Examples of Fn::ForEach in the Resources section - AWS CloudFormation
Replicate an Amazon SNS resourceReplicate an Amazon DynamoDB resourceReplicate multiple resourcesReplicate multiple resources using a nested Fn::ForEach loopsReference replicated properties for an Amazon EC2 resourceReplicate properties for an Amazon EC2 resource

Examples of Fn::ForEach in the Resources section

These examples demonstrate using the Fn::ForEach intrinsic function in the Resources section syntax reference for CloudFormation templates section.

Replicate an Amazon SNS resource

This example snippet returns a list of four Amazon SNS topics, with the logical ID corresponding to the items in the collection (Success, Failure, Timeout, Unknown), with a matching TopicName and FifoTopic set to true.

JSON

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Parameters": {
        "pRepoARNs": {
            "Description": "ARN of SSO instance",
            "Type": "CommaDelimitedList"
        }
    },
    "Resources": {
        "Fn::ForEach::Topics": [
            "TopicName",
            {
                "Ref": "pRepoARNs"
            },
            {
                "SnsTopic${TopicName}": {
                    "Type": "AWS::SNS::Topic",
                    "Properties": {
                        "TopicName": {
                            "Fn::Join": [
                                ".",
                                [
                                    {
                                        "Ref": "TopicName"
                                    },
                                    "fifo"
                                ]
                            ]
                        },
                        "FifoTopic": true
                    }
                }
            }
        ]
    }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Parameters:
  pRepoARNs:
    Description: ARN of SSO instance
    Type: CommaDelimitedList
Resources:
  'Fn::ForEach::Topics':
    - TopicName
    - !Ref pRepoARNs
    - 'SnsTopic${TopicName}':
        Type: 'AWS::SNS::Topic'
        Properties:
          TopicName: 
           'Fn::Join':
            - '.'
            - - !Ref TopicName
              - fifo
          FifoTopic: true

The transformed template will be equivalent to the following template:

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Resources": {
        "SnsTopicSuccess": {
            "Type": "AWS::SNS::Topic",
            "Properties": {
                "TopicName": "Success.fifo",
                "FifoTopic": true
            }
        },
        "SnsTopicFailure": {
            "Type": "AWS::SNS::Topic",
            "Properties": {
                "TopicName": "Failure.fifo",
                "FifoTopic": true
            }
        },
        "SnsTopicTimeout": {
            "Type": "AWS::SNS::Topic",
            "Properties": {
                "TopicName": "Timeout.fifo",
                "FifoTopic": true
            }
        },
        "SnsTopicUnknown": {
            "Type": "AWS::SNS::Topic",
            "Properties": {
                "TopicName": "Unknown.fifo",
                "FifoTopic": true
            }
        }
    }
}

Replicate an Amazon DynamoDB resource

This example snippet creates four AWS::DynamoDB::Table resources with names such as Points, Score, etc.

JSON

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Resources": {
        "Fn::ForEach::Tables": [
            "TableName",
            ["Points", "Score", "Name", "Leaderboard"],
            {
                "DynamoDB${TableName}": {
                    "Type": "AWS::DynamoDB::Table",
                    "Properties": {
                        "TableName": {
                            "Ref": "TableName"
                        },
                        "AttributeDefinitions": [
                            {
                                "AttributeName": "id",
                                "AttributeType": "S"
                            }
                        ],
                        "KeySchema": [
                            {
                                "AttributeName": "id",
                                "KeyType": "HASH"
                            }
                        ],
                        "ProvisionedThroughput": {
                            "ReadCapacityUnits": "5",
                            "WriteCapacityUnits": "5"
                        }
                    }
                }
            }
        ]
    }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Resources:
  'Fn::ForEach::Tables':
    - TableName
    - [Points, Score, Name, Leaderboard]
    - 'DynamoDB${TableName}':
        Type: 'AWS::DynamoDB::Table'
        Properties:
          TableName: !Ref TableName
          AttributeDefinitions:
            - AttributeName: id
              AttributeType: S
          KeySchema:
            - AttributeName: id
              KeyType: HASH
          ProvisionedThroughput:
            ReadCapacityUnits: '5'
            WriteCapacityUnits: '5'

