AWS CloudFormation

• A service that gives developers and businesses an easy way to create a collection of related AWS resources and provision them in an orderly and predictable fashion.

Features

• CloudFormation allows you to model your entire infrastructure in a text file called a template. You can use JSON or YAML to describe what AWS resources you want to create and configure. If you want to design visually, you can use AWS CloudFormation Designer.
• CloudFormation automates the provisioning and updating of your infrastructure in a safe and controlled manner. You can use Rollback Triggers to specify the CloudWatch alarm that CloudFormation should monitor during the stack creation and update process. If any of the alarms are breached, CloudFormation rolls back the entire stack operation to a previous deployed state.
• CloudFormation Change Sets allow you to preview how proposed changes to a stack might impact your running resources.
• AWS StackSets lets you provision a common set of AWS resources across multiple accounts and regions with a single CloudFormation template. StackSets takes care of automatically and safely provisioning, updating, or deleting stacks in multiple accounts and across multiple regions.
• CloudFormation enables you to build custom extensions to your stack template using AWS Lambda.

CloudFormation vs Elastic Beanstalk

• Elastic Beanstalk provides an environment to easily deploy and run applications in the cloud.
• CloudFormation is a convenient provisioning mechanism for a broad range of AWS resources.

Concepts

• Templates
• • A JSON or YAML formatted text file.
  • CloudFormation uses these templates as blueprints for building your AWS resources.
• Stacks
• • Manage related resources as a single unit.
  • All the resources in a stack are defined by the stack’s CloudFormation template.
• Change Sets
• • Before updating your stack and making changes to your resources, you can generate a change set, which is a summary of your proposed changes.
  • Change sets allow you to see how your changes might impact your running resources, especially for critical resources, before implementing them.

• With AWS CloudFormation and AWS CodePipeline, you can use continuous delivery to automatically build and test changes to your CloudFormation templates before promoting them to production stacks.
• CloudFormation artifacts can include a stack template file, a template configuration file, or both. AWS CodePipeline uses these artifacts to work with CloudFormation stacks and change sets.
  • Stack Template File – defines the resources that CloudFormation provisions and configures. You can use YAML or JSON-formatted templates.
  • Template Configuration File – a JSON-formatted text file that can specify template parameter values, a stack policy, and tags. Use these configuration files to specify parameter values or a stack policy for a stack.

Stacks

• If a resource cannot be created, CloudFormation rolls the stack back and automatically deletes any resources that were created. If a resource cannot be deleted, any remaining resources are retained until the stack can be successfully deleted.
• Stack update methods
  • Direct update
  • Creating and executing change sets
• Drift detection enables you to detect whether a stack’s actual configuration differs, or has drifted, from its expected configuration. Use CloudFormation to detect drift on an entire stack, or on individual resources within the stack.
  • A resource is considered to have drifted if any if its actual property values differ from the expected property values.
  • A stack is considered to have drifted if one or more of its resources have drifted.
• To share information between stacks, export a stack’s output values. Other stacks that are in the same AWS account and region can import the exported values.
• You can nest stacks.

Templates

• Templates include several major sections. The Resources section is the only required section.
• CloudFormation Designer is a graphic tool for creating, viewing, and modifying CloudFormation templates. You can diagram your template resources using a drag-and-drop interface, and then edit their details using the integrated JSON and YAML editor.
• Custom resources enable you to write custom provisioning logic in templates that CloudFormation runs anytime you create, update (if you changed the custom resource), or delete stacks.
• Template macros enable you to perform custom processing on templates, from simple actions like find-and-replace operations to extensive transformations of entire templates.

StackSets

• Administrator and target accounts – An administrator account is the AWS account in which you create stack sets. A stack set is managed by signing in to the AWS administrator account in which it was created. A target account is the account into which you create, update, or delete one or more stacks in your stack set.
• Stack sets – A stack set lets you create stacks in AWS accounts across regions by using a single CloudFormation template. All the resources included in each stack are defined by the stack set’s CloudFormation template. A stack set is a regional resource.
• Stack instances – A stack instance is a reference to a stack in a target account within a region. A stack instance can exist without a stack, and can be associated with only one stack set.
• Stack set operations – Create stack set, update stack set, delete stacks, and delete stack set.
• Tags – You can add tags during stack set creation and update operations by specifying key and value pairs.

Monitoring

• CloudFormation is integrated with AWS CloudTrail, a service that provides a record of actions taken by a user, role, or an AWS service in CloudFormation. CloudTrail captures all API calls for CloudFormation as events, including calls from the CloudFormation console and from code calls to the CloudFormation APIs.

Security

• You can use IAM with CloudFormation to control what users can do with AWS CloudFormation, such as whether they can view stack templates, create stacks, or delete stacks.
• A service role is an IAM role that allows CloudFormation to make calls to resources in a stack on your behalf. You can specify an IAM role that allows CloudFormation to create, update, or delete your stack resources.
• You can improve the security posture of your VPC by configuring CloudFormation to use an interface VPC endpoint.

Pricing

• No additional charge for CloudFormation. You pay for AWS resources created using CloudFormation in the same manner as if you created them manually.

Limits

Limit	Description	Value
Resources	Maximum number of resources that you can declare in your CloudFormation template.	200 resources
Stacks	Maximum number of CloudFormation stacks that you can create.	200 stacks
StackSets	Maximum number of CloudFormation stack sets you can create in your administrator account.	20 stack sets

Sources:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/
https://aws.amazon.com/cloudformation/features/
https://aws.amazon.com/cloudformation/pricing/
https://aws.amazon.com/cloudformation/faqs/

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