CloudFormation

CloudFormation (Infrastructure as a Service)

JSON or YAML
Base entity : Stacks tied with resources for creation, update, deletion
Required: Resource definition

Template Portability and Reuse

• Parameters with default values or no parameters at all
• Pull the values from System Manager Parameter Store
• Pseudo Parameters (eg: AWS::Region, Partition, StackId, StackName, URLSuffix etc)
• Intrinsic Functions (eg: Fn::GetAZs, Fn::ImportValue, Ref etc)

Cross stack references

• Base Infrastructure values like VPCId, subnets, can be referenced in other stacks
• Using Ref, Export, Fn::ImportValue
• Reuse Stacks

Nested Stacks

• Reuse blocks of CloudFormation templates.
• Reuse same template code but create multiple different stacks with the same template.
• Share outputs with parameters between these stacks using nested stacks.
  eg: GetAtt ‘VPCStack.Outputs.VPCID’

Stack Roles

• Allows anyone to use CloudFormation provision,update delete based on the roles permissions.
• Allows separate security rules.
• Its IAM Role -> AWS Service -> CloudFormation Role

Stack Sets

• Administrator Account and a Target Account
• Allow you to deploy a cloudformation template into multiple regions or
• Multiple regions in multiple accounts at the same time.
• You need to establish a trust between these accounts by creating 2 roles:
• AWSCloudFormationStackSetAdminRole in Admin Account and
• AWSCloudFormationStackSetExecutionRole in Target Account. eg: Enable cloudtrail across multiple accounts, enable mfa accross multiple accounts etc.

Custom Resources

• Custom Resource in CloudFormation Template.
• Used in scenarios when you want to build Hybrid Infrastructure (Both AWS and Outside AWS) (eg: Retrieve a license key to activate)
• CloudFormation Sends a notification event to a lambda or SNS topic
• Define
  • Custom::AMIInfo
  • ServiceToken : is the endpoint of lambda or SNS topic
• Receives Response on a pre-signed S3 URL

CloudFormer tool is used to create CloudFormation template files from existing stack.
CloudFormation can be used as one of the Disaster Recovery Strategies.