ecsfs_auto_scaling.yaml

# Specifies a resource that Application Auto Scaling can scale. In our case
# it's just the backend.
AutoScalingTarget:
  Type: AWS::ApplicationAutoScaling::ScalableTarget
  Properties:
    MinCapacity: 1
    MaxCapacity: 3
    ResourceId: !Join ['/', [service, !Ref ECSCluster, !GetAtt BackendService.Name]]
    ScalableDimension: ecs:service:DesiredCount
    ServiceNamespace: ecs
    RoleARN: !GetAtt AutoScalingRole.Arn

# Describes the rules for ECS to check and decide when it should scale up or
# down a service. In our application we just scale the backend.
AutoScalingPolicy:
  Type: AWS::ApplicationAutoScaling::ScalingPolicy
  Properties:
    PolicyName: BackendAutoScalingPolicy
    PolicyType: TargetTrackingScaling
    ScalingTargetId: !Ref AutoScalingTarget
    TargetTrackingScalingPolicyConfiguration:
      PredefinedMetricSpecification:
        PredefinedMetricType: ECSServiceAverageCPUUtilization
      ScaleInCooldown: 10
      ScaleOutCooldown: 10
      TargetValue: 50