ECS Cluster ASG drain hook uses deprecated Python 3.9 runtime

[naqqash-khan-audi]

The ECS Cluster Auto Scaling Group (ASG) drain hook defined in instance-drain-hook.ts currently uses the Python 3.9 runtime.

https://github.com/aws/aws-cdk/blob/v1-main/packages/%40aws-cdk/aws-ecs/lib/drain-hook/instance-drain-hook.ts#L70

However, AWS has announced that Python 3.9 will soon be deprecated and no longer supported in Lambda. To ensure future compatibility and avoid potential disruptions, this runtime should be updated to a supported version.

Thank you,
Naqqash Khan

[DYNOSuprovo]

Hi @naqqash-khan-audi!

Here is the situation regarding this Lambda runtime and how to address it immediately in your stacks:

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1. CDK v1 End-of-Life (EOL) Notice

Notice that the GitHub URL referenced in your report points to the v1-main branch:

https://github.com/aws/aws-cdk/blob/v1-main/packages/@aws-cdk/aws-ecs/lib/drain-hook/instance-drain-hook.ts#L70

AWS CDK v1 officially reached End-of-Life on June 1, 2023. Per AWS policy, the CDK team does not backport new Lambda runtimes or maintenance updates to the v1-main repository or the deprecated @aws-cdk/* individual npm packages.

In AWS CDK v2 (aws-cdk-lib), the default Lambda runtime for provider frameworks and internal lifecycle hooks (including the ECS Auto Scaling drain hook) has been updated to active Python runtimes (python3.11 / python3.12).

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2. Immediate Fix via Escape Hatch / Aspect (No CDK Upgrade Needed)

If your team is in the process of upgrading CDK versions and needs to eliminate the deprecated python3.9 runtime warning immediately, you do not need to wait or patch construct internals.

You can use an Aspect to override the underlying AWS::Lambda::Function CloudFormation resource at synthesis time across your entire stack or app:

import * as cdk from 'aws-cdk-lib';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import { IConstruct } from 'constructs';

class UpgradeDrainHookRuntime implements cdk.IAspect {
  visit(node: IConstruct): void {
    if (node instanceof lambda.CfnFunction) {
      if (node.runtime === 'python3.9') {
        node.runtime = 'python3.12'; // or 'python3.11'
      }
    }
  }
}

// Apply to your Stack or App:
cdk.Aspects.of(app).add(new UpgradeDrainHookRuntime());

Because the Python Lambda handler code in the drain hook relies only on standard AWS SDK calls (boto3) and built-in Python standard libraries, it executes seamlessly on python3.11 and python3.12 without any code modifications.

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3. Recommended Path: Upgrade to AWS CDK v2 (aws-cdk-lib)

If your project is still using CDK v1 (@aws-cdk/aws-ecs, @aws-cdk/core, etc.):

1. Update your dependencies to aws-cdk-lib (v2.x).
2. Replace all scoped @aws-cdk/* imports with:

   import { Stack, App, Duration } from 'aws-cdk-lib';
   import * as ecs from 'aws-cdk-lib/aws-ecs';
   import * as autoscaling from 'aws-cdk-lib/aws-autoscaling';

3. CDK v2 is actively maintained and receives automatic runtime updates as AWS Lambda deprecation schedules advance.

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If this helps clarify the branch deprecation and provides a working override for your deployment, please feel free to mark this as the accepted answer!