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Resources:
  DynamoDBPoints:
    Type: 'AWS::DynamoDB::Table'
    Properties:
      TableName: Points
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'
  DynamoDBScore:
    Type: 'AWS::DynamoDB::Table'
    Properties:
      TableName: Score
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'
  DynamoDBName:
    Type: 'AWS::DynamoDB::Table'
    Properties:
      TableName: Name
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'
  DynamoDBLeaderboard:
    Type: 'AWS::DynamoDB::Table'
    Properties:
      TableName: Leaderboard
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'

Replicate multiple resources

This example creates multiple instances of AWS::EC2::NatGateway and AWS::EC2::EIP using a naming convention of "{ResourceType}${Identifier}". You can declare multiple resource types under one Fn::ForEach loop to take advantage of a single identifier.

Note

The example below assumes the TwoNatGateways and ThreeNatGateways Conditions exist, and PublicSubnetA, PublicSubnetB, and PublicSubnetC Resources are defined.

Note

Unique values for each element in the Collection are defined within the Mappings section, where the Fn::FindInMap intrinsic function is used to reference the corresponding value. If Fn::FindInMap is unable to find the corresponding identifier, the Condition property will not be set resolving to !Ref ‘AWS:::NoValue.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Mappings": {
    "NatGateway": {
      "Condition": {
        "B": "TwoNatGateways",
        "C": "ThreeNatGateways"
      }
    }
  },
  "Resources": {
    "Fn::ForEach::NatGatewayAndEIP": [
      "Identifier",
      [ "A", "B", "C" ],
      {
        "NatGateway${Identifier}": {
          "Type": "AWS::EC2::NatGateway",
          "Properties": {
            "AllocationId": {
              "Fn::GetAtt": [
                {
                  "Fn::Sub": "NatGatewayAttachment${Identifier}"
                },
                "AllocationId"
              ]
            },
            "SubnetId": {
              "Ref": {
                "Fn::Sub": "PublicSubnet${Identifier}"
              }
            }
          },
          "Condition": {
            "Fn::FindInMap": [
              "NatGateway",
              "Condition",
              {
                "Ref": "Identifier"
              },
              {
                "DefaultValue": {
                  "Ref": "AWS::NoValue"
                }
              }
            ]
          }
        },
        "NatGatewayAttachment${Identifier}": {
          "Type": "AWS::EC2::EIP",
          "Properties": {
            "Domain": "vpc"
          },
          "Condition": {
            "Fn::FindInMap": [
              "NatGateway",
              "Condition",
              {
                "Ref": "Identifier"
              },
              {
                "DefaultValue": {
                  "Ref": "AWS::NoValue"
                }
              }
            ]
          }
        }
      }
    ]
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Mappings:
  NatGateway:
    Condition:
      B: TwoNatGateways
      C: ThreeNatGateways
Resources:
  Fn::ForEach::NatGatewayAndEIP:
    - Identifier
    - - A
      - B
      - C
    - NatGateway${Identifier}:
        Type: AWS::EC2::NatGateway
        Properties:
          AllocationId: !GetAtt
            - !Sub NatGatewayAttachment${Identifier}
            - AllocationId
          SubnetId: !Ref
            Fn::Sub: PublicSubnet${Identifier}
        Condition: !FindInMap
          - NatGateway
          - Condition
          - !Ref Identifier
          - DefaultValue: !Ref AWS::NoValue
      NatGatewayAttachment${Identifier}:
        Type: AWS::EC2::EIP
        Properties:
          Domain: vpc
        Condition: !FindInMap
          - NatGateway
          - Condition
          - !Ref Identifier
          - DefaultValue: !Ref AWS::NoValue

