CloudFormation Hello World Example

cloudformation_hello_world_1.yaml

AWSTemplateFormatVersion: 2010-09-09

Resources:
  HelloLambdaRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: HelloLambdaRole
      AssumeRolePolicyDocument:
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
                

  HelloLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: HelloLambdaFunction
      Role: !GetAtt HelloLambdaRole.Arn
      Runtime: nodejs14.x
      Handler: index.handler
      Code:
        ZipFile: |
          exports.handler = async (event) => {
            const response = {
              statusCode: 200,
              body: JSON.stringify('Hello from Lambda!'),
            };
            return response;
          };

cloudformation_hello_world_2.yaml

AWSTemplateFormatVersion: 2010-09-09

Resources:
  HelloLambdaRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: HelloLambdaRole
      AssumeRolePolicyDocument:
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole                

  HelloLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: HelloLambdaFunction
      Role: !GetAtt HelloLambdaRole.Arn
      Runtime: nodejs14.x
      Handler: index.handler
      Code:
        ZipFile: |
          exports.handler = async (event) => {
            const response = {
              statusCode: 200,
              body: JSON.stringify('Hello from Lambda!'),
            };
            return response;
          };

  HttpApi:
    Type: AWS::ApiGatewayV2::Api
    Properties:
      Name: HelloWorldApi
      ProtocolType: HTTP
      Target: !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:${HelloLambdaFunction}/invocations
  
  LambdaPermission:
    Type: "AWS::Lambda::Permission"
    Properties:
      Action: lambda:InvokeFunction
      FunctionName: !GetAtt HelloLambdaFunction.Arn
      Principal: apigateway.amazonaws.com
      SourceArn: !Sub 'arn:${AWS::Partition}:execute-api:${AWS::Region}:${AWS::AccountId}:${HttpApi}/*/$default'

Outputs:
  ApiEndpoint:
    Value: !Sub ${HttpApi.ApiEndpoint}