# Defining a scaling policy A target-tracking scaling policy configuration is represented by a JSON block that the metrics and target values are defined in. You can save a scaling policy configuration as a JSON block in a text file. You use that text file when invoking the AWS CLI or the Application Auto Scaling API. For more information about policy configuration syntax, see [TargetTrackingScalingPolicyConfiguration](https://docs.aws.amazon.com/ApplicationAutoScaling/latest/APIReference/API_TargetTrackingScalingPolicyConfiguration.html) in the *Application Auto Scaling API Reference*. The following options are available for defining a target-tracking scaling policy configuration: **Topics** + [Using a predefined metric](#AutoScaling-Predefined-Metric) + [Editing a scaling policy](AutoScaling-Editing-Policy.md) + [Deleting a scaling policy](AutoScaling-Deleting-Policy.md) + [Use CloudFormation for Auto Scaling policies](AutoScaling-with-Cloudformation.md) + [Scheduled scaling](AutoScaling-with-Scheduled-Scaling-Replicas.md) ## Using a predefined metric A target-tracking scaling policy configuration is represented by a JSON block that the metrics and target values are defined in. You can save a scaling policy configuration as a JSON block in a text file. You use that text file when invoking the AWS CLI or the Application Auto Scaling API. For more information about policy configuration syntax, see [TargetTrackingScalingPolicyConfiguration](https://docs.aws.amazon.com/ApplicationAutoScaling/latest/APIReference/API_TargetTrackingScalingPolicyConfiguration.html) in the *Application Auto Scaling API Reference*. The following options are available for defining a target-tracking scaling policy configuration: **Topics** + [Using a predefined metric](#AutoScaling-Predefined-Metric) + [Using a custom metric](#AutoScaling-Custom-Metric) + [Using cooldown periods](#AutoScaling-Using-Cooldowns) + [Disabling scale-in activity](#AutoScaling-Disabling-Scalein) + [Applying a scaling policy to an ElastiCache for Valkey and Redis OSS cluster](#AutoScaling-Applying-Policy) ### Using a predefined metric By using predefined metrics, you can quickly define a target-tracking scaling policy for an ElastiCache for Valkey and Redis OSS cluster that works with target tracking in ElastiCache Auto Scaling. Currently, ElastiCache supports the following predefined metric in ElastiCache Replicas Auto Scaling: `ElastiCacheReplicaEngineCPUUtilization` – The average value of the EngineCPUUtilization metric in CloudWatch across all replicas in the cluster. You can find the aggregated metric value in CloudWatch under ElastiCache `ReplicationGroupId, Role` for required ReplicationGroupId and Role Replica. To use a predefined metric in your scaling policy, you create a target tracking configuration for your scaling policy. This configuration must include a `PredefinedMetricSpecification` for the predefined metric and a `TargetValue` for the target value of that metric. ### Using a custom metric By using custom metrics, you can define a target-tracking scaling policy that meets your custom requirements. You can define a custom metric based on any ElastiCache for Valkey and Redis OSS metric that changes in proportion to scaling. Not all ElastiCache metrics work for target tracking. The metric must be a valid utilization metric and describe how busy an instance is. The value of the metric must increase or decrease in proportion to the number of replicas in the cluster. This proportional increase or decrease is necessary to use the metric data to proportionally increase or decrease the number of replicas. **Example** The following example describes a target-tracking configuration for a scaling policy. In this configuration, a custom metric adjusts a cluster based on an average CPU utilization of 50 percent across all replicas in an cluster named `my-db-cluster`. ``` {"TargetValue": 50, "CustomizedMetricSpecification": {"MetricName": "EngineCPUUtilization", "Namespace": "AWS/ElastiCache", "Dimensions": [ {"Name": "ReplicationGroup","Value": "my-db-cluster"}, {"Name": "Role","Value": "REPLICA"} ], "Statistic": "Average", "Unit": "Percent" } } ``` ### Using cooldown periods You can specify a value, in seconds, for `ScaleOutCooldown` to add a cooldown period for scaling out your cluster. Similarly, you can add a value, in seconds, for `ScaleInCooldown` to add a cooldown period for scaling in your cluster. For more information about `ScaleInCooldown` and `ScaleOutCooldown`, see [TargetTrackingScalingPolicyConfiguration](https://docs.aws.amazon.com/ApplicationAutoScaling/latest/APIReference/API_TargetTrackingScalingPolicyConfiguration.html) in the *Application Auto Scaling API Reference*. The following example describes a target-tracking configuration for a scaling policy. In this configuration, the `ElastiCacheReplicaEngineCPUUtilization`predefined metric is used to adjust a cluster based on an average CPU utilization of 40 percent across all replicas in that cluster. The configuration provides a scale-in cooldown period of 10 minutes and a scale-out cooldown period of 5 minutes. ``` {"TargetValue": 40.0, "PredefinedMetricSpecification": {"PredefinedMetricType": "ElastiCacheReplicaEngineCPUUtilization" }, "ScaleInCooldown": 600, "ScaleOutCooldown": 300 } ``` ### Disabling scale-in activity You can prevent the target-tracking scaling policy configuration from scaling in your ElastiCache for Valkey and Redis OSS cluster by disabling scale-in activity. Disabling scale-in activity prevents the scaling policy from deleting replicas, while still allowing the scaling policy to add them as needed. You can specify a Boolean value for `DisableScaleIn` to enable or disable scale in activity for your cluster. For more information about `DisableScaleIn`, see [TargetTrackingScalingPolicyConfiguration](https://docs.aws.amazon.com/ApplicationAutoScaling/latest/APIReference/API_TargetTrackingScalingPolicyConfiguration.html) in the *Application Auto Scaling API Reference*. **Example** The following example describes a target-tracking configuration for a scaling policy. In this configuration, the `ElastiCacheReplicaEngineCPUUtilization` predefined metric adjusts a cluster based on an average CPU utilization of 40 percent across all replicas in that cluster. The configuration disables scale-in activity for the scaling policy. ``` {"TargetValue": 40.0, "PredefinedMetricSpecification": {"PredefinedMetricType": "ElastiCacheReplicaEngineCPUUtilization" }, "DisableScaleIn": true } ``` ### Applying a scaling policy to an ElastiCache for Valkey and Redis OSS cluster After registering your cluster with ElastiCache for Valkey and Redis OSS auto scaling and defining a scaling policy, you apply the scaling policy to the registered cluster. To apply a scaling policy to an ElastiCache for Valkey and Redis OSS cluster, you can use the AWS CLI or the Application Auto Scaling API. **Using the AWS CLI** To apply a scaling policy to your ElastiCache for Valkey and Redis OSS cluster, use the [put-scaling-policy](https://docs.aws.amazon.com/cli/latest/reference/autoscaling/put-scaling-policy.html) command with the following parameters: + --policy-name – The name of the scaling policy. + --policy-type – Set this value to `TargetTrackingScaling`. + --resource-id – The resource identifier for the cluster. For this parameter, the resource type is ReplicationGroup and the unique identifier is the name of the cluster, for example `replication-group/myscalablecluster`. + --service-namespace – Set this value to elasticache. + --scalable-dimension – Set this value to `elasticache:replication-group:Replicas`. + --target-tracking-scaling-policy-configuration – The target-tracking scaling policy configuration to use for the cluster. **Example** In the following example, you apply a target-tracking scaling policy named `myscalablepolicy` to a cluster named `myscalablecluster` with ElastiCache auto scaling. To do so, you use a policy configuration saved in a file named `config.json`. For Linux, macOS, or Unix: ``` aws application-autoscaling put-scaling-policy \ --policy-name myscalablepolicy \ --policy-type TargetTrackingScaling \ --resource-id replication-group/myscalablecluster \ --service-namespace elasticache \ --scalable-dimension elasticache:replication-group:Replicas \ --target-tracking-scaling-policy-configuration file://config.json ``` ``` {"TargetValue": 40.0, "PredefinedMetricSpecification": {"PredefinedMetricType": "ElastiCacheReplicaEngineCPUUtilization" }, "DisableScaleIn": true } ``` For Windows: ``` aws application-autoscaling put-scaling-policy ^ --policy-name myscalablepolicy ^ --policy-type TargetTrackingScaling ^ --resource-id replication-group/myscalablecluster ^ --service-namespace elasticache ^ --scalable-dimension elasticache:replication-group:Replicas ^ --target-tracking-scaling-policy-configuration file://config.json ``` **Using the API** To apply a scaling policy to your ElastiCache cluster with the Application Auto Scaling API, use the [PutScalingPolicy](https://docs.aws.amazon.com/autoscaling/application/APIReference/API_PutScalingPolicy.html) Application Auto Scaling API operation with the following parameters: + PolicyName – The name of the scaling policy. + PolicyType – Set this value to `TargetTrackingScaling`. + ResourceID – The resource identifier for the cluster. For this parameter, the resource type is ReplicationGroup and the unique identifier is the name of the ElastiCache for Redis OSS cluster, for example `replication-group/myscalablecluster`. + ServiceNamespace – Set this value to elasticache. + ScalableDimension – Set this value to `elasticache:replication-group:Replicas`. + TargetTrackingScalingPolicyConfiguration – The target-tracking scaling policy configuration to use for the cluster. **Example** In the following example, you apply a target-tracking scaling policy named `scalablepolicy` to an cluster named `myscalablecluster` with ElastiCache auto scaling. You use a policy configuration based on the `ElastiCacheReplicaEngineCPUUtilization` predefined metric. ``` POST / HTTP/1.1 Host: autoscaling.us-east-2.amazonaws.com Accept-Encoding: identity Content-Length: 219 X-Amz-Target: AnyScaleFrontendService.PutScalingPolicy X-Amz-Date: 20160506T182145Z 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 { "PolicyName": "myscalablepolicy", "ServiceNamespace": "elasticache", "ResourceId": "replication-group/myscalablecluster", "ScalableDimension": "elasticache:replication-group:Replicas", "PolicyType": "TargetTrackingScaling", "TargetTrackingScalingPolicyConfiguration": { "TargetValue": 40.0, "PredefinedMetricSpecification": { "PredefinedMetricType": "ElastiCacheReplicaEngineCPUUtilization" } } } ``` # Editing a scaling policy You can edit a scaling policy using the AWS Management Console, the AWS CLI, or the Application Auto Scaling API. **Editing a scaling policy using the AWS Management Console** You can only edit policies with type Predefined metrics by using the AWS Management Console 1. Sign in to the AWS Management Console and open the Amazon ElastiCache console at [https://console.aws.amazon.com/elasticache/](https://console.aws.amazon.com/elasticache/). 1. In the navigation pane, choose **Valkey** or **Redis OSS** 1. Choose the cluster that you want to add a policy to (choose the cluster name and not the button to its left). 1. Choose the **Auto Scaling policies** tab. 1. Under **Scaling policies**, choose the button to the left of the Auto Scaling policy you wish to change, and then choose **Modify**. 1. Make the requisite changes to the policy. 1. Choose **Modify**. 1. Make changes to the policy. 1. Choose **Modify**. **Editing a scaling policy using the AWS CLI or the Application Auto Scaling API ** You can use the AWS CLI or the Application Auto Scaling API to edit a scaling policy in the same way that you apply a scaling policy: + When using the Application Auto Scaling API, specify the name of the policy you want to edit in the `PolicyName` parameter. Specify new values for the parameters you want to change. For more information, see [Applying a scaling policy to an ElastiCache for Valkey and Redis OSS cluster](AutoScaling-Defining-Policy.md#AutoScaling-Applying-Policy). # Deleting a scaling policy You can delete a scaling policy using the AWS Management Console, the AWS CLI or the Application Auto Scaling API **Deleting a scaling policy using the AWS Management Console** You can only edit policies with type Predefined metrics by using the AWS Management Console 1. Sign in to the AWS Management Console and open the Amazon ElastiCache console at [https://console.aws.amazon.com/elasticache/](https://console.aws.amazon.com/elasticache/). 