Option 3: Import existing resource into a Nested CloudFormation Stack

How to Import an SNS Topic into a Nested CloudFormation Stack?

When working with AWS CloudFormation, you might find yourself needing to import existing resources into your infrastructure-as-code setup. In this guide, we'll walk through importing an SNS topic into a nested CloudFormation stack.

The Scenario

You have a CloudFormation template with a nested stack structure:

• Main Template (template.yaml): Contains the parent stack that references a nested stack
• Nested Template (nested-templates/sns-stack.yaml): Contains the SNS topic resources.

 

Main template:

AWSTemplateFormatVersion: '2010-09-09'

Transform: AWS::Serverless-2016-10-31

Description: SAM Template with Nested Stacks

Parameters:

Environment:

Type: String

Default: dev

AllowedValues: [dev, staging, prod]

Description: Deployment environment

Resources:

# Parent stack that contains the nested stack

SNSStack:

Type: AWS::CloudFormation::Stack

Properties:

TemplateURL: ./nested-templates/sns-stack.yaml

Parameters:

Environment: !Ref Environment

TopicName: !Sub "MyNotificationTopic-${Environment}"

Outputs:

SNSTopicARN:

Description: The ARN of the SNS topic

Value: !GetAtt SNSStack.Outputs.SNSTopicARN

Export:

Name: !Sub "${AWS::StackName}-SNSTopicARN"

Nested template:

AWSTemplateFormatVersion: '2010-09-09'

Description: Nested Stack for SNS Resources

Parameters:

Environment:

Type: String

Description: Deployment environment

TopicName:

Type: String

Description: Name for the SNS topic

Resources:

SNSTopic:

Type: AWS::SNS::Topic

Properties:

TopicName: !Sub "${TopicName}"

DisplayName: !Sub "Notification Topic for ${Environment}"

Tags:

- Key: Environment

Value: !Ref Environment

Metadata:

SamResourceId: SNSTopic

Outputs:

SNSTopicARN:

Description: The ARN of the SNS topic

Value: !Ref SNSTopic

Export:

Name: !Sub "${AWS::StackName}-SNSTopicARN"

The Challenge: Importing an Existing SNS Topic
You have an existing SNS topic named "invoice" that you want to import into your CloudFormation stack. The topic already exists in your AWS account, and you want to manage it through your infrastructure-as-code.

Step 1: Update the Nested Template
First, add the SNS topic resource to your nested template:

SNSTopicInvoice:

Type: AWS::SNS::Topic

DeletionPolicy: Retain

Properties:

TopicName: invoice

Step 2: Create a Change Set for Import
Use the AWS CLI to create a change set for importing the existing resource. Replace the values of stack-name, template-body, resources to import, TopicArn, etc.

aws cloudformation create-change-set \

--stack-name test-SNSStack-1TN0405IE0OUB \

--change-set-name ImportSNSTopics \

--template-body file:///home/.../migration/nested-templates/sns-stack.yaml \

--change-set-type IMPORT \

--resources-to-import '[{

"ResourceType": "AWS::SNS::Topic",

"LogicalResourceId": "SNSTopicInvoice",

"ResourceIdentifier": {

"TopicArn": "arn:aws:sns:us-east-1:XXX:invoice"

}

}]' \

--parameters \

ParameterKey=Environment,ParameterValue=dev \

ParameterKey=TopicName,ParameterValue=MyNotificationTopic-dev

Step 3: Execute the Change Set
After creating the change set, execute it to perform the import:

aws cloudformation execute-change-set \

--stack-name test-SNSStack-1TN0405IE0OUB \

--change-set-name ImportSNSTopics \

--region us-east-1

 

The resource will be imported, and you can manage it from your IaC. 

alejandro@minipc:~/Documents/delrioworks/migration$ aws cloudformation describe-stack-resources --stack-name test-SNSStack-1TN0405IE0OUB          
{                                                                                                                                                 
    "StackResources": [                                                                                                                           
        {                                                                                                                                         
            "StackName": "test-SNSStack-1TN0405IE0OUB",                                                                                           
            "StackId": "arn:aws:cloudformation:us-east-1:906310767457:stack/test-SNSStack-1TN0405IE0OUB/0de290e0-b42f-11f0-ac84-120e435c95d5",    
            "LogicalResourceId": "SNSTopic",                                                                                                      
            "PhysicalResourceId": "arn:aws:sns:us-east-1:906310767457:MyNotificationTopic-dev",                                                   
            "ResourceType": "AWS::SNS::Topic",                                                                                                    
            "Timestamp": "2025-10-28T18:51:07.484000+00:00",                                                                                      
            "ResourceStatus": "CREATE_COMPLETE",                                                                                                  
            "DriftInformation": {                                                                                                                 
                "StackResourceDriftStatus": "NOT_CHECKED"                                                                                         
            }                                                                                                                                     
        }                                                                                                                                         
    ]                                                                                                                                             
}