aws cloudformation - sharing stack outputs with other stacks

We can share stacks outputs from one deployment with another separate deployment. Let's say we create a s3 store stack with outputs. Then we can use this output as input for another stack app stack later. 

To see this in action, let create a "storage.yaml" s3 stack as shown here

AWSTemplateFormatVersion: '2010-09-09'

Description: Storage stack exporting an S3 bucket name and ARN

Resources:

  MyDataBucket:

    Type: AWS::S3::Bucket

    Properties:

      BucketName: !Sub "my-data-bucket-${AWS::AccountId}"

Outputs:

  BucketName:

    Value: !Ref MyDataBucket

    Export:

      Name: !Sub "${AWS::StackName}-BucketName"

  BucketArn:

    Value: !GetAtt MyDataBucket.Arn

    Export:

      Name: !Sub "${AWS::StackName}-BucketArn"

Then deploy it:

aws cloudformation create-stack \

  --stack-name storageStack \

--region ap-southeast-2 \

  --template-body file://storage.yaml

Next we will create the app stack, called app.yaml

AWSTemplateFormatVersion: '2010-09-09'

Description: App stack importing an S3 bucket export from storageStack

Parameters:

  StorageStackName:

    Type: String

    Default: storageStack

    Description: Name of the stack that created and exported the S3 bucket

Resources:

  AppRole:

    Type: AWS::IAM::Role

    Properties:

      RoleName: my-app-role

      AssumeRolePolicyDocument:

        Version: "2012-10-17"

        Statement:

          - Effect: Allow

            Principal:

              Service: lambda.amazonaws.com

            Action: sts:AssumeRole

      Policies:

        - PolicyName: AccessImportedBucket

          PolicyDocument:

            Version: "2012-10-17"

            Statement:

              - Effect: Allow

                Action:

                  - s3:GetObject

                  - s3:PutObject

                Resource:

                  # Allow access to bucket and all objects

                  - !ImportValue

                      'Fn::Sub': "${StorageStackName}-BucketArn"

                  - !Sub

                      - "${BucketArn}/*"

                      -

                        BucketArn:

                          !ImportValue

                            'Fn::Sub': "${StorageStackName}-BucketArn"

Outputs:

  ImportedBucketArn:

    Description: The ARN of the imported S3 bucket

    Value: !ImportValue

      'Fn::Sub': "${StorageStackName}-BucketArn"

Next we will create the app stack by running this command:- 

aws cloudformation create-stack \

  --stack-name appStack \

  --region ap-southeast-2 \

  --capabilities CAPABILITY_NAMED_IAM \

  --template-body file://app.yaml

And you can see the final output from here