Application Auto Scaling
API Reference (API Version 2016-02-06)


Provides descriptive information about the scalable targets in the specified namespace.

You can filter the results using the ResourceIds and ScalableDimension parameters.

To create a scalable target or update an existing one, see RegisterScalableTarget. If you are no longer using a scalable target, you can deregister it using DeregisterScalableTarget.

Request Syntax

{ "MaxResults": number, "NextToken": "string", "ResourceIds": [ "string" ], "ScalableDimension": "string", "ServiceNamespace": "string" }

Request Parameters

For information about the parameters that are common to all actions, see Common Parameters.

The request accepts the following data in JSON format.


The maximum number of scalable target results. This value can be between 1 and 50. The default value is 50.

If this parameter is used, the operation returns up to MaxResults results at a time, along with a NextToken value. To get the next set of results, include the NextToken value in a subsequent call. If this parameter is not used, the operation returns up to 50 results and a NextToken value, if applicable.

Type: Integer

Required: No


The token for the next set of results.

Type: String

Pattern: [\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*

Required: No


The identifier of the resource associated with the scalable target. This string consists of the resource type and unique identifier. If you specify a scalable dimension, you must also specify a resource ID.

  • ECS service - The resource type is service and the unique identifier is the cluster name and service name. Example: service/default/sample-webapp.

  • Spot fleet request - The resource type is spot-fleet-request and the unique identifier is the Spot fleet request ID. Example: spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE.

  • EMR cluster - The resource type is instancegroup and the unique identifier is the cluster ID and instance group ID. Example: instancegroup/j-2EEZNYKUA1NTV/ig-1791Y4E1L8YI0.

  • AppStream 2.0 fleet - The resource type is fleet and the unique identifier is the fleet name. Example: fleet/sample-fleet.

Type: array of Strings

Length Constraints: Minimum length of 1. Maximum length of 1600.

Pattern: [\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*

Required: No


The scalable dimension associated with the scalable target. This string consists of the service namespace, resource type, and scaling property. If you specify a scalable dimension, you must also specify a resource ID.

  • ecs:service:DesiredCount - The desired task count of an ECS service.

  • ec2:spot-fleet-request:TargetCapacity - The target capacity of a Spot fleet request.

  • elasticmapreduce:instancegroup:InstanceCount - The instance count of an EMR Instance Group.

  • appstream:fleet:DesiredCapacity - The desired capacity of an AppStream 2.0 fleet.

Type: String

Valid Values: ecs:service:DesiredCount | ec2:spot-fleet-request:TargetCapacity | elasticmapreduce:instancegroup:InstanceCount | appstream:fleet:DesiredCapacity

Required: No


The namespace of the AWS service. For more information, see AWS Service Namespaces in the Amazon Web Services General Reference.

Type: String

Valid Values: ecs | elasticmapreduce | ec2 | appstream

Required: Yes

Response Syntax

{ "NextToken": "string", "ScalableTargets": [ { "CreationTime": number, "MaxCapacity": number, "MinCapacity": number, "ResourceId": "string", "RoleARN": "string", "ScalableDimension": "string", "ServiceNamespace": "string" } ] }

Response Elements

If the action is successful, the service sends back an HTTP 200 response.

The following data is returned in JSON format by the service.


The token required to get the next set of results. This value is null if there are no more results to return.

Type: String

Pattern: [\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*


The list of scalable targets that matches the request parameters.

Type: array of ScalableTarget objects


For information about the errors that are common to all actions, see Common Errors.


Concurrent updates caused an exception, for example, if you request an update to an Application Auto Scaling resource that already has a pending update.

HTTP Status Code: 400


The service encountered an internal error.

HTTP Status Code: 400


The next token supplied was invalid.

HTTP Status Code: 400


An exception was thrown for a validation issue. Review the available parameters for the API request.

HTTP Status Code: 400


If you plan to create requests manually, you must replace the Authorization header contents in the examples (AUTHPARAMS) with a signature. For more information, see Signature Version 4 Signing Process in the AWS Gerneral Reference. If you plan to use the AWS CLI or one of the AWS SDKs, these tools sign the requests for you.


The following example describes the scalable targets for the ecs service namespace.

Sample Request

POST / HTTP/1.1 Host: Accept-Encoding: identity Content-Length: 27 X-Amz-Target: AnyScaleFrontendService.DescribeScalableTargets X-Amz-Date: 20160506T184921Z User-Agent: aws-cli/1.10.23 Python/2.7.11 Darwin/15.4.0 botocore/1.4.8 Content-Type: application/x-amz-json-1.1 Authorization: AUTHPARAMS { "ServiceNamespace": "ecs" }

Sample Response

HTTP/1.1 200 OK x-amzn-RequestId: 3f10dab0-13bb-11e6-a873-676fff004c09 Content-Type: application/x-amz-json-1.1 Content-Length: 272 Date: Fri, 06 May 2016 18:49:21 GMT { "ScalableTargets": [ { "CreationTime": 1462558906.199, "MaxCapacity": 10, "MinCapacity": 1, "ResourceId": "service/default/web-app", "RoleARN": "arn:aws:iam::012345678910:role/ApplicationAutoscalingECSRole", "ScalableDimension": "ecs:service:DesiredCount", "ServiceNamespace": "ecs" } ] }

See Also

For more information about using this API in one of the language-specific AWS SDKs, see the following: