Create a step scaling policy using the Amazon CLI - Application Auto Scaling
Register a scalable targetCreate a step scaling policyCreate an alarm that triggers the scaling policyDescribe step scaling policiesDelete a step scaling policy
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Create a step scaling policy using the Amazon CLI

You can create a step scaling policy for Application Auto Scaling by using the Amazon CLI for the following configuration tasks.

Tasks

Register a scalable target

If you haven't already done so, register the scalable target. Use the register-scalable-target command to register a specific resource in the target service as a scalable target. The following example registers an Amazon ECS service with Application Auto Scaling. Application Auto Scaling can scale the number of tasks at a minimum of 2 tasks and a maximum of 10.

Linux, macOS, or Unix

aws application-autoscaling register-scalable-target --service-namespace ecs \
  --scalable-dimension ecs:service:DesiredCount \
  --resource-id service/default/sample-app-service \
  --min-capacity 2 --max-capacity 10

Windows

aws application-autoscaling register-scalable-target --service-namespace ecs --scalable-dimension ecs:service:DesiredCount --resource-id service/default/sample-app-service --min-capacity 2 --max-capacity 10

If successful, this command returns the ARN of the scalable target.

{
    "ScalableTargetARN": "arn:aws-cn:application-autoscaling:region:account-id:scalable-target/1234abcd56ab78cd901ef1234567890ab123"
}
Note

For brevity, the examples in this topic illustrate CLI commands for an Amazon ECS service. To specify a different scalable target, specify its namespace in --service-namespace, its scalable dimension in --scalable-dimension, and its resource ID in --resource-id. For more information and examples for each service, see the topics in Amazon services that you can use with Application Auto Scaling.

Create a step scaling policy

The following is an example step configuration with an adjustment type of ChangeInCapacity that increases the capacity of the scalable target based on the following step adjustments (assuming a CloudWatch alarm threshold of 70 percent):

  • Increase capacity by 1 when the value of the metric is greater than or equal to 70 percent but less than 85 percent

  • Increase capacity by 2 when the value of the metric is greater than or equal to 85 percent but less than 95 percent

  • Increase capacity by 3 when the value of the metric is greater than or equal to 95 percent

Save this configuration in a file named config.json.

{
  "AdjustmentType": "ChangeInCapacity",
  "MetricAggregationType": "Average",
  "Cooldown": 60,
  "StepAdjustments": [ 
    {
      "MetricIntervalLowerBound": 0,
      "MetricIntervalUpperBound": 15,
      "ScalingAdjustment": 1
    },
    {
      "MetricIntervalLowerBound": 15,
      "MetricIntervalUpperBound": 25,
      "ScalingAdjustment": 2
    },
    {
      "MetricIntervalLowerBound": 25,
      "ScalingAdjustment": 3
    }
  ]
}

Use the following put-scaling-policy command, along with the config.json file that you created, to create a scaling policy named my-step-scaling-policy.

Linux, macOS, or Unix

aws application-autoscaling put-scaling-policy --service-namespace ecs \
  --scalable-dimension ecs:service:DesiredCount \
  --resource-id service/default/sample-app-service \
  --policy-name my-step-scaling-policy --policy-type StepScaling \
  --step-scaling-policy-configuration file://config.json

Windows

aws application-autoscaling put-scaling-policy --service-namespace ecs --scalable-dimension ecs:service:DesiredCount --resource-id service/default/sample-app-service --policy-name my-step-scaling-policy --policy-type StepScaling --step-scaling-policy-configuration file://config.json

The output includes the ARN that serves as a unique name for the policy. You need it to create CloudWatch alarms.

{
    "PolicyARN": "arn:aws-cn:autoscaling:region:123456789012:scalingPolicy:ac542982-cbeb-4294-891c-a5a941dfa787:resource/ecs/service/default/sample-app-service:policyName/my-step-scaling-policy"
}

Create an alarm that triggers the scaling policy

Finally, use the following CloudWatch put-metric-alarm command to create an alarm to use with your step scaling policy. In this example, you have an alarm based on average CPU utilization. The alarm is configured to be in an ALARM state if it reaches a threshold of 70 percent for at least two consecutive evaluation periods of 60 seconds. To specify a different CloudWatch metric or use your own custom metric, specify its name in --metric-name and its namespace in --namespace.

