Pre-provisioned Add Nodes to Existing Node Pool

This sections covers the prerequisites and procedure you need to scale-up or scale-down nodes in an existing DKP cluster. 

Prerequisites

• You must have the bootstrap node running with the SSH key/secrets created.

• The export values in the environment variables section should contain the addresses of the nodes that you need to add Pre-provisioned: Define Infrastructure.

• Update the preprovisioned_inventory.yaml with the new host addresses.

• Run the kubectl apply command.

Scale up a Cluster Node

Follow these steps:

1. Fetch the existing preprovisioned_inventory:

   CODE

   $ kubectl get preprovisionedinventory

2.  Edit the preprovisioned_inventory to add additional IPs needed for additional worker nodes in the spec.hosts: section: 

   CODE

   $ kubectl edit preprovisionedinventory <preprovisioned_inventory> -n default 

3. Add any additional IPs that you require:

   CODE

   spec: 
       hosts: 
       - address: <worker.ip.add.1> 
       - address: <worker.ip.add.2> 

   After you edit preprovisioned_inventory, fetch the machine deployment. The naming convention with md means that it is for worker machines.
   For example:

   CODE

   $ kubectl --kubeconfig ${CLUSTER_NAME}.conf get machinedeployment 
   NAME                     CLUSTER        AGE     PHASE     REPLICAS   READY   UPDATED   UNAVAILABLE 
   machinedeployment-md-0   cluster-name   9m10s   Running   4          4       4   

4. Scale the worker node to the required number. In this example we are scaling from 4 to 6 worker nodes:

   CODE

   $ kubectl --kubeconfig ${CLUSTER_NAME}.conf scale --replicas=6 machinedeployment machinedeployment-md-0
   
   machinedeployment.cluster.x-k8s.io/machinedeployment-md-0 scaled 

5. Monitor the scaling with this command, by adding -w option to watch:

   CODE

   $ kubectl --kubeconfig ${CLUSTER_NAME}.conf get machinedeployment -w
   
   NAME                     CLUSTER        AGE   PHASE       REPLICAS   READY   UPDATED   UNAVAILABLE 
   machinedeployment-md-0   cluster-name   20m   ScalingUp   6          4       6         2 

6. Also you can check the machine deployment if it is already scaled. The output should resemble this example: 

   CODE

   $ kubectl --kubeconfig ${CLUSTER_NAME}.conf get machinedeployment
   
   NAME                     CLUSTER        AGE     PHASE     REPLICAS   READY   UPDATED   UNAVAILABLE 
   machinedeployment-md-0   cluster-name   3h33m   Running   6          6       6 

7. Alternately, you can use this command and verify the NODENAME column and you should see the additional worker nodes added and in Running state:

   CODE

   $ kubectl --kubeconfig ${CLUSTER_NAME}.conf get machines -o wide
   
   NAME     CLUSTER     AGE     PROVIDERID     PHASE     VERSION     NODENAME

Scale Down a Cluster Node

Follow these steps

1. Run this command on your worker nodes:

   CODE

   kubectl scale machinedeployment <machinedeployment-name> --replicas <new number>

2. For control plane nodes, execute the following command:

   CODE

   kubectl scale kubeadmcontrolplane ${CLUSTER_NAME}-control-plane --replicas <new number>

Additional Notes for Scaling Down

It is possible for machines to get stuck in the provisioning stage when you scaling down. You can utilize a delete operation to clear the stale machine deployment:

kubectl delete machine ${CLUSTER_NAME}-control-plane-<hash>

kubectl delete machine <machinedeployment-name>-<hash>