Prerequisites

Before you begin, you must:

Replace a worker node

In certain situations, you may want to delete a worker node and have Cluster API replace it with a newly provisioned machine.

  1. Identify the name of the node to delete.

    List the nodes:

    kubectl --kubeconfig ${CLUSTER_NAME}.conf get nodes
    CODE

    The output from this command resembles the following:

    NAME                                         STATUS   ROLES                  AGE   VERSION
    ip-10-0-100-85.us-west-2.compute.internal    Ready    <none>                 16m   v1.22.8
    ip-10-0-106-183.us-west-2.compute.internal   Ready    control-plane,master   15m   v1.22.8
    ip-10-0-158-104.us-west-2.compute.internal   Ready    control-plane,master   17m   v1.22.8
    ip-10-0-203-138.us-west-2.compute.internal   Ready    control-plane,master   16m   v1.22.8
    ip-10-0-70-169.us-west-2.compute.internal    Ready    <none>                 16m   v1.22.8
    ip-10-0-77-176.us-west-2.compute.internal    Ready    <none>                 16m   v1.22.8
    ip-10-0-96-61.us-west-2.compute.internal     Ready    <none>                 16m   v1.22.8
    CODE

  2. Export a variable with the node name to use in the next steps:

    This example uses the name ip-10-0-100-85.us-west-2.compute.internal.

    export NAME_NODE_TO_DELETE="<ip-10-0-100-85.us-west-2.compute.internal>"
    CODE

  3. Delete the Machine resource

    export NAME_MACHINE_TO_DELETE=$(kubectl --kubeconfig ${CLUSTER_NAME}.conf get machine -ojsonpath="{.items[?(@.status.nodeRef.name==\"$NAME_NODE_TO_DELETE\")].metadata.name}")
    kubectl --kubeconfig ${CLUSTER_NAME}.conf delete machine "$NAME_MACHINE_TO_DELETE"
    CODE

    machine.cluster.x-k8s.io "aws-example-1-md-0-cb9c9bbf7-t894m" deleted
    CODE

    The command will not return immediately. It will return once the Machine resource has been deleted.

    A few minutes after the Machine resource is deleted, the corresponding Node resource is also deleted.

  4. Observe that the Machine resource is being replaced using this command:

    kubectl --kubeconfig ${CLUSTER_NAME}.conf get machinedeployment
    CODE

    NAME               CLUSTER       REPLICAS   READY   UPDATED   UNAVAILABLE   PHASE       AGE     VERSION
    aws-example-md-0   aws-example   4          3       4         1             ScalingUp   7m53s   v1.22.8
    CODE

    In this example, there are two replicas, but only 1 is ready. One replica is unavailable, and the ScalingUp phase means a new Machine is being created.

  5. Identify the replacement Machine using this command:

    export NAME_NEW_MACHINE=$(kubectl --kubeconfig ${CLUSTER_NAME}.conf get machines \
        -l=cluster.x-k8s.io/deployment-name=${CLUSTER_NAME}-md-0 \
        -ojsonpath='{.items[?(@.status.phase=="Running")].metadata.name}{"\n"}')
    echo "$NAME_NEW_MACHINE"
    CODE

    aws-example-md-0-cb9c9bbf7-hcl8z aws-example-md-0-cb9c9bbf7-rtdqw aws-example-md-0-cb9c9bbf7-td29r aws-example-md-0-cb9c9bbf7-w64kg
    CODE

    If the output is empty, the new Machine has probably exited the Provisioning phase and entered the Running phase.

  6. Identify the replacement Node using this command:

    kubectl --kubeconfig ${CLUSTER_NAME}.conf get nodes 
    CODE

    NAME                                         STATUS   ROLES                  AGE   VERSION
    ip-10-0-106-183.us-west-2.compute.internal   Ready    control-plane,master   20m   v1.22.8
    ip-10-0-158-104.us-west-2.compute.internal   Ready    control-plane,master   23m   v1.22.8
    ip-10-0-203-138.us-west-2.compute.internal   Ready    control-plane,master   22m   v1.22.8
    ip-10-0-70-169.us-west-2.compute.internal    Ready    <none>                 22m   v1.22.8
    ip-10-0-77-176.us-west-2.compute.internal    Ready    <none>                 22m   v1.22.8
    ip-10-0-86-58.us-west-2.compute.internal     Ready    <none>                 57s   v1.22.8
    ip-10-0-96-61.us-west-2.compute.internal     Ready    <none>                 22m   v1.22.8
    CODE

    If the output is empty, the Node resource is not yet available, or does not yet have the expected annotation. Wait a few minutes, then repeat the command.