cloudformation

# AWS CloudFormation AWS CloudFormation provisions and manages AWS resources using templates. Define infrastructure as code, version control it, and deploy consistently across environments. ## Table of Contents - [Core Concepts](#core-concepts) - [Common Patterns](#common-patterns) - [CLI Reference](#cli-reference) - [Best Practices](#best-practices) - [Troubleshooting](#troubleshooting) - [References](#references) ## Core Concepts ### Templates JSON or YAML files defining AWS resources. Key sections: - **Parameters**: Input values - **Mappings**: Static lookup tables - **Conditions**: Conditional resource creation - **Resources**: AWS resources (required) - **Outputs**: Return values ### Stacks Collection of resources managed as a single unit. Created from templates. ### Change Sets Preview changes before executing updates. ### Stack Sets Deploy stacks across multiple accounts and regions. ## Common Patterns ### Basic Template Structure ```yaml AWSTemplateFormatVersion: '2010-09-09' Description: My infrastructure template Parameters: Environment: Type: String AllowedValues: [dev, staging, prod] Default: dev Mappings: EnvironmentConfig: dev: InstanceType: t3.micro prod: InstanceType: t3.large Conditions: IsProd: !Equals [!Ref Environment, prod] Resources: MyBucket: Type: AWS::S3::Bucket Properties: BucketName: !Sub 'my-app-${Environment}-${AWS::AccountId}' VersioningConfiguration: Status: !If [IsProd, Enabled, Suspended] Outputs: BucketName: Description: S3 bucket name Value: !Ref MyBucket Export: Name: !Sub '${AWS::StackName}-BucketName' ``` ### Deploy a Stack **AWS CLI:** ```bash # Create stack aws cloudformation create-stack \ --stack-name my-stack \ --template-body file://template.yaml \ --parameters ParameterKey=Environment,ParameterValue=prod \ --capabilities CAPABILITY_IAM # Wait for completion aws cloudformation wait stack-create-complete --stack-name my-stack # Update stack aws cloudformation update-stack \ --stack-name my-stack \ --template-body file://template.yaml \ --parameters ParameterKey=Environment,ParameterValue=prod # Delete stack aws cloudformation delete-stack --stack-name my-stack ``` ### Use Change Sets ```bash # Create change set aws cloudformation create-change-set \ --stack-name my-stack \ --change-set-name my-changes \ --template-body file://template.yaml \ --parameters ParameterKey=Environment,ParameterValue=prod # Describe changes aws cloudformation describe-change-set \ --stack-name my-stack \ --change-set-name my-changes # Execute change set aws cloudformation execute-change-set \ --stack-name my-stack \ --change-set-name my-changes ``` ### Lambda Function ```yaml Resources: LambdaFunction: Type: AWS::Lambda::Function Properties: FunctionName: !Sub '${AWS::StackName}-function' Runtime: python3.12 Handler: index.handler Role: !GetAtt LambdaRole.Arn Code: ZipFile: | def handler(event, context): return {'statusCode': 200, 'body': 'Hello'} Environment: Variables: ENVIRONMENT: !Ref Environment LambdaRole: Type: AWS::IAM::Role Properties: AssumeRolePolicyDocument: Version: '2012-10-17' Statement: - Effect: Allow Principal: Service: lambda.amazonaws.com Action: sts:AssumeRole ManagedPolicyArns: - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole ``` ### VPC with Subnets ```yaml Resources: VPC: Type: AWS::EC2::VPC Properties: CidrBlock: 10.0.0.0/16 EnableDnsHostnames: true Tags: - Key: Name Value: !Sub '${AWS::StackName}-vpc' PublicSubnet1: Type: AWS::EC2::Subnet Properties: VpcId: !Ref VPC AvailabilityZone: !Select [0, !GetAZs ''] CidrBlock: 10.0.1.0/24 MapPublicIpOnLaunch: true PrivateSubnet1: Type: AWS::EC2::Subnet Properties: VpcId: !Ref VPC AvailabilityZone: !Select [0, !GetAZs ''] CidrBlock: 10.0.10.0/24 InternetGateway: Type: AWS::EC2::InternetGateway AttachGateway: Type: AWS::EC2::VPCGatewayAttachment Properties: VpcId: !Ref VPC InternetGatewayId: !Ref InternetGateway PublicRouteTable: Type: AWS::EC2::RouteTable Properties: VpcId: !Ref VPC PublicRoute: Type: AWS::EC2::Route DependsOn: AttachGateway Properties: RouteTableId: !Ref PublicRouteTable DestinationCidrBlock: 0.0.0.0/0 GatewayId: !Ref InternetGateway PublicSubnet1RouteTableAssociation: Type: AWS::EC2::SubnetRouteTableAssociation Properties: SubnetId: !Ref PublicSubnet1 RouteTableId: !Ref