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This procedure shows you how to remove nodes from a Kubernetes cluster.
Be careful if you are scaling down the master nodes of your cluster. If you have two master nodes and you scale down to have only one master node, then you would have only a single point of failure.
To scale down a Kubernetes cluster:
From a master node of the Kubernetes cluster, use the kubectl get nodes command to see the master and worker nodes of the cluster.
$
kubectl get nodes
NAME STATUS ROLE AGE VERSION master1.example.com Ready master 26h v1.17.x+x.x.x.el7 master2.example.com Ready master 26h v1.17.x+x.x.x.el7 master3.example.com Ready master 26h v1.17.x+x.x.x.el7 master4.example.com Ready master 2m38s v1.17.x+x.x.x.el7 worker1.example.com Ready <none> 26h v1.17.x+x.x.x.el7 worker2.example.com Ready <none> 26h v1.17.x+x.x.x.el7 worker3.example.com Ready <none> 26h v1.17.x+x.x.x.el7 worker4.example.com Ready <none> 2m38s v1.17.x+x.x.x.el7 worker5.example.com Ready <none> 2m38s v1.17.x+x.x.x.el7For this example, there are four master nodes in the Kubernetes cluster:
master1.example.com
master2.example.com
master3.example.com
master4.example.com
There are also five worker nodes in the cluster:
worker1.example.com
worker2.example.com
worker3.example.com
worker4.example.com
worker5.example.com
To update a Kubernetes cluster by scaling it down, use the olcnectl module update command.
For example, to remove the
master4.example.com
master node,worker4.example.com
worker node, andworker5.example.com
worker node from thekubernetes
module namedmycluster
, access the operator node of the Kubernetes cluster and execute the following command:$
olcnectl --api-server 127.0.0.1:8091 module update --environment-name myenvironment \ --name mycluster \ --master-nodes master1.example.com:8090,master2.example.com:8090,master3.example.com:8090 \ --worker-nodes worker1.example.com:8090,worker2.example.com:8090,worker3.example.com:8090
In this example, you are scaling down a Kubernetes cluster so that it has three master nodes and three worker nodes.
In this example, the
master4.example.com
,worker4.example.com
, andworker5.example.com
node are not specified. The Platform API Server keeps track of the nodes of the cluster that it is managing, and knows to scale down the cluster so that these nodes are removed from the cluster.Because three master nodes and three worker nodes are specified in the
–-master-nodes
and–-worker-nodes
options of the olcnectl module update command, the Platform API Server does not remove these nodes from the cluster.Return to a master node of the Kubernetes cluster, and then use the kubectl get nodes command to verify that the cluster is scaled down.
$
kubectl get nodes
NAME STATUS ROLE AGE VERSION master1.example.com Ready master 26h v1.17.x+x.x.x.el7 master2.example.com Ready master 26h v1.17.x+x.x.x.el7 master3.example.com Ready master 26h v1.17.x+x.x.x.el7 worker1.example.com Ready <none> 26h v1.17.x+x.x.x.el7 worker2.example.com Ready <none> 26h v1.17.x+x.x.x.el7 worker3.example.com Ready <none> 26h v1.17.x+x.x.x.el7