Attach Lambda Layer CloudFormation Custom Resource (CFNAttachLambdaLayer)

Purpose

AWS CloudFormation does not support referencing "the latest version" of a layer when creating a Lambda function. This becomes problematic when the layer was created outside of your CloudFormation template.

CFNAttachLambdaLayer allows you to specify a Lambda and the Layer name that will be attached to it. It will attach the latest version of the Layer to the specified Lambda.

Requirements

• The AWS CLI
• The AWS Serverless Application Model must be installed
• Docker Desktop

Deploying CFNAttachLambdaLayer

From the command line, run:

sam build  --use-container
sam deploy  --stack-name cfn-attach-lambda-layer  --capabilities "CAPABILITY_NAMED_IAM" --resolve-s3 

This will deploy an AWS Lambda custom resource that can be called by your CloudFormation template.

Usage

Parameters:
  Nonce:
    Type: String
    Description: Forces custom resource to run everytime CF runs -- pass in a $RANDOM as a parameter

  AttachLayer:
    Type: Custom::LayerAttachment
    Properties:
      LayerName: <Your Layer name>
      LambdaName: <Lambda name or ARN>
      #CloudFormation will not execute the custom resource if no properties are changed.
      #Along with the parameter, this ensures that the resource is called each time CloudFormation runs
      #If using sam deploy, you can specify:
      #  --parameter-overrides Nonce="$(date +%s)" 
      Nonce: !Ref Nonce
      ServiceToken: !ImportValue CFNAttachLambdaLayer