第 1 章 Post-installation cluster tasks
After installing OpenShift Container Platform, you can further expand and customize your cluster to your requirements.
1.1. Adjust worker nodes
If you incorrectly sized the worker nodes during deployment, adjust them by creating one or more new machine sets, scale them up, then scale the original machine set down before removing them.
1.1.1. Understanding the difference between machine sets and the machine config pool
MachineSet objects describe OpenShift Container Platform nodes with respect to the cloud or machine provider.
The MachineConfigPool object allows MachineConfigController components to define and provide the status of machines in the context of upgrades.
The MachineConfigPool object allows users to configure how upgrades are rolled out to the OpenShift Container Platform nodes in the machine config pool.
The NodeSelector object can be replaced with a reference to the MachineSet object.
1.1.2. Scaling a machine set manually
If you must add or remove an instance of a machine in a machine set, you can manually scale the machine set.
This guidance is relevant to fully automated, installer-provisioned infrastructure installations. Customized, user-provisioned infrastructure installations does not have machine sets.
Prerequisites
-
Install an OpenShift Container Platform cluster and the
occommand line. -
Log in to
ocas a user withcluster-adminpermission.
Procedure
View the machine sets that are in the cluster:
$ oc get machinesets -n openshift-machine-api
The machine sets are listed in the form of
<clusterid>-worker-<aws-region-az>.Scale the machine set:
$ oc scale --replicas=2 machineset <machineset> -n openshift-machine-api
Or:
$ oc edit machineset <machineset> -n openshift-machine-api
You can scale the machine set up or down. It takes several minutes for the new machines to be available.
1.1.3. The machine set deletion policy
Random, Newest, and Oldest are the three supported deletion options. The default is Random, meaning that random machines are chosen and deleted when scaling machine sets down. The deletion policy can be set according to the use case by modifying the particular machine set:
spec: deletePolicy: <delete_policy> replicas: <desired_replica_count>
Specific machines can also be prioritized for deletion by adding the annotation machine.openshift.io/cluster-api-delete-machine to the machine of interest, regardless of the deletion policy.
By default, the OpenShift Container Platform router pods are deployed on workers. Because the router is required to access some cluster resources, including the web console, do not scale the worker machine set to 0 unless you first relocate the router pods.
Custom machine sets can be used for use cases requiring that services run on specific nodes and that those services are ignored by the controller when the worker machine sets are scaling down. This prevents service disruption.
