Resizing a cluster

Standard

This page explains how to resize clusters. You can resize a cluster to increase or decrease the number of nodes in that cluster. To learn how to add node pools and manage your existing node pools, refer to Adding and managing node pools.

When you add or remove nodes in your cluster, Google Kubernetes Engine (GKE) adds or removes the associated virtual machine (VM) instances from the underlying Compute Engine Managed Instance Groups (MIGs) provisioned for your node pools.

Increasing the size of your cluster

When you increase the size of a cluster:

New node instances are created using the same configuration as the existing instances
New Pods may be scheduled onto the new instances
Existing Pods are not moved onto the new instances

When you increase the size of a node pool that spans multiple zones, the new size represents the number of nodes in the node pool per zone. For example, if you have a node pool of size 2 spanning two zones, the total node count is 4. If you resize the node pool to size 4, the total node count becomes 8.

Decreasing the size of your cluster

When you decrease the size of a cluster:

The Pods that are scheduled on the instances being removed are killed
Pods managed by a replication controller are rescheduled by the controller onto the remaining instances
Pods not managed by a replication controller are not restarted

The MIG does not differentiate between instances running Pods and instances without Pods. Resizing down removes instances at random.

Before you begin

Before you start, make sure you have performed the following tasks:

Ensure that you have enabled the Google Kubernetes Engine API.

Enable Google Kubernetes Engine API

Ensure that you have installed the Cloud SDK.

Set up default gcloud settings using one of the following methods:

Using gcloud init, if you want to be walked through setting defaults.
Using gcloud config, to individually set your project ID, zone, and region.

Using gcloud init

If you receive the error One of [--zone, --region] must be supplied: Please specify location, complete this section.

Run gcloud init and follow the directions:
```
gcloud init
```
If you are using SSH on a remote server, use the --console-only flag to prevent the command from launching a browser:
```
gcloud init --console-only
```
Follow the instructions to authorize gcloud to use your Google Cloud account.
Create a new configuration or select an existing one.
Choose a Google Cloud project.
Choose a default Compute Engine zone for zonal clusters or a region for regional or Autopilot clusters.

Note: You can override these default settings in gcloud commands using the --project, --zone, and --region flags.

Using gcloud config

Set your default project ID:
```
gcloud config set project PROJECT_ID
```
If you are working with zonal clusters, set your default compute zone:
```
gcloud config set compute/zone COMPUTE_ZONE
```
If you are working with Autopilot or regional clusters, set your default compute region:
```
gcloud config set compute/region COMPUTE_REGION
```
Update gcloud to the latest version:
```
gcloud components update
```

Note: You can override these default settings in gcloud commands using the --project, --zone, and --region flags.

Resize a cluster

gcloud

To resize a cluster's node pools, run the gcloud container clusters resize command:

gcloud container clusters resize CLUSTER_NAME --node-pool POOL_NAME \
    --num-nodes NUM_NODES

Replace the following:

CLUSTER_NAME: the name of the cluster to resize.
POOL_NAME: the name of the node pool to resize.
NUM_NODES: the number of nodes in the pool in a zonal cluster. If you use multi-zonal or regional clusters, NUM_NODES is the number of nodes for each zone the node pools is in.

Repeat this command for each node pool. If your cluster has only one node pool, omit the --node-pool flag.

Console

To resize a cluster's node pools, perform the following steps:

Go to the Google Kubernetes Engine page in Cloud Console.

Go to Google Kubernetes Engine
Beside the cluster you want to edit, click Actions, then click Edit.
Click the Nodes tab next to the Details tab.
In the Node Pools section, click the name of the node pool that you want to resize.
Click Resize.
In the Number of nodes field, enter how many nodes that you want in the node pool, and then click Resize.
Repeat for each node pool as needed.

Decrease the size of your cluster with drain

You can manually decrease the size of your cluster and drain each instance's Pods before they are removed.

To learn how to add node pools and to manage existing ones, refer to Adding and managing node pools.

To decrease and drain your cluster, run the gcloud container clusters resize command:

gcloud container clusters resize CLUSTER_NAME --node-pool POOL_NAME \
  --num-nodes NUM_NODES

Replace the following:

CLUSTER_NAME: the name of the cluster to resize.
POOL_NAME: the name of the node pool to resize.
NUM_NODES: the number of nodes in the pool in a zonal cluster. If you use multi-zonal or regional clusters, NUM_NODES is the number of nodes for each zone the node pools is in.

Autoscaling a cluster

GKE's cluster autoscaler feature automatically resizes your node pools in response to changing conditions, such as changes in your workloads and resource usage.

To learn more about how autoscaling works, refer to the cluster autoscaler documentation. To set up autoscaling for your cluster, see Autoscaling a cluster.

What's next

Learn more about clusters.