ScalingPolicy

Source: src/AWS/ApplicationAutoScaling/ScalingPolicy.ts

An Application Auto Scaling scaling policy attached to a scalable target.

Supports TargetTrackingScaling (Application Auto Scaling creates and manages the CloudWatch alarms) and StepScaling (you attach the policy to your own alarm). The policy applies to the scalable target identified by the (serviceNamespace, resourceId, scalableDimension) triple, which must be registered (see ScalableTarget) before the policy is created — pass the target’s outputs so deployment orders correctly.

Target Tracking

Track ECS Service CPU

const target = yield* ScalableTarget("ApiScaling", {
  serviceNamespace: "ecs",
  resourceId: Output.interpolate`service/${cluster.clusterName}/${service.serviceName}`,
  scalableDimension: "ecs:service:DesiredCount",
  minCapacity: 1,
  maxCapacity: 3,
});

yield* ScalingPolicy("ApiCpuPolicy", {
  serviceNamespace: target.serviceNamespace,
  resourceId: target.resourceId,
  scalableDimension: target.scalableDimension,
  targetTracking: {
    TargetValue: 60,
    PredefinedMetricSpecification: {
      PredefinedMetricType: "ECSServiceAverageCPUUtilization",
    },
    ScaleOutCooldown: 60,
    ScaleInCooldown: 60,
  },
});

Track a Customized Metric

yield* ScalingPolicy("QueueDepthPolicy", {
  serviceNamespace: target.serviceNamespace,
  resourceId: target.resourceId,
  scalableDimension: target.scalableDimension,
  targetTracking: {
    TargetValue: 100,
    CustomizedMetricSpecification: {
      MetricName: "ApproximateNumberOfMessagesVisible",
      Namespace: "AWS/SQS",
      Dimensions: [{ Name: "QueueName", Value: "my-queue" }],
      Statistic: "Average",
    },
  },
});

Step Scaling

yield* ScalingPolicy("ApiStepPolicy", {
  serviceNamespace: target.serviceNamespace,
  resourceId: target.resourceId,
  scalableDimension: target.scalableDimension,
  stepScaling: {
    AdjustmentType: "ChangeInCapacity",
    Cooldown: 60,
    MetricAggregationType: "Average",
    StepAdjustments: [
      { MetricIntervalLowerBound: 0, ScalingAdjustment: 1 },
    ],
  },
});