Sharing code in AWS Lambda

Question

What is the prefered way to share code between AWS Lambda functions?

I have a structure like this:

• functions
  • a
    • node_modules
    • index.js
    • package.json
  • b
    • node_modules
    • index.js
    • package.json
  • c
    • node_modules
    • index.js
    • package.json

This lets every function keep its own node_modules and I can package the whole thing with the CLI.

But what about custom code that needs to be shared?

I can require("../mylibrary") but the package command would still not include it.

Answer 1

It is possible with Lambda Layers. Follow this sample SAM template code:

Globals:

  Function:

    Runtime: nodejs8.10

MyFunction:

    Type: AWS::Serverless::Function

    Properties:

        CodeUri: a/

        Handler: index.handler

        Layers:

        - !Ref MySharedLayer

MySharedLayer:

    Type: AWS::Serverless::LayerVersion

    Properties:

        LayerName: SharedLayer

        Description: sharing code is good

        ContentUri: layer/

        CompatibleRuntimes:

            - nodejs8.10

        RetentionPolicy: Retain