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.
When you invoke a function (AWS::Lambda::Function or AWS::Serverless::Function) that uses Layers, SAM CLI downloads the layer and makes it available in the container for your function code to use.
fix: AWS CLI on windows can be called aws.cmd or aws.exe (#786)
fix: typo in development guide doc (#791)
fix: astroid version (#795)
fix: Allow local paths for AWS::Lambda::Function (#808)
chore: Update aws-lambda-builders (#808)
feat: Support Python3.7, Ruby2.5, and Provided Runtimes (#808)
feat: Support local testing and debugging of functions that use Layers (#808)