1.1.0 • Public • Published


This module will allow you to use json files to decorate your serverless code. Those json files will be used to generate out a valid SAM Template.

tldr; Check out the simple example here

Place your function.json description file next to your code so it makes it simple to add a new function to your API Gateway and no more cutting and pasting large chunks of YAML in your sam template.

Here is an example of a Web Socket API Gateway route handler.

  "functionName": "GetUserFunction",
  "routeKey": "get-user",
  "apiId": "ApiBuiltBySamHelper",
  "handler": "user/index.getHandler",
  "codeUri": "./",
  "policies": ["AmazonAPIGatewayInvokeFullAccess", "AmazonAPIGatewayAdministrator"]

That little description will generate out all of this YAML for you:

  # Route 
  #  Key: get-user route handler 
  #  Handler: GetUserFunction 
    Type: AWS::ApiGatewayV2::Route
      ApiId: !Ref ApiBuiltBySamHelper
      RouteKey: get-user
      AuthorizationType: NONE
      OperationName: GetUserFunctionRoute
      Target: !Join
        - '/'
        - - 'integrations'
          - !Ref GetUserFunctionInteg
    Type: AWS::ApiGatewayV2::Integration
      ApiId: !Ref ApiBuiltBySamHelper
      Description: GetUserFunction Integration
      IntegrationType: AWS_PROXY
          arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${ GetUserFunction.Arn }/invocations
    Type: AWS::Lambda::Permission
      - ApiBuiltBySamHelper
      - GetUserFunction
      Action: lambda:InvokeFunction
      FunctionName: !Ref GetUserFunction
    Type: AWS::Serverless::Function
      Handler: user/index.getHandler
      Timeout: 30
      Runtime: nodejs8.10
      CodeUri: ./
        - AmazonAPIGatewayInvokeFullAccess
        - AmazonAPIGatewayAdministrator

You can also define the API Gateway API in your package.json file with this simple little addition:

      "apiId": "ApiBuiltBySamHelper",
      "apiName": "my-api-from-sam",
      "stageName": "v1",
      "stageDescription": "Version 1 of the api.",
      "routeSelectionExpression": "$request.body.action",
      "type": "websocket"

The function.json and addition to the package.json file generates 82 lines of syntatcitcally correct SAM Template YaML.

Watch the video below to see the helper in action.



Install the helper into your serverless application.

yarn add aws-websocket-sam-helper

Optionally, you may want to add to your package.json a scripts entry that lets you run the helper.

    "generate-sam-template": "sam-helper"

This will allow you to regenerate your template.yaml file with the command:

yarn generate-sam-template


You need to describe your API Gateway and your Functions. Everything else will be handled for you.

Describe API Gateway

Add an api key to your package.json file to describe your API Gateway(s).

      "apiId": "ApiBuiltBySamHelper",
      "apiName": "my-api-from-sam",
      "stageName": "v1",
      "stageDescription": "Version 1 of the api.",
      "routeSelectionExpression": "$request.body.action",
      "type": "websocket"
property description
apiId This is the identifier for this API Gateway. When describing a Function you will refer to this ID. This ID is only used when creating relationships in your template.yaml file.
apiName This name will display in your AWS API Gateway Console. You must name the API so that it meeds the api name constraints.
stageName When deploying, what is the name of the stage. This is the start of your API Gateway URL.
stageDescription Describe the stage.
routeSelectionExpression See the API Gateway documentation for this. This expression describes where in the WebSocket message to look for a value which will contain your route key.
type websocket or rest, currently only websocket is supported at this time.

Describe a Function

Anywhere in your project folder structure you can define function.json files (or *.function.json). The contents of this file describe your Lambda function and relate it to an API Gateway Route or Endpoint.

  "functionName": "GetUserFunction",
  "routeKey": "get-user",
  "apiId": "ApiBuiltBySamHelper",
  "handler": "user/index.getHandler",
  "codeUri": "./",
  "policies": ["AmazonAPIGatewayInvokeFullAccess", "AmazonAPIGatewayAdministrator"]

For example, if you have a sub folder in your project named user and you have an index.js file that defines your Lambda with an export named getHandler the above json file will hook it up to your API Gateway named ApiBuildBySamHelper.

property description default required
functionName A YAML compatible function name. This is used in the SAM Template to refer to your function. It is suggested to use a Proper or Camel case syntax of just upper and lower case letters. yes
routeKey For a web socket route handler this is the key that will route a message to this lambda. yes (for websocket)
apiId The api id you configured in your package.json to identify the api gateway. This connects this function to the APIGW yes
handler This is the location of the exported lambda function. Note the format is {relative_file_path}/{javascript_file_name}.{exported_function_name} index.handler no
codeUri Defined the root of the deployed lambda code. ./ no
policies Any AWS Policies you want defined on your lambda. no
timeout Max time in seconds that your Lambda can stay alive. 30 no
runtime Any valid Lambda Runtime value. nodejs8.10 no
environmentVariables An object representing key value pairs of Environment Variables you wish to add to the Lambda. ex: { name: 'NODE_ENV', value: 'dev' } no

Command Line Arguments

The way you use sam-helper is customizable. Executing sam-helper with no arguments uses a sane set of default values which should cover most situations. However, for the more advanced users you can also do things like use your own handlebars formatted YaML snippets to compose your template.yaml or output the rendered yaml to a file of your choosing.

argument description
-V Version. Display the version of the sam-helper.
-t or --template-path The directory containing your custom template files.
--no-write-file Only output the rendered template to the console.
--output-filename The name of the file to write the rendered template to. Default value is template.yaml
--starting-path The starting path to search for *function.json files in your project. Default value is . (your project root)
--api-definition-file A file that contains your api definitions. If not specified, your package.json is inspected for an api property and tht is used.


Use your own template files:

sam-helper --template-path ./my-templates

Only write output to console:

sam-helper --no-write-file

Start looking for source code in a sub directory on your project:

sam-helper --starting-path ./src/lambdas

NOTE: by default the cli will search all folders in your project root and every sub directory included in them. Skipping node_modules




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  • dsandor