1. In the navigation pane, choose **Valkey** or **Redis OSS** 1. Choose the cluster whose auto scaling policy you want to delete. 1. Choose the **Auto Scaling policies** tab. 1. Under **Scaling policies**, choose the auto scaling policy, and then choose **Delete**. **Deleting a scaling policy using the AWS CLI or the Application Auto Scaling API ** You can use the AWS CLI or the Application Auto Scaling API to delete a scaling policy from an ElastiCache cluster. **CLI** To delete a scaling policy from your ElastiCache for Valkey and Redis OSS cluster, use the [delete-scaling-policy](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/delete-scaling-policy.html) command with the following parameters: + --policy-name – The name of the scaling policy. + --resource-id – The resource identifier for the cluster. For this parameter, the resource type is ReplicationGroup and the unique identifier is the name of the cluster, for example `replication-group/myscalablecluster`. + --service-namespace – Set this value to elasticache. + --scalable-dimension – Set this value to `elasticache:replication-group:Replicas`. **Example** In the following example, you delete a target-tracking scaling policy named `myscalablepolicy` from an ELC; cluster named `myscalablecluster`. For Linux, macOS, or Unix: ``` aws application-autoscaling delete-scaling-policy \ --policy-name myscalablepolicy \ --resource-id replication-group/myscalablecluster \ --service-namespace elasticache \ --scalable-dimension elasticache:replication-group:Replicas \ ``` For Windows: ``` aws application-autoscaling delete-scaling-policy ^ --policy-name myscalablepolicy ^ --resource-id replication-group/myscalablecluster ^ --service-namespace elasticache ^ --scalable-dimension elasticache:replication-group:Replicas ^ ``` **API** To delete a scaling policy from your ElastiCache for Valkey and Redis OSS cluster, use the [DeleteScalingPolicy](https://docs.aws.amazon.com/ApplicationAutoScaling/latest/APIReference/API_DeleteScalingPolicy.html) Application Auto Scaling API operation with the following parameters: + PolicyName – The name of the scaling policy. + ResourceID – The resource identifier for the cluster. For this parameter, the resource type is ReplicationGroup and the unique identifier is the name of the cluster, for example `replication-group/myscalablecluster`. + ServiceNamespace – Set this value to elasticache. + ScalableDimension – Set this value to `elasticache:replication-group:Replicas`. In the following example, you delete a target-tracking scaling policy named `myscalablepolicy` from a cluster named `myscalablecluster` with the Application Auto Scaling API. ``` POST / HTTP/1.1 >>>>>>> mainline Host: autoscaling.us-east-2.amazonaws.com Accept-Encoding: identity Content-Length: 219 X-Amz-Target: AnyScaleFrontendService.DeleteScalingPolicy X-Amz-Date: 20160506T182145Z 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 { "PolicyName": "myscalablepolicy", "ServiceNamespace": "elasticache", "ResourceId": "replication-group/myscalablecluster", "ScalableDimension": "elasticache:replication-group:Replicas" } ``` # Use CloudFormation for Auto Scaling policies This snippet shows how to create a scheduled action and apply it to an [AWS::ElastiCache::ReplicationGroup](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticache-replicationgroup.html) resource using the [AWS::ApplicationAutoScaling::ScalableTarget](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-applicationautoscaling-scalabletarget.html) resource. It uses the [Fn::Join](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-join.html) and [Ref](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-ref.html) intrinsic