Adding or removing nodes in a cluster

In Google Distributed Cloud, you add or remove nodes in a cluster by editing the cluster's node pool definitions. You can use the kubectl command to change these definitions.

There are three different kinds of node pools in Google Distributed Cloud: control plane, load balancer, and worker node pools. You edit control plane and load balancer nodes through the definitions in their associated cluster resources, while you edit worker node pool definitions directly.

Viewing node status

You can view the status of nodes and their respective node pools with the kubectl get command.

For example, the following command shows the status of the node pools in the cluster namespace my-cluster:

  kubectl -n my-cluster get nodepools.baremetal.cluster.gke.io

The system returns results similar to the following:

  NAME                    READY   RECONCILING   STALLED   UNDERMAINTENANCE   UNKNOWN
  my-cluster              3       0             0         0                  0
  my-cluster-lb           2       0             0         0                  0
  np1                     3       0             0         0                  0

If you need more information on diagnosing your clusters, see Diagnosing and resetting clusters.

Changing nodes

Most node changes are specified in the cluster config file, which is then applied to the cluster. We recommend you use the cluster config file as the primary source for updating your cluster. It is a best practice to store your config file in a version control system to track changes for troubleshooting purposes. Note that the bmctl update command is supported for standalone clusters only. For admin, user, and hybrid clusters, use kubectl apply to update your cluster with your node pool changes.

The Google Distributed Cloud cluster config file includes a header section with credential information. The credential entries and the rest of the config file are valid YAML, but the credential entries are not valid for the cluster resource. Remove the credential key path entries, such as gcrKeyPath and sshPrivateKeyPath, before using kubectl apply. Use bmctl update credentials for credential updates.

Alternatively, you can use kubectl edit to modify the cluster resource directly. For example:

  kubectl edit cluster -n CLUSTER_NAMESPACE CLUSTER_NAME

The following sections describe some important differences for updating specific node types.

Control plane and load balancer nodes

The control plane and load balancer node pool specifications for Google Distributed Cloud are special. These specifications declare and control critical cluster resources. The canonical source for these resources is their respective sections in the cluster config file:

  • spec.controlPlane.nodePoolSpec
  • spec.LoadBalancer.nodePoolSpec

You add or remove control plane or load balancer nodes by editing the array of addresses under nodes in the corresponding section of the cluster config file.

In a high availability (HA) configuration, an odd number of control plane node pools (three or more) are required to establish a quorum to ensure that if a control plane fails, others will take over. If you have an even number of nodes temporarily while ading or removing nodes for maintenance or replacement, your deployment maintains HA as long as you have enough quorum.

Worker nodes

You can add or remove worker nodes directly with the kubectl command. Worker node pools must have at least one desired node.

In the following example, the command deletes a node pool named np1 where the variable for the cluster namespace is my-cluster:

  kubectl -n my-cluster delete nodepool np1

Similarly, node pools can be resized by editing the spec.nodes array of addresses.

Note that when you remove nodes from a cluster, they are first drained of any pods. Nodes will not be removed from the cluster if pods can't be rescheduled on other nodes. Removing nodes only removes the node from the control plane; the contents of the node are not reset.

The following kubectl edit command lets you edit and then commit changes for the cluster namespace my-cluster and the node pool np1:

  kubectl -n my-cluster edit nodepool np1