PublicRouteTable ``` ### DynamoDB Table ```yaml Resources: OrdersTable: Type: AWS::DynamoDB::Table Properties: TableName: !Sub '${AWS::StackName}-orders' AttributeDefinitions: - AttributeName: PK AttributeType: S - AttributeName: SK AttributeType: S - AttributeName: GSI1PK AttributeType: S - AttributeName: GSI1SK AttributeType: S KeySchema: - AttributeName: PK KeyType: HASH - AttributeName: SK KeyType: RANGE GlobalSecondaryIndexes: - IndexName: GSI1 KeySchema: - AttributeName: GSI1PK KeyType: HASH - AttributeName: GSI1SK KeyType: RANGE Projection: ProjectionType: ALL BillingMode: PAY_PER_REQUEST PointInTimeRecoverySpecification: PointInTimeRecoveryEnabled: true ``` ## CLI Reference ### Stack Operations | Command | Description | |---------|-------------| | `aws cloudformation create-stack` | Create stack | | `aws cloudformation update-stack` | Update stack | | `aws cloudformation delete-stack` | Delete stack | | `aws cloudformation describe-stacks` | Get stack info | | `aws cloudformation list-stacks` | List stacks | | `aws cloudformation describe-stack-events` | Get events | | `aws cloudformation describe-stack-resources` | Get resources | ### Change Sets | Command | Description | |---------|-------------| | `aws cloudformation create-change-set` | Create change set | | `aws cloudformation describe-change-set` | View changes | | `aws cloudformation execute-change-set` | Apply changes | | `aws cloudformation delete-change-set` | Delete change set | ### Template | Command | Description | |---------|-------------| | `aws cloudformation validate-template` | Validate template | | `aws cloudformation get-template` | Get stack template | | `aws cloudformation get-template-summary` | Get template info | ## Best Practices ### Template Design - **Use parameters** for environment-specific values - **Use mappings** for static lookup tables - **Use conditions** for optional resources - **Export outputs** for cross-stack references - **Add descriptions** to parameters and outputs ### Security - **Use IAM roles** instead of access keys - **Enable termination protection** for production - **Use stack policies** to protect resources - **Never hardcode secrets** — use Secrets Manager ```bash # Enable termination protection aws cloudformation update-termination-protection \ --stack-name my-stack \ --enable-termination-protection ``` ### Organization - **Use nested stacks** for complex infrastructure - **Create reusable modules** - **Version control templates** - **Use consistent naming conventions** ### Reliability - **Use DependsOn** for explicit dependencies - **Configure creation policies** for instances - **Use update policies** for Auto Scaling groups - **Implement rollback triggers** ## Troubleshooting ### Stack Creation Failed ```bash # Get failure reason aws cloudformation describe-stack-events \ --stack-name my-stack \ --query 'StackEvents[?ResourceStatus==`CREATE_FAILED`]' # Common causes: # - IAM permissions # - Resource limits # - Invalid property values # - Dependency failures ``` ### Stack Stuck in DELETE_FAILED ```bash # Identify resources that couldn't be deleted aws cloudformation describe-stack-resources \ --stack-name my-stack \ --query 'StackResources[?ResourceStatus==`DELETE_FAILED`]' # Retry with resources to skip aws cloudformation delete-stack \ --stack-name my-stack \ --retain-resources ResourceLogicalId1 ResourceLogicalId2 ``` ### Drift Detection ```bash # Detect drift aws cloudformation detect-stack-drift --stack-name my-stack # Check drift status aws cloudformation describe-stack-drift-detection-status \ --stack-drift-detection-id abc123 # View drifted resources aws cloudformation describe-stack-resource-drifts \ --stack-name my-stack ``` ### Rollback Failed ```bash # Continue update rollback aws cloudformation continue-update-rollback \ --stack-name my-stack \ --resources-to-skip ResourceLogicalId1 ``` ## References - [CloudFormation User Guide](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/) - [CloudFormation API Reference](https://docs.aws.amazon.com/AWSCloudFormation/latest/APIReference/) - [CloudFormation CLI Reference](https://docs.aws.amazon.com/cli/latest/reference/cloudformation/) - [Resource and Property Reference](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html)