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Welcome to the next lesson. In this lesson we’ll review the optional CloudFormation resource attributes you can use to control configuration, lifecycle, and conditional creation of resources. These attributes let you customize how resources are created, updated, or deleted, and how they participate in stack operations. Key optional attributes covered here:
  • Properties — Defines the resource configuration (size, tags, names, and resource-specific settings).
  • Metadata — Arbitrary data attached to a resource for tooling or helper scripts (for example, cfn-init).
  • DependsOn — Ensures a creation or deletion order by specifying one or more resources that must be processed first.
A presentation slide titled "Optional Attributes for Resources." It lists three attributes—Properties, Metadata, and DependsOn—with brief descriptions about resource configuration, additional information, and controlling creation order in CloudFormation.
Other important optional attributes:
  • DeletionPolicy — Controls what happens to a resource when its stack is deleted. Common values:
    • Delete — removes the resource (default).
    • Retain — keeps the resource after stack deletion.
    • Snapshot — creates a snapshot for snapshot-capable resources (for example, RDS DB instances and EBS volumes) before deletion.
  • UpdatePolicy — Controls how CloudFormation updates certain resources during stack updates (for example, AutoScaling rolling updates).
  • Condition — Only creates a resource if a named condition (defined under the template’s Conditions section) evaluates to true. Useful for region-specific or parameter-driven resource inclusion.
Summary table of optional resource attributes
AttributePurposeTypical use case / example
PropertiesConfigure the resourceBucketName, InstanceType, Tags
MetadataAttach arbitrary data for toolingAWS::CloudFormation::Init configuration for cfn-init
DependsOnControl creation/deletion orderEnsure DB creation occurs after VPC or Subnet
DeletionPolicyControl behavior on stack deletionRetain to keep an S3 bucket after stack deletion
UpdatePolicyControl update behaviorAutoScalingRollingUpdate for AWS::AutoScaling::AutoScalingGroup
ConditionCreate resource only if condition is trueEnvironment-specific resources (prod vs dev)
Detailed examples and usage
  1. Properties — resource configuration Most resource types require a Properties object to configure details such as names, sizes, and tags.
Example (S3 bucket with tags): 
Resources:
  MyBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-app-bucket
      Tags:
        - Key: Environment
          Value: Production
  1. Metadata — attach tooling data (cfn-init example) Metadata is not processed by CloudFormation directly but is commonly used by helper tools like cfn-init to configure instances.
Example (EC2 instance metadata for cfn-init): 
Resources:
  WebServer:
    Type: AWS::EC2::Instance
    Metadata:
      AWS::CloudFormation::Init:
        config:
          packages:
            yum:
              httpd: []
          files:
            /var/www/html/index.html:
              content: "<html>Hello from cfn-init</html>"
    Properties:
      InstanceType: t3.micro
      ImageId: ami-0123456789abcdef0
  1. DependsOn — control creation/deletion order DependsOn ensures one resource is created or deleted after another. It accepts either a single logical name or a list of logical names.
Example: 
Resources:
  DBSubnetGroup:
    Type: AWS::RDS::DBSubnetGroup
    Properties:
      DBSubnetGroupDescription: Subnet group for RDS
      SubnetIds:
        - subnet-aaa
        - subnet-bbb

  MyDBInstance:
    Type: AWS::RDS::DBInstance
    DependsOn: DBSubnetGroup
    Properties:
      DBInstanceClass: db.t3.micro
      Engine: mysql
  1. DeletionPolicy — keep or snapshot resources on stack deletion Use DeletionPolicy to retain critical resources or create snapshots before deletion.
Example (retain S3 bucket and snapshot an RDS instance): 
Resources:
  BackupBucket:
    Type: AWS::S3::Bucket
    DeletionPolicy: Retain
    Properties:
      BucketName: my-backup-bucket

  Database:
    Type: AWS::RDS::DBInstance
    DeletionPolicy: Snapshot
    Properties:
      DBInstanceClass: db.t3.micro
      Engine: mysql
Using DeletionPolicy:Retain or leaving resources after stack deletion may incur ongoing charges. Verify any retained resources to avoid unexpected costs.
  1. UpdatePolicy — control update behavior for specific resource types UpdatePolicy applies to a limited set of resource types (for example Auto Scaling groups). Use it to manage rolling updates and replacement behavior.
Example (Auto Scaling group rolling update policy): 
Resources:
  MyAutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      MinSize: "1"
      MaxSize: "3"
      LaunchConfigurationName: !Ref MyLaunchConfig
    UpdatePolicy:
      AutoScalingRollingUpdate:
        MinInstancesInService: 1
        MaxBatchSize: 1
        PauseTime: PT5M
  1. Condition — create resources conditionally Define Conditions in the template and attach them to resources using the Condition attribute.
Example: 
Parameters:
  DeployProd:
    Type: String
    AllowedValues: [true, false]
    Default: false

Conditions:
  IsProduction: !Equals [!Ref DeployProd, "true"]

Resources:
  ProdOnlyBucket:
    Type: AWS::S3::Bucket
    Condition: IsProduction
    Properties:
      BucketName: my-prod-only-bucket
Best practices
  • Explicitly set DeletionPolicy for resources you cannot recreate (databases, critical storage).
  • Use Metadata for automation and configuration management, not for critical logic.
  • Prefer intrinsic functions and Conditions rather than heavy DependsOn chains when possible.
  • Refer to the CloudFormation resource type reference for resource-specific optional attributes and nuances.
Further reading and references
Properties are generally required for most resources; Metadata is optional and intended for tooling. DependsOn accepts a single resource name or a list of names. Always consult the resource type reference for the exact required and optional properties for each resource type.

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