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  NatGatewayA:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt
        - NatGatewayAttachmentA
        - AllocationId
      SubnetId: !Ref PublicSubnetA
  NatGatewayB:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt
        - NatGatewayAttachmentB
        - AllocationId
      SubnetId: !Ref PublicSubnetB
    Condition: TwoNatGateways
  NatGatewayC:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt
        - NatGatewayAttachmentC
        - AllocationId
      SubnetId: !Ref PublicSubnetC
    Condition: ThreeNatGateways
  NatGatewayAttachmentA:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
  NatGatewayAttachmentB:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
    Condition: TwoNatGateways
  NatGatewayAttachmentC:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
    Condition: ThreeNatGateways

Replicate multiple resources using a nested Fn::ForEach loops

This example uses nested Fn::ForEach loops to map three resources ( AWS::EC2::NetworkAcl, AWS::EC2::Subnet, and AWS::EC2::SubnetNetworkAclAssociation) with each other.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Resources": {
    "VPC": {
      "Type": "AWS::EC2::VPC",
      "Properties": {
        "CidrBlock": "10.0.0.0/16",
        "EnableDnsSupport": "true",
        "EnableDnsHostnames": "true"
      }
    },
    "Fn::ForEach::SubnetResources": [
      "Prefix",
      [
        "Transit",
        "Public"
      ],
      {
        "Nacl${Prefix}Subnet": {
          "Type": "AWS::EC2::NetworkAcl",
          "Properties": {
            "VpcId": {
              "Ref": "VPC"
            }
          }
        },
        "Fn::ForEach::LoopInner": [
          "Suffix",
          [
            "A",
            "B",
            "C"
          ],
          {
            "${Prefix}Subnet${Suffix}": {
              "Type": "AWS::EC2::Subnet",
              "Properties": {
                "VpcId": {
                  "Ref": "VPC"
                }
              }
            },
            "Nacl${Prefix}Subnet${Suffix}Association": {
              "Type": "AWS::EC2::SubnetNetworkAclAssociation",
              "Properties": {
                "SubnetId": {
                  "Ref": {
                    "Fn::Sub": "${Prefix}Subnet${Suffix}"
                  }
                },
                "NetworkAclId": {
                  "Ref": {
                    "Fn::Sub": "Nacl${Prefix}Subnet"
                  }
                }
              }
            }
          }
        ]
      }
    ]
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Resources:
  VPC:
    Type: 'AWS::EC2::VPC'
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
  'Fn::ForEach::SubnetResources':
  - Prefix
  - [Transit, Public]
  - 'Nacl${Prefix}Subnet':
      Type: 'AWS::EC2::NetworkAcl'
      Properties:
        VpcId: !Ref 'VPC'
    'Fn::ForEach::LoopInner':
    - Suffix
    - [A, B, C]
    - '${Prefix}Subnet${Suffix}':
        Type: 'AWS::EC2::Subnet'
        Properties:
          VpcId: !Ref 'VPC'
      'Nacl${Prefix}Subnet${Suffix}Association':
        Type: 'AWS::EC2::SubnetNetworkAclAssociation'
        Properties:
          SubnetId: !Ref
            'Fn::Sub': '${Prefix}Subnet${Suffix}'
          NetworkAclId: !Ref
            'Fn::Sub': 'Nacl${Prefix}Subnet'