Linux, macOS, or Unix

aws cloudwatch put-metric-alarm --alarm-name Step-Scaling-AlarmHigh-ECS:service/default/sample-app-service \
  --metric-name CPUUtilization --namespace AWS/ECS --statistic Average \
  --period 60 --evaluation-periods 2 --threshold 70 \
  --comparison-operator GreaterThanOrEqualToThreshold \
  --dimensions Name=ClusterName,Value=default Name=ServiceName,Value=sample-app-service \
  --alarm-actions PolicyARN

Windows

aws cloudwatch put-metric-alarm --alarm-name Step-Scaling-AlarmHigh-ECS:service/default/sample-app-service --metric-name CPUUtilization --namespace AWS/ECS --statistic Average --period 60 --evaluation-periods 2 --threshold 70 --comparison-operator GreaterThanOrEqualToThreshold --dimensions Name=ClusterName,Value=default Name=ServiceName,Value=sample-app-service --alarm-actions PolicyARN

Describe step scaling policies

You can describe all scaling policies for the specified service namespace using the following describe-scaling-policies command.

aws application-autoscaling describe-scaling-policies --service-namespace ecs

You can filter the results to just the step scaling policies using the --query parameter. For more information about the syntax for query, see Controlling command output from the Amazon CLI in the Amazon Command Line Interface User Guide.

Linux, macOS, or Unix

aws application-autoscaling describe-scaling-policies --service-namespace ecs \
  --query 'ScalingPolicies[?PolicyType==`StepScaling`]'

Windows

aws application-autoscaling describe-scaling-policies --service-namespace ecs --query "ScalingPolicies[?PolicyType==`StepScaling`]"

The following is example output.

[
    {
        "PolicyARN": "PolicyARN",
        "StepScalingPolicyConfiguration": {
            "MetricAggregationType": "Average",
            "Cooldown": 60,
            "StepAdjustments": [
                {
                    "MetricIntervalLowerBound": 0.0,
                    "MetricIntervalUpperBound": 15.0,
                    "ScalingAdjustment": 1
                },
                {
                    "MetricIntervalLowerBound": 15.0,
                    "MetricIntervalUpperBound": 25.0,
                    "ScalingAdjustment": 2
                },
                {
                    "MetricIntervalLowerBound": 25.0,
                    "ScalingAdjustment": 3
                }
            ],
            "AdjustmentType": "ChangeInCapacity"
        },
        "PolicyType": "StepScaling",
        "ResourceId": "service/default/sample-app-service",
        "ServiceNamespace": "ecs",
        "Alarms": [
            {
                "AlarmName": "Step-Scaling-AlarmHigh-ECS:service/default/sample-app-service",
                "AlarmARN": "arn:aws-cn:cloudwatch:region:012345678910:alarm:Step-Scaling-AlarmHigh-ECS:service/default/sample-app-service"
            }
        ],
        "PolicyName": "my-step-scaling-policy",
        "ScalableDimension": "ecs:service:DesiredCount",
        "CreationTime": 1515024099.901
    }
]

Delete a step scaling policy

When you no longer need a step scaling policy, you can delete it. To delete both the scaling policy and the CloudWatch alarm, complete the following tasks.

To delete your scaling policy

Use the following delete-scaling-policy command.

Linux, macOS, or Unix

aws application-autoscaling delete-scaling-policy --service-namespace ecs \
  --scalable-dimension ecs:service:DesiredCount \
  --resource-id service/default/sample-app-service \
  --policy-name my-step-scaling-policy

Windows

aws application-autoscaling delete-scaling-policy --service-namespace ecs --scalable-dimension ecs:service:DesiredCount --resource-id service/default/sample-app-service --policy-name my-step-scaling-policy
To delete the CloudWatch alarm

Use the delete-alarms command. You can delete one or more alarms at a time. For example, use the following command to delete the Step-Scaling-AlarmHigh-ECS:service/default/sample-app-service and Step-Scaling-AlarmLow-ECS:service/default/sample-app-service alarms.

aws cloudwatch delete-alarms --alarm-name Step-Scaling-AlarmHigh-ECS:service/default/sample-app-service Step-Scaling-AlarmLow-ECS:service/default/sample-app-service