feat(ecs-patterns): enable Backlog per instance scaling in QueueProcessingFargateService

[Abdul-pitodia]

Issue #34072

Closes #34072.

Reason for this change

AWS Documentation recommends a Backlog per instance scaling strategy for Queue based workloads Scale SQS queue using custom metric

Currently QueueProcessingFargateService does not natively support this type of target tracking scaling strategy. The only options currently are to depend on CPU Based Scaling or scaling based on SQS metric called ApproximateNumberOfMessagesVisible.

This PR aims to add the necessary scaling strategy to QueueProcessingFargateService which will allow the service to scale based on the backlog per instance.

Note: ContainerInsights must be enabled on the cluster to publish the metric RunningTaskCount

Description of changes

• Added support for using MathExpression in TargetTrackingScalingPolicy under aws-applicationauatoscaling
• Added enableBacklogPerInstanceBasedScaling and backlogPerInstanceTargetValue properties for enabling and defining the Backlog scaling
• Updated configureAutoscalingForService method to work with the above properties to enable the scaling strategy in QueueProcessingServiceBase. Used Official documentation for scaling strategy implementation

Describe any new or updated permissions being added

N/A – no new permissions are introduced in this change.

Description of how you validated changes

• Added unit test for testing Target tracking using Math Expression Construct in packages/aws-cdk-lib/aws-applicationautoscaling/test/target-tracking.test.ts
• Added unit test for testing Backlog per instance scaling in packages/aws-cdk-lib/aws-ecs-patterns/test/fargate/queue-processing-fargate-service.test.ts
• Added new integration test packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/fargate/integ.queue-processing-fargate-service-backlog-per-instance-scaling.ts
• Tested by deploying the integration test App, attached images.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

(This review is outdated)

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[Abdul-pitodia]

I was getting a error from the Code build job complaining about the version mismatch in the manifest.json

I have followed the integration test guideline to generate the snapshot, which outputted the version to 43.0.0

@aws-cdk-testing/framework-integ:   ERROR      aws-ecs-patterns/test/fargate/integ.queue-processing-fargate-service-backlog-per-instance-scaling 0.804s
@aws-cdk-testing/framework-integ:       Cannot read integ manifest 'test/aws-ecs-patterns/test/fargate/integ.queue-processing-fargate-service-backlog-per-instance-scaling.js.snapshot/manifest.json': Cloud assembly schema version mismatch: Maximum schema version supported is 42.x.x, but found 43.0.0. You need at least CLI version 2.1008.0 to read this manifest.

I have updated the version manually to 42.0.0 in the manifest.json in this commit

Please let me know if its fine, or any other way to fix this issue

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: e5bd600
• Result: SUCCEEDED
• Build Logs (available for 30 days)

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