CloudFormation

Introduction

  • IaC in AWS

  • Portability of stacks across multiple accounts and regions

  • Backbone of:

    • Elastic Beanstalk

    • Service Catalog

    • SAM (Serverless Application Model) framework

Feature

  • CloudFormation with ASG

    • CloudFormation manages the ASG, not the underlying EC2

    • Can define "success condition" for the lauch of EC2 instances useing a CreationPolicy

    • Can define "update strategies" for the update of EC2 instances using an UpdatePolicy

    • To update the underlying EC2 in an ASG, you have to create a new launch configuration / launch template & use an UpdatePolicy

  • Retain data on deletes

    • Can put a DeletionPolicy on any resource to control what happens when the CloudFormation template is deleted.

    • DeleteionPolicy Options:

      • Retain

        • Specify on resources to preserve / backup in case of CloudFormation deletes

        • To keep a resource, specify Retain (works for any resource / nested stack)

      • Snapshot

        • EBS Volume

        • ElastiCache Cluster / ReplicationGroup

        • RDS Cluster / Instance

        • Redshift Cluster

      • Delete (default mostly)

        • RDS Cluster default policy: Snapshot

        • S3 bucket must be empty to perform deletion

  • IAM

    • Permission for execution options:

      • With your IAM permission

      • Assign an IAM Role to the stack to perform actions

    • Creating IAM resources

      • Need to explicitly provide a "capability" to CloudFormation CAPABILITY_IAM or CAPABILITY_NAMED_IAM

    • Reference IAM Role to EC2 instances

      • Assign with the InstanceProfileName property

  • Custom Resources

    • With Lambda to program anything you want. To be called by CloudFormation.

  • Cross vs Nested Stacks

    • Cross Stacks

      • Helpful when stacks have different lifecycles

      • Work with Outputs Export and Fn::ImportValue

    • Nested Stacks

      • Helpful when components must be re-used

  • CloudFormer

    • Create an AWS CloudFormation template from existing AWS resources

  • ChangeSets

    • Generate & preview the CloudFormation changes before applying

  • StackSets

    • Deploy a CloudFormation stack to provision stack resources across multiple accounts and regions

  • Stack Policies

    • Prevent accidental updates / deletes to stack resources

  • Tempates

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