logRetention field is deprecated, logGroup is required

[nsteffens]

Environment information

❯ npx ampx info                                                                                                                                                                                           
System:
  OS: macOS 15.6
  CPU: (12) arm64 Apple M3 Pro
  Memory: 193.63 MB / 36.00 GB
  Shell: /bin/zsh
Binaries:
  Node: 22.14.0 - ~/.nvm/versions/node/v22.14.0/bin/node
  Yarn: undefined - undefined
  npm: 10.9.2 - ~/.nvm/versions/node/v22.14.0/bin/npm
  pnpm: undefined - undefined
NPM Packages:
  @aws-amplify/auth-construct: 1.8.1
  @aws-amplify/backend: 1.16.1
  @aws-amplify/backend-ai: Not Found
  @aws-amplify/backend-auth: 1.7.1
  @aws-amplify/backend-cli: 1.8.0
  @aws-amplify/backend-data: 1.6.1
  @aws-amplify/backend-deployer: 2.1.3
  @aws-amplify/backend-function: 1.14.1
  @aws-amplify/backend-output-schemas: 1.7.0
  @aws-amplify/backend-output-storage: 1.3.1
  @aws-amplify/backend-secret: 1.4.0
  @aws-amplify/backend-storage: 1.4.1
  @aws-amplify/cli-core: 2.2.1
  @aws-amplify/client-config: 1.8.0
  @aws-amplify/data-construct: 1.16.3
  @aws-amplify/data-schema: 1.21.1
  @aws-amplify/deployed-backend-client: 1.8.0
  @aws-amplify/form-generator: 1.2.4
  @aws-amplify/model-generator: 1.2.0
  @aws-amplify/platform-core: 1.10.0
  @aws-amplify/plugin-types: 1.11.0
  @aws-amplify/sandbox: 2.1.2
  @aws-amplify/schema-generator: 1.4.0
  @aws-cdk/toolkit-lib: 1.1.1
  aws-amplify: 6.15.5
  aws-cdk-lib: 2.211.0
  typescript: 5.9.2
AWS environment variables:
  AWS_PROFILE = XXXXXXXXXXXXXXXXX

Describe the bug

I have a very simple lambda function added:

import { defineFunction } from "@aws-amplify/backend";

export const taskDispatcher = defineFunction({
  name: "task-dispatcher",
  entry: "./handler.ts",
  timeoutSeconds: 10,
  logging: {
    retention: "1 month",
  },
});

This compiles fine, still shows this warning for all of my lambdas:

3:58:11 PM [WARNING] aws-cdk-lib.aws_lambda.FunctionOptions#logRetention is deprecated.
3:58:11 PM   use `logGroup` instead
3:58:11 PM   This API will be removed in the next major release.

Furthermore, the whole logging field is not documented. I only found out about this by accident in a PR in this repo..

Reproduction steps

Use the example above. Run it. Warning appears.

[pahud]

Hi @nsteffens,

Thank you for reporting this issue! You've identified two important problems:

1. Deprecation Warning: The warning you're seeing comes from our usage of the deprecated logRetention property in the underlying AWS CDK. We need to update our implementation to use the newer logGroup approach instead of the deprecated logRetention property in the NodejsFunction constructor.

2. Documentation Gap: You're absolutely right that the logging field is undocumented. This feature was implemented as part of support configuring function log settings #2058 but the documentation wasn't updated accordingly.

The fix involves updating the AmplifyFunction constructor to create a LogGroup construct and pass it via the logGroup property instead of using the deprecated logRetention property.

Would you be interested in contributing a PR to fix this? The changes needed are:

1. Update the NodejsFunction instantiation to use logGroup instead of logRetention
2. Add documentation for the logging configuration options
3. Add tests to ensure the LogGroup is created correctly

This is a great opportunity to contribute to the Amplify ecosystem and help other developers avoid this confusion!

Let me know if you'd like guidance on implementing the fix or if you have any questions about the proposed solution.

[nsteffens]

I've just created #2968 to prepare the implementation.