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Resources:
  VPC:
    Type: 'AWS::EC2::VPC'
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
  NaclTransitSubnet:
    Type: 'AWS::EC2::NetworkAcl'
    Properties:
      VpcId: !Ref VPC
  TransitSubnetA:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref VPC
  NaclTransitSubnetAAssociation:
    Type: 'AWS::EC2::SubnetNetworkAclAssociation'
    Properties:
      SubnetId: !Ref TransitSubnetA
      NetworkAclId: !Ref NaclTransitSubnet
  TransitSubnetB:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref VPC
  NaclTransitSubnetBAssociation:
    Type: 'AWS::EC2::SubnetNetworkAclAssociation'
    Properties:
      SubnetId: !Ref TransitSubnetB
      NetworkAclId: !Ref NaclTransitSubnet
  TransitSubnetC:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref VPC
  NaclTransitSubnetCAssociation:
    Type: 'AWS::EC2::SubnetNetworkAclAssociation'
    Properties:
      SubnetId: !Ref TransitSubnetC
      NetworkAclId: !Ref NaclTransitSubnet
  NaclPublicSubnet:
    Type: 'AWS::EC2::NetworkAcl'
    Properties:
      VpcId: !Ref VPC
  PublicSubnetA:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref VPC
  NaclPublicSubnetAAssociation:
    Type: 'AWS::EC2::SubnetNetworkAclAssociation'
    Properties:
      SubnetId: !Ref PublicSubnetA
      NetworkAclId: !Ref NaclPublicSubnet
  PublicSubnetB:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref VPC
  NaclPublicSubnetBAssociation:
    Type: 'AWS::EC2::SubnetNetworkAclAssociation'
    Properties:
      SubnetId: !Ref PublicSubnetB
      NetworkAclId: !Ref NaclPublicSubnet
  PublicSubnetC:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref VPC
  NaclPublicSubnetCAssociation:
    Type: 'AWS::EC2::SubnetNetworkAclAssociation'
    Properties:
      SubnetId: !Ref PublicSubnetC
      NetworkAclId: !Ref NaclPublicSubnet

Reference replicated properties for an Amazon EC2 resource

This example uses the Fn::ForEach intrinsic function to reference replicated AWS::EC2::Instance resources.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Mappings": {
    "Instances": {
      "InstanceType": {
        "B": "m5.4xlarge",
        "C": "c5.2xlarge"
      },
      "ImageId": {"A": "ami-id1"}
    }
  },
  "Resources": {
    "Fn::ForEach::Instances": [
      "Identifier",
      [
        "A",
        "B",
        "C"
      ],
      {
        "Instance${Identifier}": {
          "Type": "AWS::EC2::Instance",
          "Properties": {
            "InstanceType": {
              "Fn::FindInMap": [
                "Instances",
                "InstanceType",
                {"Ref": "Identifier"},
                {"DefaultValue": "m5.xlarge"}
              ]
            },
            "ImageId": {
              "Fn::FindInMap": [
                "Instances",
                "ImageId",
                {"Ref": "Identifier"},
                {"DefaultValue": "ami-id-default"}
              ]
            }
          }
        }
      }
    ]
  },
  "Outputs": {
    "SecondInstanceId": {
      "Description": "Instance Id for InstanceB",
      "Value": {"Ref": "InstanceB"}
    },
    "SecondPrivateIp": {
      "Description": "Private IP for InstanceB",
      "Value": {
        "Fn::GetAtt": [
          "InstanceB",
          "PrivateIp"
        ]
      }
    }
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Mappings:
  Instances:
    InstanceType:
      B: m5.4xlarge
      C: c5.2xlarge
    ImageId:
      A: ami-id1
Resources:
  'Fn::ForEach::Instances':
  - Identifier
  - [A, B, C]
  - 'Instance${Identifier}':
      Type: 'AWS::EC2::Instance'
      Properties:
        InstanceType: !FindInMap [Instances, InstanceType, !Ref 'Identifier', {DefaultValue: m5.xlarge}]
        ImageId: !FindInMap [Instances, ImageId, !Ref 'Identifier', {DefaultValue: ami-id-default}]
Outputs:
  SecondInstanceId:
    Description: Instance Id for InstanceB
    Value: !Ref 'InstanceB'
  SecondPrivateIp:
    Description: Private IP for InstanceB
    Value: !GetAtt [InstanceB, PrivateIp]

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Resources:
  InstanceA:
    Type: 'AWS::EC2::Instance'
    Properties:
      InstanceType: m5.xlarge
      ImageId: ami-id1
  InstanceB:
    Type: 'AWS::EC2::Instance'
    Properties:
      InstanceType: m5.4xlarge
      ImageId: ami-id-default
  InstanceC:
    Type: 'AWS::EC2::Instance'
    Properties:
      InstanceType: c5.2xlarge
      ImageId: ami-id-default
Outputs:
  SecondInstanceId:
    Description: Instance Id for InstanceB
    Value: !Ref InstanceB
  SecondPrivateIp:
    Description: Private IP for InstanceB
    Value: !GetAtt [InstanceB, PrivateIp]

