aws-lambda: Simplify Lambda provisioned concurrency autoscaling

[pahud]

Provisioned concurrency for Lambda function is a huge announcement last year in re:Invent and the Lambda developer guide has a chapter talking about how to configure provisioned concurrency auto scaling with target tracking with AWS CLI like this:

$ aws lambda put-provisioned-concurrency-config --function-name my-function \
--qualifier BLUE --provisioned-concurrent-executions 100
{
    "Requested ProvisionedConcurrentExecutions": 100,
    "Allocated ProvisionedConcurrentExecutions": 0,
    "Status": "IN_PROGRESS",
    "LastModified": "2019-11-21T19:32:12+0000"
}

$ aws application-autoscaling register-scalable-target --service-namespace lambda \
      --resource-id function:my-function:BLUE --min-capacity 1 --max-capacity 100 \
      --scalable-dimension lambda:function:ProvisionedConcurrency

$ aws application-autoscaling put-scaling-policy --service-namespace lambda \
--scalable-dimension lambda:function:ProvisionedConcurrency --resource-id function:my-function:BLUE \
--policy-name my-policy --policy-type TargetTrackingScaling \
--target-tracking-scaling-policy-configuration '{ "TargetValue": 0.7, "PredefinedMetricSpecification": { "PredefinedMetricType": "LambdaProvisionedConcurrencyUtilization" }}'
{
    "PolicyARN": "arn:aws:autoscaling:us-east-2:123456789012:scalingPolicy:12266dbb-1524-xmpl-a64e-9a0a34b996fa:resource/lambda/function:my-function:BLUE:policyName/my-policy",
    "Alarms": [
        {
            "AlarmName": "TargetTracking-function:my-function:BLUE-AlarmHigh-aed0e274-xmpl-40fe-8cba-2e78f000c0a7",
            "AlarmARN": "arn:aws:cloudwatch:us-east-2:123456789012:alarm:TargetTracking-function:my-function:BLUE-AlarmHigh-aed0e274-xmpl-40fe-8cba-2e78f000c0a7"
        },
        {
            "AlarmName": "TargetTracking-function:my-function:BLUE-AlarmLow-7e1a928e-xmpl-4d2b-8c01-782321bc6f66",
            "AlarmARN": "arn:aws:cloudwatch:us-east-2:123456789012:alarm:TargetTracking-function:my-function:BLUE-AlarmLow-7e1a928e-xmpl-4d2b-8c01-782321bc6f66"
        }
    ]
}

In the latest aws-cdk v1.25.0 we start supporting aws-applicationautoscaling with Lambda(PR) and I have yet another PR(#6394 ) to make it complete. We should be able to build the provisioned concurrency autoscaling like this

To make it even simplied, as the provisioned concurrency can be configured over any lambda function version or alias, we probably can extend the lambda.Version class by adding a scaleOnProvisionedConcurrency function like this

  public scaleOnProvisionedConcurrency(props: ScaleProvisionedConcurrencyProps): applicationautoscaling.TargetTrackingScalingPolicy {
      return new applicationautoscaling.ScalableTarget(this, 'ScalableLambdaTarget', {
      serviceNamespace: applicationautoscaling.ServiceNamespace.LAMBDA,
      maxCapacity: props.max,
      minCapacity: props.min,
      resourceId: `function:${this.functionName}:${this.version}`,
      scalableDimension: 'lambda:function:ProvisionConcurrency',
    })
      .scaleToTrackMetric('PceTracking', {
        targetValue: props.target,
        predefinedMetric: applicationautoscaling.PredefinedMetric.LAMBDA_PROVISIONED_CONCURRENCY_UTILIZATION,
      });
  }

And in this case, all lambda function alias can have autoscaling capabilities. Sample code here

Any thoughts?

Use Case

To make any AWS Lambda function version or alias very easy to enable its provisioned concurrency auto scaling capabilities.

Proposed Solution

described above

Other

• [v] 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

---

This is a 🚀 Feature Request

[nija-at]

Thanks for filing this issue. In general, we should have this feature included into the CDK.

There's a few things we should consider during the start of implementation -

• be careful about how we connect this to versions. We have a reported bug that causes versions to not update as expected - Deploying new version of lambda function #5334. It might turn out that we have to fix up this behaviour before implementing this feature.
• work out what the right location for this package would be. There are two options, either in the @aws-cdk/aws-lambda package or a new @aws-cdk/aws-autoscaling-targets package.

Finally, the API signatures you've suggested need to be tuned for a more ergonomic customer experience.

[eladb]

Related: #6771