxReplicas: 12 3 scaleTargetRef: 4 apiVersion: machine.openshift.io/v1beta1 kind: MachineSet 5 name: worker-us-east-1a 6
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- Specify the machine autoscaler name. To make it easier to identify which machine set this machine autoscaler scales, specify or include the name of the machine set to scale. The machine set name takes the following form:
<clusterid>-<machineset>-<aws-region-az> - 2
- Specify the minimum number machines of the specified type that must remain in the specified zone after the cluster autoscaler initiates cluster scaling. If running in AWS, GCP, or Azure, this value can be set to
0. For other providers, do not set this value to0. - 3
- Specify the maximum number machines of the specified type that the cluster autoscaler can deploy in the specified AWS zone after it initiates cluster scaling. Ensure that the
maxNodesTotalvalue in theClusterAutoscalerresource definition is large enough to allow the machine autoscaler to deploy this number of machines. - 4
- In this section, provide values that describe the existing machine set to scale.
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- The
kindparameter value is alwaysMachineSet. - 6
- The
namevalue must match the name of an existing machine set, as shown in themetadata.nameparameter value.
1.7.2. Deploying the machine autoscaler
To deploy the machine autoscaler, you create an instance of the MachineAutoscaler resource.
Procedure
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Create a YAML file for the
MachineAutoscalerresource that contains the customized resource definition. Create the resource in the cluster:
$ oc create -f <filename>.yaml 1- 1
<filename>is the name of the resource file that you customized.
