aws-cloudformation-cloudfront

AWS CloudFormation CloudFront CDN

Overview

Create production-ready CDN infrastructure using AWS CloudFormation templates. This skill covers CloudFront distributions, multiple origins (ALB, S3, API Gateway, Lambda@Edge, VPC Origins), CacheBehaviors, Functions, SecurityHeaders, and best practices for parameters, outputs, and cross-stack references.

When to Use

• Creating CloudFront distributions with CloudFormation
• Configuring origins (ALB, S3, Lambda@Edge, VPC Origins) with path patterns
• Implementing caching with CacheBehaviors and Cache Policies
• Configuring custom domains with ACM and SecurityHeaders
• Integrating WAF with CloudFront distributions

Instructions

Follow these steps to create CloudFront distributions with CloudFormation:

1. Define Distribution Parameters

Validate before deploying:

aws cloudformation validate-template --template-body file://template.yaml
cfn-lint template.yaml

Specify domain names, ACM certificates, price class, and origin settings:

Parameters:
  DomainName:
    Type: String
    Default: cdn.example.com
    Description: Custom domain name for CloudFront distribution

  CertificateArn:
    Type: AWS::ACM::Certificate::Arn
    Description: ACM certificate ARN for HTTPS

  PriceClass:
    Type: String
    Default: PriceClass_All
    AllowedValues:
      - PriceClass_All
      - PriceClass_100
      - PriceClass_200
    Description: CloudFront price class

  OriginDomainName:
    Type: String
    Description: Domain name of the origin (ALB or S3)

2. Configure Origins

Add S3 buckets, ALBs, API Gateway, or custom origins. For S3 origins, use OAI (legacy) or OAC (recommended):

Resources:
  # S3 Bucket
  StaticBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Sub "static-assets-${AWS::AccountId}-${AWS::Region}"
      PublicAccessBlockConfiguration:
        BlockPublicAcls: true
        BlockPublicPolicy: true

  # Origin Access Control (recommended)
  OriginAccessControl:
    Type: AWS::CloudFront::OriginAccessControl
    Properties:
      OriginAccessControlConfig:
        Name: !Sub "${AWS::StackName}-oac"
        OriginAccessControlOriginType: s3
        SigningBehavior: always
        SigningProtocol: sigv4

3. Set Up Default Cache Behavior

Configure viewer request/response policies and caching:

Resources:
  CloudFrontDistribution:
    Type: AWS::CloudFront::Distribution
    Properties:
      DistributionConfig:
        Origins:
          - Id: S3Origin
            DomainName: !GetAtt StaticBucket.RegionalDomainName
            AccessControlId: !Ref OriginAccessControl
            S3OriginConfig:
              OriginAccessIdentity: ""
        DefaultCacheBehavior:
          TargetOriginId: S3Origin
          ViewerProtocolPolicy: redirect-to-https
          AllowedMethods:
            - GET
            - HEAD
          CachedMethods:
            - GET
            - HEAD
          Compress: true
          CachePolicyId: !Ref CachePolicy

4. Add Additional Cache Behaviors

Create path-specific caching rules for different content types:

Resources:
  ApiCachePolicy:
    Type: AWS::CloudFront::CachePolicy
    Properties:
      CachePolicyConfig:
        Name: !Sub "${AWS::StackName}-api-cache"
        DefaultTTL: 300
        MaxTTL: 600
        MinTTL: 60

  CloudFrontDistribution:
    Type: AWS::CloudFront::Distribution
    Properties:
      DistributionConfig:
        CacheBehaviors:
          - PathPattern: "/api/*"
            TargetOriginId: ApiOrigin
            CachePolicyId: !GetAtt ApiCachePolicy.Id
            AllowedMethods:
              - GET
              - HEAD
              - OPTIONS
              - PUT
              - POST

5. Configure Security Settings

Implement security headers and WAF integration:

Resources:
  SecurityHeadersPolicy:
    Type: AWS::CloudFront::ResponseHeadersPolicy
    Properties:
      ResponseHeadersPolicyConfig:
        Name: !Sub "${AWS::StackName}-security-headers"
        SecurityHeadersConfig:
          StrictTransportSecurity:
            AccessControlMaxAgeSec: 31536000
            IncludeSubdomains: true
            Override: true
          FrameOptions:
            FrameOption: DENY
            Override: true

  WAFWebACL:
    Type: AWS::WAFv2::WebACL
    Properties:
      Name: !Sub "${AWS::StackName}-waf"
      Scope: CLOUDFRONT
      DefaultAction:
        Allow: {}

6. Add CloudFront Functions

Configure functions for request/response manipulation:

Resources:
  RewritePathFunction:
    Type: AWS::CloudFront::Function
    Properties:
      Name: !Sub "${AWS::StackName}-rewrite-path"
      FunctionCode: |
        function handler(event) {
          var request = event.request;
          // Function code here
          return request;
        }
      Runtime: cloudfront-js-1.0
      AutoPublish: true

7. Configure Monitoring

Set up logging and access logs to S3:

Resources:
  AccessLogsBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Sub "cloudfront-logs-${AWS::AccountId}"

  CloudFrontDistribution:
    Type: AWS::CloudFront::Distribution
    Properties:
      DistributionConfig:
        Logging:
          Bucket: !Ref AccessLogsBucket
          Prefix: cloudfront-logs/
          IncludeCookies: false

8. Create Outputs

Export distribution details for cross-stack references:

Outputs:
  DistributionDomainName:
    Description: CloudFront distribution domain name
    Value: !GetAtt CloudFrontDistribution.DomainName
    Export:
      Name: !Sub "${AWS::StackName}-DistributionDomainName"

  DistributionId:
    Description: CloudFront distribution ID
    Value: !Ref CloudFrontDistribution
    Export:
      Name: !Sub "${AWS::StackName}-DistributionId"

Best Practices

Security

• Always use HTTPS with minimum TLS 1.2
• Implement SecurityHeaders with HSTS, XSS protection
• Use WAF for protection against common attacks
• Configure appropriate Access-Control for CORS
• Limit origin access with OAI/OAC
• Use Signed URLs for private content
• Implement rate limiting
• Configure geo-restrictions if needed

Performance

• Use appropriate PriceClass to optimize costs
• Configure Cache TTL based on content type
• Enable compression (Gzip/Brotli)
• Use CloudFront Functions for lightweight operations
• Optimize header forwarding (do not forward unnecessary headers)
• Consider Origin Shield to reduce load on origins
• Use multiple origins with path patterns

Monitoring

• Enable CloudWatch metrics and alarms
• Configure real-time logs for troubleshooting
• Monitor cache hit ratio
• Configure alerts for error rate and latency
• Use CloudFront reports for traffic analysis

Deployment

• Use change sets before deployment
• Test templates with cfn-lint
• Organize stacks by lifecycle and ownership
• Implement blue/green deployments with weighted aliases
• Use StackSets for multi-region deployment

Template Structure

• Use AWS-specific parameter types (AWS::ACM::Certificate::Arn, AWS::S3::Bucket::RegionalDomainName)
• Implement parameter constraints (MinLength, MaxLength, AllowedValues, AllowedPattern)
• Use Conditions for environment-specific configuration
• Leverage Mappings for region-specific configuration
• Apply Metadata for parameter grouping and labels
• Use nested stacks for modularity

Cache Strategy

• Use Cache Policies for different content types
• Configure Origin Request Policies to control what's sent to origin
• Set appropriate TTL values:
• Static assets: 86400-31536000 seconds (1 day to 1 year)
• API responses: 60-600 seconds (1-10 minutes)
• Dynamic content: 0 seconds (no caching)
• Enable compression for text-based content
• Use versioned paths for cache busting

Constraints and Warnings

• ACM certificates: Must be in us-east-1 (N. Virginia) for CloudFront
• Limits: Max 200 distributions per AWS account, 25 origins pe