scaleOnMetric does not allow to change periods/datapoints to alarm

Hi , how to change the defaults alarms created with autoscaling module for scaleOnMetric ? It sets datapoints to 1 and period to 60s. I tried this but it does not work (shows no changes):

scaling = autoscalinggroup.scale_on_metric(
            f'ScaleToNrMessInQueue-{stage}-{app_name}-{version}',
            metric=queue.metric("ApproximateNumberOfMessagesVisible"),
            scaling_steps=[
                autoscaling.ScalingInterval(upper=0, change=0),
                autoscaling.ScalingInterval(lower=0, upper=1, change=1),
                autoscaling.ScalingInterval(lower=2, upper=3, change=2),
                autoscaling.ScalingInterval(lower=3, change=3)
            ],
            adjustment_type=autoscaling.AdjustmentType.EXACT_CAPACITY
        )

scaling.lower_alarm.datapoints_to_alarm = 5
scaling.lower_alarm.evaluation_periods = 5
scaling.lower_alarm.period = core.Duration.minutes(5)

I see one such property hardcoded here https://github.com/aws/aws-cdk/blob/master/packages/@aws-cdk/aws-autoscaling/lib/step-scaling-policy.ts#L110

Environment

• CDK CLI Version: 1.19.0 (build 5597bbe)
• Module Version: latest/master
• OS: Windows 7
• Language: Python

[NetaNir]

@toleabivol,

Wouldn’t you be able to achieve this by setting grace on the health_check property of the autoscalinggroup to allow warm up time? see CloudFormation docs.

You can add it to the autoscalinggroup:

        asg = autoscaling.AutoScalingGroup(
        self,
        "ASG",
        vpc=vpc,
        instance_type=ec2.InstanceType.of(
        ec2.InstanceClass.BURSTABLE2, ec2.InstanceSize.MICRO,
        ),
        health_check=autoscaling.HealthCheck.ec2(grace=core.Duration.seconds(5)),
        machine_image=ec2.AmazonLinuxImage(generation=ec2.AmazonLinuxGeneration.AMAZON_LINUX_2)
        )

Generally, to override the lower_alarm properties you need to use escape hatches which will allow you to override the defined alarm properties:

cfn_alarm = scaling.lower_alarm.node.default_child
cfn_alarm.evaluation_periods = 5

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