functions to construct the `ResourceId` property with the logical name of the `AWS::ElastiCache::ReplicationGroup` resource that is specified in the same template. ``` ScalingTarget: Type: 'AWS::ApplicationAutoScaling::ScalableTarget' Properties: MaxCapacity: 0 MinCapacity: 0 ResourceId: !Sub replication-group/${logicalName} ScalableDimension: 'elasticache:replication-group:Replicas' ServiceNamespace: elasticache RoleARN: !Sub "arn:aws:iam::${AWS::AccountId}:role/aws-service-role/elasticache.application-autoscaling.amazonaws.com/AWSServiceRoleForApplicationAutoScaling_ElastiCacheRG" ScalingPolicy: Type: "AWS::ApplicationAutoScaling::ScalingPolicy" Properties: ScalingTargetId: !Ref ScalingTarget ServiceNamespace: elasticache PolicyName: testpolicy PolicyType: TargetTrackingScaling ScalableDimension: 'elasticache:replication-group:Replicas' TargetTrackingScalingPolicyConfiguration: PredefinedMetricSpecification: PredefinedMetricType: ElastiCacheReplicaEngineCPUUtilization TargetValue: 40 ``` # Scheduled scaling Scaling based on a schedule enables you to scale your application in response to predictable changes in demand. To use scheduled scaling, you create scheduled actions, which tell ElastiCache for Valkey and Redis OSS to perform scaling activities at specific times. When you create a scheduled action, you specify an existing ElastiCache cluster, when the scaling activity should occur, minimum capacity, and maximum capacity. You can create scheduled actions that scale one time only or that scale on a recurring schedule. You can only create a scheduled action for ElastiCache clusters that already exist. You can't create a scheduled action at the same time that you create a cluster. For more information on terminology for scheduled action creation, management, and deletion, see [ Commonly used commands for scheduled action creation, management, and deletion ](https://docs.aws.amazon.com/autoscaling/application/userguide/application-auto-scaling-scheduled-scaling.html#scheduled-scaling-commonly-used-commands) **To create a one-time scheduled action:** Similar to Shard dimension. See [Scheduled scaling](AutoScaling-with-Scheduled-Scaling-Shards.md). **To delete a scheduled action** Similar to Shard dimension. See [Scheduled scaling](AutoScaling-with-Scheduled-Scaling-Shards.md). **To manage scheduled scaling using the AWS CLI ** Use the following application-autoscaling APIs: + [put-scheduled-action](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/put-scheduled-action.html) + [describe-scheduled-actions](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/describe-scheduled-actions.html) + [delete-scheduled-action](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/delete-scheduled-action.html) ## Use CloudFormation to create Auto Scaling policies This snippet shows how to create a scheduled action and apply it to an [AWS::ElastiCache::ReplicationGroup](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticache-replicationgroup.html) resource using the [AWS::ApplicationAutoScaling::ScalableTarget](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-applicationautoscaling-scalabletarget.html) resource. It uses the [Fn::Join](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-join.html) and [Ref](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-ref.html) intrinsic functions to construct the `ResourceId` property with the logical name of the `AWS::ElastiCache::ReplicationGroup` resource that is specified in the same template. ``` ScalingTarget: Type: 'AWS::ApplicationAutoScaling::ScalableTarget' Properties: MaxCapacity: 0 MinCapacity: 0 ResourceId: !Sub replication-group/${logicalName} ScalableDimension: 'elasticache:replication-group:Replicas' ServiceNamespace: elasticache RoleARN: !Sub "arn:aws:iam::${AWS::AccountId}:role/aws-service-role/elasticache.application-autoscaling.amazonaws.com/AWSServiceRoleForApplicationAutoScaling_ElastiCacheRG" ScheduledActions: - EndTime: '2020-12-31T12:00:00.000Z' ScalableTargetAction: MaxCapacity: '5' MinCapacity: '2' ScheduledActionName: First Schedule: 'cron(0 18 * * ? *)' ```