AWS::Serverless Transform - AWS CloudFormation

AWS::Serverless Transform

The AWS::Serverless transform, which is a macro hosted by AWS CloudFormation, takes an entire template written in the AWS Serverless Application Model (AWS SAM) syntax and transforms and expands it into a compliant AWS CloudFormation template. For more information about serverless applications and AWS SAM, see Deploying Lambda-based Applications in the AWS Lambda Developer Guide.

Unlike custom macros, the AWS::Serverless transform doesn't require any special permissions to use it because it is hosted by AWS CloudFormation. It can be used by templates in any account within AWS CloudFormation. Also, there is no charge incurred when using this transform. AWS CloudFormation treats the AWS::Serverless transform the same as any other macro in terms of evaluation order and scope. For more information about macros, see Using AWS CloudFormation Macros to Perform Custom Processing on Templates.

In the following example, the template uses AWS SAM syntax to simplify the declaration of a Lambda function and its execution role.

Transform: AWS::Serverless-2016-10-31 Resources: MyServerlessFunctionLogicalID: Type: AWS::Serverless::Function Properties: Handler: index.handler Runtime: nodejs8.10 CodeUri: 's3://testBucket/'

When creating a change set from the template, AWS CloudFormation expands the AWS SAM syntax, as defined by the transform. The processed template expands the AWS::Serverless::Function resource, declaring an AWS Lambda function and an execution role.

{ "Resources": { "MyServerlessFunctionLogicalID": { "Type": "AWS::Lambda::Function", "Properties": { "Handler": "index.handler", "Code": { "S3Bucket": "testBucket", "S3Key": "" }, "Role": { "Fn::GetAtt": ["FunctionNameRole", "Arn"] }, "Runtime": "nodejs8.10" } }, "FunctionNameRole": { "Type": "AWS::IAM::Role", "Properties": { "ManagedPolicyArns": ["arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"], "AssumeRolePolicyDocument": { "Version": "2012-10-17", "Statement": [{ "Action": ["sts:AssumeRole"], "Effect": "Allow", "Principal": { "Service": [""] } }] } } } } }


The value for the transform declaration must be a literal string. You cannot use a parameter or function to specify a transform value. The following snippet is an example of a transform declaration:


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


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