CloudFormation

Overview

CloudFormation is a powerful Infrastructure as Code (IaC) service that enables automated and repeatable deployment of AWS resources. It allows organizations to model and provision entire cloud environments using template files in JSON or YAML format.

Key Features

Infrastructure as Code

• Template-based infrastructure deployment

• Supports both JSON and YAML formats

• Automated deployments and rollbacks

• Nested components for reusability

• Over 300 supported resource types

• Custom resource creation via SNS or Lambda

Core Components

Templates

• Text files containing infrastructure definitions

• Written in JSON or YAML

• Define all aspects of the AWS environment

• Only required section is "Resources"

• Can include multiple AWS services and configurations

Stacks

• Represents the entire environment described by a template

• Managed as a single unit

• Can be created or destroyed together

• Maintains consistent state across resources

Change Sets

• Preview of proposed stack modifications

• Analysis of potential implications

• Helps identify unintended changes

• Risk assessment tool for stack updates

Stack Policies

Purpose

• Protect resources from accidental modification

• Prevent unintended deletions or updates

• Safeguard critical infrastructure components

• Especially useful for production databases

Implementation Details

• Can be added via console or CLI during stack creation

• Post-creation additions only possible through CLI

• Cannot be removed once applied

• Can be modified as needed

Default Behavior

• Protects all resources by default

• Requires explicit allow statements for updates

• Must specifically define allowed actions

• Deny rules override allow rules

Best Practices

Helper Scripts

• Use AWS-provided Python helper scripts

• Automate software installation

• Configure services on EC2 instances

• Streamline post-deployment configuration

Change Management

• Make changes through templates rather than direct resource modification

• Use change sets to identify potential issues

• Maintain template version control

• Document all modifications

Version Control

• Use systems like GitHub or CodeCommit

• Track template changes

• Maintain history of modifications

• Enable collaboration and rollback

Stack Protection

• Implement stack policies for critical resources

• Define explicit protection rules

• Regular policy review and updates

• Document protected resources

Template Management

• Keep templates modular

• Use nested stacks for reusable components

• Maintain consistent naming conventions

• Regular template validation

Resource Configuration Example

Resources:
  EC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: ami-xxxxx
      KeyName: my-key
      BlockDeviceMappings:
        - DeviceName: /dev/sda1
          Ebs:
            VolumeSize: 50

Scaling Policy Example

ScalingPolicy:
  Type: AWS::AutoScaling::ScalingPolicy
  Properties:
    AdjustmentType: ChangeInCapacity
    AutoScalingGroupName: !Ref AutoScalingGroup
    Cooldown: '300'
    ScalingAdjustment: 1

CloudWatchAlarm:
  Type: AWS::CloudWatch::Alarm
  Properties:
    AlarmDescription: Scale-up if CPU > 90% for 10 minutes
    MetricName: CPUUtilization
    Namespace: AWS/EC2
    Statistic: Average
    Period: 300
    EvaluationPeriods: 2
    Threshold: 90
    AlarmActions:
      - !Ref ScalingPolicy

Implementation Considerations

Deployment Strategy

• Plan stack organization

• Consider resource dependencies

• Account for scaling requirements

• Design for disaster recovery

Security

• Implement least privilege access

• Use stack policies effectively

• Encrypt sensitive parameters

• Regular security audits

Monitoring

• Track stack events

• Monitor resource creation

• Set up alerts for failures

• Regular compliance checks

Cost Management

• Review resource provisions

• Monitor stack costs

• Implement tagging strategy

• Regular cost optimization