Scaling an application

kubectl scale

The kubectl scale command lets your instantaneously change the number of replicas you want to run your application.

To use kubectl scale , you specify the new number of replicas by setting the --replicas flag. For example, to scale my-app to four replicas, run the following command, substituting CONTROLLER for deployment , statefulset , or another controller object type:

 kubectl  
scale  
 CONTROLLER 
  
my-app  
--replicas  
 4 
 

If successful, this command's output should be similar to deployment "my-app" scaled .

Next, run:

 kubectl  
get  
 CONTROLLER 
  
my-app 

The output should look similar to the following:

 NAME                  DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
my-app                4         4         4            4           15m 

kubectl patch

Preview

This feature is subject to the "Pre-GA Offerings Terms" in the General Service Terms section of the Service Specific Terms . Pre-GA features are available "as is" and might have limited support. For more information, see the launch stage descriptions .

Starting in Kubernetes version 1.33 , you can use the kubectl patch command to vertically scale your workload by updating the resources that are assigned to a container, without recreating the Pod. For more information, including limitations, see the Kubernetes documentation for resizing CPU and memory resources .

To use the kubectl patch command, specify the updated resource request under the --patch flag. For example, to scale my-app to 800 mCPUs, run the following command:

 kubectl  
patch  
pod  
my-app  
--subresource  
resize  
--patch  
 \ 
  
 '{"spec":{"containers":[{"name":"pause", "resources":{"requests":{"cpu":"800m"}, "limits":{"cpu":"800m"}}}]}}' 
 

kubectl apply

You can use kubectl apply to apply a new configuration file to an existing controller object. kubectl apply is useful for making multiple changes to a resource, and may be useful for users who prefer to manage their resources in configuration files.

To scale using kubectl apply , the configuration file you supply should include a new number of replicas in the replicas field of the object's specification.

The following is an updated version of the configuration file for the example my-app object. The example shows a Deployment, so if you use another type of controller, such as a StatefulSet, change the kind accordingly. This example works best on a cluster with at least three Nodes.

  apiVersion 
 : 
  
 apps/v1 
 kind 
 : 
  
 Deployment 
 metadata 
 : 
  
 name 
 : 
  
 my-app 
 spec 
 : 
  
 replicas 
 : 
  
 3 
  
 selector 
 : 
  
 matchLabels 
 : 
  
 app 
 : 
  
 app 
  
 template 
 : 
  
 metadata 
 : 
  
 labels 
 : 
  
 app 
 : 
  
 app 
  
 spec 
 : 
  
 containers 
 : 
  
 - 
  
 name 
 : 
  
 my-container 
  
 image 
 : 
  
 us-docker.pkg.dev/google-samples/containers/gke/hello-app:2.0 
 

In this file, the value of the replicas field is 3 . When this configuration file is applied, the object my-app scales to three replicas.

To apply an updated configuration file, run the following command:

 kubectl  
apply  
-f  
config.yaml 

Next, run:

 kubectl  
get  
 CONTROLLER 
  
my-app 

The output should look similar to the following:

 NAME                  DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
my-app                3         3         3            3           15m 

Console

To scale a workload in the Google Cloud console, perform the following steps:

1. Go to the Workloadspage in the Google Cloud console.

   Go to Workloads

2. In the workloads list, click the name of the workload you want to scale.

3. Click list Actions > Scale > Edit replicas.

4. Enter the new number of Replicasfor the workload.

5. Click Scale.

kubectl autoscale

kubectl autoscale creates a HorizontalPodAutoscaler (or HPA) object that targets a specified resource (called the scale target ) and scales it as needed. The HPA periodically adjusts the number of replicas of the scale target to match the average CPU utilization that you specify.

When you use kubectl autoscale , you specify a maximum and minimum number of replicas for your application, as well as a CPU utilization target. For example, to set the maximum number of replicas to six and the minimum to four, with a CPU utilization target of 50% utilization, run the following command:

 kubectl  
autoscale  
deployment  
my-app  
--max  
 6 
  
--min  
 4 
  
--cpu-percent  
 50 
 

In this command, the --max flag is required. The --cpu-percent flag is the target CPU utilization over all the Pods. This command does not immediately scale the Deployment to six replicas, unless there is already a systemic demand.

After running kubectl autoscale , the HorizontalPodAutoscaler object is created and targets the application. When there is a change in load, the object increases or decreases the application's replicas.

To get a list of the HorizontalPodAutoscaler objects in your cluster, run:

 kubectl  
get  
hpa 

To see a specific HorizontalPodAutoscaler object in your cluster, run:

 kubectl  
get  
hpa  
 HPA_NAME 
 

Replace HPA_NAME with the name of your HorizontalPodAutoscaler object.

To see the HorizontalPodAutoscaler configuration:

 kubectl  
get  
hpa  
 HPA_NAME 
  
-o  
yaml 

The output of this command is similar to the following:

  apiVersion 
 : 
  
 v1 
 items 
 : 
 - 
  
 apiVersion 
 : 
  
 autoscaling/v1 
  
 kind 
 : 
  
 HorizontalPodAutoscaler 
  
 metadata 
 : 
  
 creationTimestamp 
 : 
  
 ... 
  
 name 
 : 
  
  HPA_NAME 
 
  
 namespace 
 : 
  
 default 
  
 resourceVersion 
 : 
  
 "664" 
  
 selfLink 
 : 
  
 ... 
  
 uid 
 : 
  
 ... 
  
 spec 
 : 
  
 maxReplicas 
 : 
  
 10 
  
 minReplicas 
 : 
  
 1 
  
 scaleTargetRef 
 : 
  
 apiVersion 
 : 
  
 apps/v1 
  
 kind 
 : 
  
 Deployment 
  
 name 
 : 
  
  HPA_NAME 
 
  
 targetCPUUtilizationPercentage 
 : 
  
 50 
  
 status 
 : 
  
 currentReplicas 
 : 
  
 0 
  
 desiredReplicas 
 : 
  
 0 
 kind 
 : 
  
 List 
 metadata 
 : 
  
 {} 
 resourceVersion 
 : 
  
 "" 
 selfLink 
 : 
  
 "" 
 

In this example output, the targetCPUUtilizationPercentage field holds the 50 percentage value passed in from the kubectl autoscale example.

To see a detailed description of a specific HorizontalPodAutoscaler object in the cluster:

 kubectl  
describe  
hpa  
 HPA_NAME 
 

You can modify the HorizontalPodAutoscaler by applying a new configuration file with kubectl apply , using kubectl edit , or using kubectl patch .

To delete a HorizontalPodAutoscaler object:

 kubectl  
delete  
hpa  
 HPA_NAME 
 

Console

To autoscale a Deployment, perform the following steps:

1. Go to the Workloadspage in the Google Cloud console.

   Go to Workloads

2. In the workloads list, click the name of the Deployment you want to autoscale.

3. Click list Actions > Autoscale.

4. Enter the Maximum number of replicasand, optionally, the Minimum number of replicasfor the Deployment.

5. Under Autoscaling metrics, select and configure metrics as desired.

6. Click Autoscale.