Config.Tips

Modularize AWS CloudFormation Templates

In this example, a reusable module for Amazon S3 bucket is created with its own template in s3-module.yaml. The Main Stack Template creates two buckets using same template.

Modularizing the AWS S3 Bucket creation into a separate template and reusing it in the main stack promotes code reusability and maintainability. Additional S3 buckets can easily be added by including additional stack resources in the main template without duplicating the S3 configuration code.

  1. S3 Bucket Module (s3-module.yaml): This template defines a reusable S3 Bucket Module with configurable parameters: BucketName and AccessControl.The template is uploaded into an S3 bucket so that it can be accessed in the Main Stack Template.

    ```yaml
Parameters:
BucketName:
    Type: String
    Description: Name for the S3 bucket
AccessControl:
    Type: String
    Description: Access control for the bucket
    Default: private
    AllowedValues:
    - private
    - public-read
```

  2. Main Stack Template main-template.yaml: In the main-template.yaml, the same S3 Bucket Module is used twice to create two separate buckets. Both buckets reference the same S3 module using the TemplateURL key:

    TemplateURL: 'https://s3.amazonaws.com/your-bucket/s3-module.yaml'

For more details, you can refer to the AWS CloudFormation documentation.

cloudformation-template.yml
# s3-module.yaml
AWSTemplateFormatVersion: '2010-09-09'
Description: S3 Bucket Module

Parameters:
    BucketName:
    Type: String
    Description: Name for the S3 bucket
    AccessControl:
    Type: String
    Description: Access control for the bucket (e.g., private, public-read)
    Default: private
    AllowedValues:
        - private
        - public-read

Resources:
    MyS3Bucket:
    Type: AWS::S3::Bucket
    Properties:
        BucketName: !Ref BucketName
        AccessControl: !Ref AccessControl

# main-template.yaml
AWSTemplateFormatVersion: '2010-09-09'
Description: Main Stack Template

Resources:
    MyPrivateBucket:
    Type: AWS::CloudFormation::Stack
    Properties:
        TemplateURL: 'https://s3.amazonaws.com/your-bucket/s3-bucket.yaml'
        Parameters:
        BucketName: my-private-bucket
        AccessControl: private

    MyPublicBucket:
    Type: AWS::CloudFormation::Stack
    Properties:
        TemplateURL: 'https://s3.amazonaws.com/your-bucket/s3-bucket.yaml'
        Parameters:
        BucketName: my-public-bucket
        AccessControl: public-read

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