Fn::ImportValue - AWS CloudFormation (original) (raw)

The intrinsic function Fn::ImportValue returns the value of an output exported by another stack. You typically use this function to create cross-stack references. In the following example template snippets, Stack A exports VPC security group values and Stack B imports them.

Note

The following restrictions apply to cross-stack references:

• For each AWS account, Export names must be unique within a Region.
• You can't create cross-stack references across Regions. You can use the intrinsic functionFn::ImportValue to import only values that have been exported within the same Region.
• For outputs, the value of the Name property of an Export can't use Ref or GetAtt functions that depend on a resource.
  Similarly, the ImportValue function can't include Ref or GetAtt functions that depend on a resource.
• After another stack imports an output value, you can't delete the stack that is exporting the output value or modify the exported output value. All the imports must be removed before you can delete the exporting stack or modify the output value.

JSON

Stack A Export

"Outputs" : {
  "PublicSubnet" : {
    "Description" : "The subnet ID to use for public web servers",
    "Value" :  { "Ref" : "PublicSubnet" },
    "Export" : { "Name" : {"Fn::Sub": "${AWS::StackName}-SubnetID" }}
  },
  "WebServerSecurityGroup" : {
    "Description" : "The security group ID to use for public web servers",
    "Value" :  { "Fn::GetAtt" : ["WebServerSecurityGroup", "GroupId"] },
    "Export" : { "Name" : {"Fn::Sub": "${AWS::StackName}-SecurityGroupID" }}
  }
}

YAML

Stack A Export

Outputs:
  PublicSubnet:
    Description: The subnet ID to use for public web servers
    Value:
      Ref: PublicSubnet
    Export:
      Name:
        'Fn::Sub': '${AWS::StackName}-SubnetID'
  WebServerSecurityGroup:
    Description: The security group ID to use for public web servers
    Value:
      'Fn::GetAtt':
        - WebServerSecurityGroup
        - GroupId
    Export:
      Name:
        'Fn::Sub': '${AWS::StackName}-SecurityGroupID'

JSON

Stack B Import

"Resources" : {
  "WebServerInstance" : {
    "Type" : "AWS::EC2::Instance",
    "Properties" : {
      "InstanceType" : "t2.micro",
      "ImageId" : "ami-a1b23456",
      "NetworkInterfaces" : [{
        "GroupSet" : [{"Fn::ImportValue" : {"Fn::Sub" : "${NetworkStackNameParameter}-SecurityGroupID"}}],
        "AssociatePublicIpAddress" : "true",
        "DeviceIndex" : "0",
        "DeleteOnTermination" : "true",
        "SubnetId" : {"Fn::ImportValue" : {"Fn::Sub" : "${NetworkStackNameParameter}-SubnetID"}}
      }]
    }
  }
}

YAML

Stack B Import

Resources:
  WebServerInstance:
    Type: 'AWS::EC2::Instance'
    Properties:
      InstanceType: t2.micro
      ImageId: ami-a1b23456
      NetworkInterfaces:
        - GroupSet:
            - Fn::ImportValue: 
              'Fn::Sub': '${NetworkStackNameParameter}-SecurityGroupID'
          AssociatePublicIpAddress: 'true'
          DeviceIndex: '0'
          DeleteOnTermination: 'true'
          SubnetId: Fn::ImportValue: 
            'Fn::Sub': '${NetworkStackNameParameter}-SubnetID'

Declaration

JSON

{ "Fn::ImportValue" : sharedValueToImport }

YAML

You can use the full function name:

Fn::ImportValue: sharedValueToImport

Alternatively, you can use the short form:

!ImportValue sharedValueToImport

Important

You can't use the short form of !ImportValue when it contains the short form of!Sub.

# do not use
!ImportValue
  !Sub '${NetworkStack}-SubnetID' 

Instead, you must use the full function name, for example:

Fn::ImportValue:
  !Sub "${NetworkStack}-SubnetID"

Parameters

sharedValueToImport

The stack output value that you want to import.

Return value

The stack output value.

Example

JSON

{ "Fn::ImportValue" : {"Fn::Sub": "${NetworkStackNameParameter}-SubnetID" } }

YAML

Fn::ImportValue:
  !Sub "${NetworkStackName}-SecurityGroupID"

Supported functions

You can use the following functions in the Fn::ImportValue function. The value of these functions can't depend on a resource.

• Fn::Base64
• Fn::FindInMap
• Fn::If
• Fn::Join
• Fn::Select
• Fn::Sub
• Ref