SAM v1.9.0: Lambda Layers and Nested Applications

SAM v1.9.0: Lambda Layers and Nested Applications

Nested Transforms and the AWS::Serverless::Application Resource

You can now assemble and deploy new serverless architectures using nested applications supported by AWS SAM and the AWS Serverless Application Repository.

Nested applications enable you to rapidly build highly sophisticated serverless architectures by reusing and composing authored and maintained services using SAM and the Serverless Application Repository. You can deploy serverless architectures as a set of serverless applications and easily share those architectures privately across teams and organizations or publicly with developers in the open-source community. Using nested applications, you can build more powerful applications, easily manage serverless artifacts, avoid duplicated work, and help ensure consistency and best practices across your teams and organizations.

The new AWS::Serverless::Application transforms into a AWS::CloudFormation::Stack (also known as a nested stack) resource by resolving the Location property to an S3 template URL. SAM users can either provide direct links to a nested template or provide an ApplicationId and SemanticVersion pair from the Serverless Application Repository and SAM will retrieve the template and all its resources for you. This allows developers re-use common application building blocks as well as share and consume them via the Serverless Application Repository.

Learn more in the SAM developer documentation or in the AWS::Serverless::Application specification. We have also included a sample application that uses this feature.

Introducing AWS::Serverless::LayerVersion

Lambda functions in a serverless application typically share common dependencies such as SDKs, frameworks, and runtimes. Lambda Layers are a new type of artifact that can contain arbitrary code and data, and may be referenced by multiple functions at the same time. With layers, you can centrally manage common components across multiple functions enabling better code reuse. You can now use AWS SAM and AWS SAM CLI to locally test, deploy and manage serverless applications that leverage Layers. An AWS::Serverless::LayerVersion transforms into an AWS::Lambda::LayerVersion.

Since an AWS::Lambda::LayerVersion resource is immutable, CloudFormation currently automatically creates a new version and deletes the old version of the Lambda Layer after each update. By default, SAM prevents CloudFormation from deleting old versions by appending a 10-digit SHA (based on all resource parameters) to the logical id of the LayerVersion resource and adding a DeletionPolicy: Retain attribute. This means that any update to the Lambda Layer will result in the creation of a new version, and the old version will still be available for use.

Learn more about Lambda Layers in the Lambda Layers documentation, and in the SAM developer documentation.

Other Updates

#670 Added AWS WorkMail hello world lambda function example
#639 Added link to the new AWS SAM Developer documentation
There were also a few documentation fixes and updates.