(aws-autoscaling/aws-applicationautoscaling): StepScalingPolicy supports at most 40 steps #26215
Description
Describe the bug
If you create a StepScalingPolicy with more than 40 steps, the Cloudformation deployment fails with the message "There can be at most 20 step adjustments per scaling policy".
The reason the limit is 40 and not 20 is because StepScalingPolicy creates two policies, an UpperPolicy and a LowerPolicy, each containing half the steps.
Expected Behavior
The deployment succeeds, with the steps split across the required number of policies.
If I've misunderstood the code, and there's a reason to specifically have two policies, I'd expect a build time failure from CDK when the number of steps exceeds 40, rather than a build time failure.
Current Behavior
Cloudformation deployment fails with the message "There can be at most 20 step adjustments per scaling policy".
Reproduction Steps
Starting with a Fargate Service and an SQS queue (I'm trying to reproduce the tracking policy https://docs.aws.amazon.com/autoscaling/ec2/userguide/ec2-auto-scaling-target-tracking-metric-math.html describes without using metric math).
maximum_number_of_tasks = 50
desired_messages_per_task = 20
scaling = service.auto_scale_task_count(
min_capacity=1,
max_capacity=maximum_number_of_tasks,
)
scaling_steps = [
aws_applicationautoscaling.ScalingInterval(
lower=step_number * desired_messages_per_task,
upper=step_number * (desired_messages_per_task + 1) - 1,
change=step_number + 1,
)
for step_number
in range(0, maximum_number_of_tasks)
]
scaling.scale_on_metric(
id="Track visible messages per task",
metric=queue.metric_approximate_number_of_messages_visible(
statistic="Average",
period=Duration.minutes(1),
),
adjustment_type=aws_autoscaling.AdjustmentType.EXACT_CAPACITY,
scaling_steps=scaling_steps,
cooldown=Duration.minutes(3),
)
Possible Solution
Allow for more than two scaling policies to be created (this may not make sense, my understanding of these policies is not great).
Additional Information/Context
No response
CDK CLI Version
2.86.0 (build 1130fab)
Framework Version
2.81.0
Node.js Version
v16.18.1
OS
Ubuntu (Windows Subsystem for Linux)
Language
Python
Language Version
3.9.7
Other information
No response