Replicate properties for an Amazon EC2 resource

This example uses the Fn::ForEach intrinsic function to repeat some properties like ImageId, InstanceType, and AvailabilityZone to an AWS::EC2::Instance resource.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Mappings": {
    "InstanceA": {
      "Properties": {
        "ImageId": "ami-id1",
        "InstanceType": "m5.xlarge"
      }
    },
    "InstanceB": {
      "Properties": {
        "ImageId": "ami-id2"
      }
    },
    "InstanceC": {
      "Properties": {
        "ImageId": "ami-id3",
        "InstanceType": "m5.2xlarge",
        "AvailabilityZone": "us-east-1a"
      }
    }
  },
  "Resources": {
    "Fn::ForEach::Instances": [
      "InstanceLogicalId",
      [ "InstanceA", "InstanceB", "InstanceC" ],
      {
        "${InstanceLogicalId}": {
          "Type": "AWS::EC2::Instance",
          "Properties": {
            "DisableApiTermination": true,
            "UserData": {
              "Fn::Base64": {
                "Fn::Join": [
                  "",
                  [
                    "#!/bin/bash\n",
                    "yum update -y\n",
                    "yum install -y httpd.x86_64\n",
                    "systemctl start httpd.service\n",
                    "systemctl enable httpd.service\n",
                    "echo \"Hello World from $(hostname -f)\" > /var/www/html/index.html\n"
                  ]
                ]
              }
            },
            "Fn::ForEach::Properties": [
              "PropertyName",
              [ "ImageId", "InstanceType", "AvailabilityZone" ],
              {
                "${PropertyName}": {
                  "Fn::FindInMap": [
                    { "Ref": "InstanceLogicalId" },
                    "Properties",
                    { "Ref": "PropertyName"},
                    {
                      "DefaultValue": { "Ref": "AWS::NoValue" }
                    }
                  ]
                }
              }
            ]
          }
        }
      }
    ]
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Mappings:
  InstanceA:
    Properties:
      ImageId: ami-id1
      InstanceType: m5.xlarge
  InstanceB:
    Properties:
      ImageId: ami-id2
  InstanceC:
    Properties:
      ImageId: ami-id3
      InstanceType: m5.2xlarge
      AvailabilityZone: us-east-1a
Resources:
  'Fn::ForEach::Instances':
  - InstanceLogicalId
  - [InstanceA, InstanceB, InstanceC]
  - '${InstanceLogicalId}':
      Type: 'AWS::EC2::Instance'
      Properties:
        DisableApiTermination: true
        UserData:
          Fn::Base64: !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
        'Fn::ForEach::Properties':
          - PropertyName
          - [ImageId, InstanceType, AvailabilityZone]
          - '${PropertyName}':
             'Fn::FindInMap':
               - Ref: 'InstanceLogicalId'
               - Properties
               - Ref: 'PropertyName'
               - {DefaultValue: !Ref 'AWS::NoValue'}

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: 'AWS::LanguageExtensions'
Resources:
  InstanceA:
    Type: 'AWS::EC2::Instance'
    Properties:
      DisableApiTermination: true
      UserData:
        Fn::Base64: 
          !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
      ImageId: ami-id1
      InstanceType: m5.xlarge
  InstanceB:
    Type: 'AWS::EC2::Instance'
    Properties:
      DisableApiTermination: true
      UserData:
        Fn::Base64: 
          !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
      ImageId: ami-id2
  InstanceC:
    Type: 'AWS::EC2::Instance'
    Properties:
      DisableApiTermination: true
      UserData:
        Fn::Base64: 
          !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
      ImageId: ami-id3
      InstanceType: m5.2xlarge
      AvailabilityZone: us-east-1a