Lambda Node.js Example With Swagger Specification

index.js

exports.handler = async function (event) {
  // event variables looks like this:
  //  {
  //   "body": "eyJ0ZXN0IjoiYm9keSJ9",
  //   "resource": "/{proxy+}",
  //   "path": "/path/to/resource",
  //   "httpMethod": "POST",
  //   "isBase64Encoded": true,
  //   "queryStringParameters": {
  //     "foo": "bar"
  //   },
  //   "pathParameters": {
  //     "proxy": "/path/to/resource"
  //   },
  //   "stageVariables": {
  //     "baz": "qux"
  //   },
  //   "headers": {
  //     "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
  //     "Accept-Encoding": "gzip, deflate, sdch",
  //     "Accept-Language": "en-US,en;q=0.8",
  //     "Cache-Control": "max-age=0",
  //     "CloudFront-Forwarded-Proto": "https",
  //     "CloudFront-Is-Desktop-Viewer": "true",
  //     "CloudFront-Is-Mobile-Viewer": "false",
  //     "CloudFront-Is-SmartTV-Viewer": "false",
  //     "CloudFront-Is-Tablet-Viewer": "false",
  //     "CloudFront-Viewer-Country": "US",
  //     "Host": "1234567890.execute-api.us-east-1.amazonaws.com",
  //     "Upgrade-Insecure-Requests": "1",
  //     "User-Agent": "Custom User Agent String",
  //     "Via": "1.1 08f323deadbeefa7af34d5feb414ce27.cloudfront.net (CloudFront)",
  //     "X-Amz-Cf-Id": "cDehVQoZnx43VYQb9j2-nvCh-9z396Uhbp027Y2JvkCPNLmGJHqlaA==",
  //     "X-Forwarded-For": "127.0.0.1, 127.0.0.2",
  //     "X-Forwarded-Port": "443",
  //     "X-Forwarded-Proto": "https"
  //   },
  //   "requestContext": {
  //     "accountId": "123456789012",
  //     "resourceId": "123456",
  //     "stage": "prod",
  //     "requestId": "c6af9ac6-7b61-11e6-9a41-93e8deadbeef",
  //     "requestTime": "09/Apr/2015:12:34:56 +0000",
  //     "requestTimeEpoch": 1428582896000,
  //     "identity": {
  //       "cognitoIdentityPoolId": null,
  //       "accountId": null,
  //       "cognitoIdentityId": null,
  //       "caller": null,
  //       "accessKey": null,
  //       "sourceIp": "127.0.0.1",
  //       "cognitoAuthenticationType": null,
  //       "cognitoAuthenticationProvider": null,
  //       "userArn": null,
  //       "userAgent": "Custom User Agent String",
  //       "user": null
  //     },
  //     "path": "/prod/path/to/resource",
  //     "resourcePath": "/{proxy+}",
  //     "httpMethod": "POST",
  //     "apiId": "1234567890",
  //     "protocol": "HTTP/1.1"
  //   }
  // }

  // Function must return an object like this
  // If API responds with a JSON, headers prop is optional
  return {
    statusCode: 200, // int - HTTP Status Code
    body: JSON.stringify({ myProperty: "myValue" }), // string - Response Body
    headers: {
      'Content-Type': 'application/json'
    }
  };
}

template.yml

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::Serverless-2016-10-31

Resources:
  MyLambda:
    Type: AWS::Serverless::Function
    Properties:
      Handler: index.handler
      CodeUri: .
      Runtime: nodejs8.10
      Environment:
        Variables:
          VARIABLE: value
          # Add any external param here, such as endpoints, references to other resources etc.
          # that this function should be aware of.
      Events:
        Api:
          Type: Api
          Properties:
            Method: get
            Path: /mypath
            RestApiId: !Ref MyRestApi

  MyRestApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: v1
      DefinitionBody:
        openapi: '3.0.1'
        info:
          version: 1.0.0
          title: ContactOne
        paths:
          /mypath:
            get:
              summary: My GET endpoint
              parameters:
                - in: query
                  name: id
                  description: Some ID
                  schema:
                    type: string
              responses:
                "200":
                  $ref: '#/components/responses/default'
              x-amazon-apigateway-integration:
                httpMethod: POST
                type: aws_proxy
                uri: !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${MyLambda.Arn}/invocations
              security:
                - apiKey: []

        components:
          responses:
            default:
              description: OK
              content:
                application/json:
                  schema:
                    $ref: "#/components/schemas/MySchema"
          schemas:
            MySchema:
              type: object
              properties:
                myProperty:
                  type: string
          securitySchemes:
            apiKey:
              type: apiKey
              name: x-api-key
              in: header