AutoScaling: Validate use of Cooldown

[ryanwilliams83]

Describe the feature

Cooldown only applies to simple scaling policy.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-autoscaling-scalingpolicy.html#cfn-autoscaling-scalingpolicy-cooldown

Please consider enhancing CDK to trap for the following configuration when executed with the --ci switch.
To inform users that the cooldown will not have any effect.

asg.ScaleOnCpuUtilization('ALowCpuLoad', {
cooldown = cdk.Duration.minutes(666), // Has no effect when the policyType is TargetTrackingScaling
estimatedInstanceWarmup = cdk.Duration.minutes(10),
targetUtilizationPercent: 45
});

Use Case

I was mislead by the CDK intrinsic documentation.

Cooldown: Period after a scaling completes before another scaling activity can start.
Default: The default cooldown configured on the AutoScalingGroup.

Proposed Solution

No response

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.165.0

Environment details (OS name and version, etc.)

Windows, C#, Constructs 10.4.2

[ryanwilliams83]

An example of some synthesized CloudFormation containing Cooldown and also TargetTrackingScaling.

    "AutoScalingGroupScalingPolicyALowCpuLoadE60B7782": {
      "Type": "AWS::AutoScaling::ScalingPolicy",
      "Properties": {
        "AutoScalingGroupName": {
          "Ref": "AutoScalingGroupASG804C35BE"
        },
        "Cooldown": "1500",
        "EstimatedInstanceWarmup": 1200,
        "PolicyType": "TargetTrackingScaling",
        "TargetTrackingConfiguration": {
          "PredefinedMetricSpecification": {
            "PredefinedMetricType": "ASGAverageCPUUtilization"
          },
          "TargetValue": 45
        }
      },
      "DependsOn": [
        "AutoScalingGroupWarmPool7145D5D8",
        "SsmParameterCloudWatchAgentConfig"
      ],
      "Metadata": {
        "aws:cdk:path": "GisMaps/AutoScalingGroup/ScalingPolicyALowCpuLoad/Resource"
      }
    },

[khushail]

@ryanwilliams83 , thanks for reaching out.

Please help me re-iterate on your ask here -

1. More clear CDK Documentationa around cooldown property here which says -

cooldown?

Type: [Duration](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Duration.html) (optional, default: Duration.minutes(5))

Default scaling cooldown for this AutoScalingGroup.

while in Cloudformation docs, its clearly mentioned that Cooldown is needed only if you use simple scaling policies.

2. Feature request for addition of this --ci which would work for TargetScalingPolicy and coolDown` will have no effect as mentioned in this API Doc as suggested in your code.

[ryanwilliams83]

@khushail, please disregard the --ci switch that I mentioned.
I thought it introduced additional sanity checks during synth but I must be mistaken because the cdk --help documentation simply states.

--ci                 Force CI detection. If CI=true then logs will be sent
                           to stdout instead of stderr[boolean] [default: false]

So to reiterate,

1. Please update the CDK documentation on the cooldown property so it clearly informs users that it only applies to SimpleScalingPolicies.
2. Please consider modifying CloudFormation to warn or reject templates that attempt to specify the Cooldown property in conjunction with a Policy other than simple.

[khushail]

@khushail, please disregard the --ci switch that I mentioned. I thought it introduced additional sanity checks during synth but I must be mistaken because the cdk --help documentation simply states.

--ci                 Force CI detection. If CI=true then logs will be sent
                           to stdout instead of stderr[boolean] [default: false]

So to reiterate,

1. Please update the CDK documentation on the `cooldown` property so it clearly informs users that it only applies to SimpleScalingPolicies.

2. Please consider modifying CloudFormation to warn or reject templates that attempt to specify the `Cooldown` property in conjunction with a Policy other than simple.

Thanks for clarification there @ryanwilliams83 . Regarding your requests -

1. Documentation around cooldown property in CDK would be helpful to have. Contributions from community are welcome in this regards, hence marking it as P3.
2. This check could be implemented by Cloudformation as the PolicyType is coming from L1 construct. You could open an issue with Cloudformation team, on this Cloudformation coverage roadmap and follow the same for updates.

Hope that would be helpful.