README.md

cloudformation-step-function-buddy

Write your Step Function definition in JavaScript (instead of JSON) and validate it

Usage

You'll need to be using tool that generates CloudFormation templates from JavaScript. At Mapbox, we use cloudfriend, but any JavaScript-based tool will do.

const cf = require('@mapbox/cloudfriend');
const {
  stringifyDefinition
} = require('@mapbox/cloudformation-step-function-buddy');

module.exports = {
  AWSTemplateFormatVersion: '2010-09-09',
  Description:
    'An example template with an IAM role for a Lambda state machine.',
  Resources: {
    LambdaExecutionRole: {
      Type: 'AWS::IAM::Role',
      Properties: {
        AssumeRolePolicyDocument: {
          Version: '2012-10-17',
          Statement: [
            {
              Effect: 'Allow',
              Principal: {
                Service: 'lambda.amazonaws.com'
              },
              Action: 'sts:AssumeRole'
            }
          ]
        }
      }
    },
    MyLambdaFunction: {
      Type: 'AWS::Lambda::Function',
      Properties: {
        Handler: 'index.handler',
        Role: cf.getAtt('LambdaExecutionRole', 'Arn'),
        Code: {
          ZipFile:
            'exports.handler = (event, context, callback) => { callback(null, "Hello World!");};'
        },
        Runtime: 'nodejs4.3',
        Timeout: '25'
      }
    },
    StatesExecutionRole: {
      Type: 'AWS::IAM::Role',
      Properties: {
        AssumeRolePolicyDocument: {
          Version: '2012-10-17',
          Statement: [
            {
              Effect: 'Allow',
              Principal: {
                Service: cf.sub('states.${AWS::Region}.amazonaws.com')
              },
              Action: 'sts:AssumeRole'
            }
          ]
        },
        Path: '/',
        Policies: [
          {
            PolicyName: 'StatesExecutionPolicy',
            PolicyDocument: {
              Version: '2012-10-17',
              Statement: [
                {
                  Effect: 'Allow',
                  Action: ['lambda:InvokeFunction'],
                  Resource: '*'
                }
              ]
            }
          }
        ]
      }
    },
    MyStateMachine: {
      Type: 'AWS::StepFunctions::StateMachine',
      Properties: {
        DefinitionString: cf.sub(
          stringifyDefinition({
            Comment: 'A Hello World AWL example using an AWS Lambda function',
            StartAt: 'HelloWorld',
            States: {
              HelloWorld: {
                Type: 'Task',
                Resource: '${lambdaArn}',
                End: true
              }
            }
          }),
          {
            lambdaArn: cf.getAtt('MyLambdaFunction', 'Arn')
          }
        ),
        RoleArn: cf.getAtt('StatesExecutionRole', 'Arn')
      }
    }
  }
};