Bug: Lambda function (with alias) doesn't create a new version after its layer is updated, even if AutoPublishAliasAllProperties is set to true

[paulhcsun]

Discussed in #3612

^{Originally posted by zhanzhenzhen May 31, 2024}

Description:

If we use alias for a lambda function (for provisioned concurrency, etc), it won't create a new version after its layer is updated, even if AutoPublishAliasAllProperties is set to true. So the alias still points to the old layer version. But the $LATEST version is synced with the new layer version. Am I missing something, or is it a bug?

Steps to reproduce:

1. Create those 4 files, then sam build, then sam deploy. Visit the output URL.
2. After initial deployment, replace the string "old layer" with "new layer" in the layer/layer.mjs file. Build and deploy it again. Visit the output URL.

template.yaml:

AWSTemplateFormatVersion: "2010-09-09"

Transform:
  - AWS::Serverless-2016-10-31

Globals:
  Api:
    Cors:
      AllowMethods: "'*'"
      AllowHeaders: "'*'"
      AllowOrigin: "'*'"
  Function:
    Runtime: nodejs20.x
    Architectures:
      - arm64
    MemorySize: 128
    Timeout: 8

Resources:
  Layer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      LayerName: !Sub ${AWS::StackName}-Layer
      CompatibleArchitectures:
        - arm64
      CompatibleRuntimes:
        - nodejs20.x
      ContentUri: layer
      RetentionPolicy: Delete
    Metadata:
      BuildMethod: nodejs20.x
      BuildArchitecture: arm64

  AppFunction:
    Type: AWS::Serverless::Function
    Properties:
      AutoPublishAlias: Main
      AutoPublishAliasAllProperties: true
      CodeUri: lambda
      Handler: app.handler
      Layers:
        - !Ref Layer
      Events:
        Api:
          Type: Api
          Properties:
            Path: /app
            Method: GET

Outputs:
  URL:
    Description: "Test URL"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/app"

lambda/app.mjs:

import layer from "/opt/nodejs/layer.mjs";

export const handler = async (event, context) => {
    const response = {
        statusCode: 200,
        body: JSON.stringify({fnVersion: process.env.AWS_LAMBDA_FUNCTION_VERSION, layer: layer})
    };
    return response;
};

layer/layer.mjs:

export default "old layer";

samconfig.toml:

version = 0.1

[default]
[default.global.parameters]
stack_name = "TestApp"

[default.build.parameters]
cached = true
parallel = true

[default.validate.parameters]
lint = true

[default.deploy.parameters]
capabilities = "CAPABILITY_NAMED_IAM"
confirm_changeset = true
resolve_s3 = true
s3_prefix = "TestApp"
image_repositories = []

[default.package.parameters]
resolve_s3 = true

[default.sync.parameters]
watch = true

[default.local_start_api.parameters]
warm_containers = "EAGER"

[default.local_start_lambda.parameters]
warm_containers = "EAGER"

Observed result:

In step 1, the result is: {"fnVersion":"1","layer":"old layer"}.

In step 2, the result remains the same.

Expected result:

I expect the result in step 2 to be {"fnVersion":"2","layer":"new layer"}.

Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: Linux-6.1.90-99.173.amzn2023.x86_64-x86_64-with-glibc2.34
2. sam --version: 1.114.0
3. AWS region: us-east-1