CloudFormation template Mappings syntax - AWS CloudFormation
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CloudFormation template Mappings syntax

The optional Mappings section helps you create key-value pairs that can be used to specify values based on certain conditions or dependencies.

One common use case for the Mappings section is to set values based on the AWS Region where the stack is deployed. This can be achieved by using the AWS::Region pseudo parameter. The AWS::Region pseudo parameter is a value that CloudFormation resolves to the region where the stack is created. Pseudo parameters are resolved by CloudFormation when you create the stack.

To retrieve values in a map, you can use the Fn::FindInMap intrinsic function within the Resources section of your template.

Syntax

The Mappings section uses the following syntax:

JSON

"Mappings" : { "MappingLogicalName" : { "Key1" : { "Name" : "Value1" }, "Key2" : { "Name" : "Value2" }, "Key3" : { "Name" : "Value3" } } }

YAML

Mappings: MappingLogicalName: Key1: Name: Value1 Key2: Name: Value2 Key3: Name: Value3

  • MappingLogicalName is the logical name for the mapping.

  • Within the mapping, each map is a key followed by another mapping.

  • The key must be a map of name-value pairs and unique within the mapping.

  • The name-value pair is a label, and the value to map. By naming the values, you can map more than one set of values to a key.

  • The keys in mappings must be literal strings.

  • The values can be of type String or List.

Note

You can't include parameters, pseudo parameters, or intrinsic functions in the Mappings section.

If the values in a mapping aren't currently used by your stack, you cannot update the mapping alone. You must include changes that add, modify, or delete resources.

Examples

Basic mapping

The following example shows a Mappings section with a map RegionToInstanceType, which contains five keys that map to name-value pairs containing single string values. The keys are region names. Each name-value pair is an instance type from the T family that's available in the region represented by the key. The name-value pairs have a name (InstanceType in the example) and a value.

JSON

"Mappings" : { "RegionToInstanceType" : { "us-east-1" : { "InstanceType" : "t2.micro" }, "us-west-1" : { "InstanceType" : "t2.micro" }, "eu-west-1" : { "InstanceType" : "t2.micro" }, "eu-north-1" : { "InstanceType" : "t3.micro" }, "me-south-1" : { "InstanceType" : "t3.micro" } } }

YAML

Mappings: RegionToInstanceType: us-east-1: InstanceType: t2.micro us-west-1: InstanceType: t2.micro eu-west-1: InstanceType: t2.micro eu-north-1: InstanceType: t3.micro me-south-1: InstanceType: t3.micro

Mapping with multiple values

The following example has region keys that are mapped to two sets of values: one named MyAMI1 and the other MyAMI2.

Note

The AMI IDs shown in these examples are placeholders for demonstration purposes. Whenever possible, consider using dynamic references to AWS Systems Manager parameters as an alternative to the Mappings section. To avoid updating all your templates with a new ID each time the AMI that you want to use changes, use a AWS Systems Manager parameter to retrieve the latest AMI ID when the stack is created or updated. The latest versions of commonly used AMIs are also available as public parameters in Systems Manager. For more information, see Get values stored in other services using dynamic references.

JSON

"Mappings" : { "RegionToAMI" : { "us-east-1" : { "MyAMI1" : "ami-12345678901234567", "MyAMI2" : "ami-23456789012345678" }, "us-west-1" : { "MyAMI1" : "ami-34567890123456789", "MyAMI2" : "ami-45678901234567890" }, "eu-west-1" : { "MyAMI1" : "ami-56789012345678901", "MyAMI2" : "ami-67890123456789012" }, "ap-southeast-1" : { "MyAMI1" : "ami-78901234567890123", "MyAMI2" : "ami-89012345678901234" }, "ap-northeast-1" : { "MyAMI1" : "ami-90123456789012345", "MyAMI2" : "ami-01234567890123456" } } }

YAML

Mappings: RegionToAMI: us-east-1: MyAMI1: ami-12345678901234567 MyAMI2: ami-23456789012345678 us-west-1: MyAMI1: ami-34567890123456789 MyAMI2: ami-45678901234567890 eu-west-1: MyAMI1: ami-56789012345678901 MyAMI2: ami-67890123456789012 ap-southeast-1: MyAMI1: ami-78901234567890123 MyAMI2: ami-89012345678901234 ap-northeast-1: MyAMI1: ami-90123456789012345 MyAMI2: ami-01234567890123456

Return a value from a mapping

You can use the Fn::FindInMap function to return a named value based on a specified key. The following example template contains an Amazon EC2 resource whose InstanceType property is assigned by the FindInMap function. The FindInMap function specifies key as the AWS Region where the stack is created (using the AWS::Region pseudo parameter) and InstanceType as the name of the value to map to. The ImageId uses a Systems Manager parameter to dynamically retrieve the latest Amazon Linux 2 AMI. For more information about pseudo parameters, see Get AWS values using pseudo parameters.

JSON

{ "AWSTemplateFormatVersion" : "2010-09-09", "Mappings" : { "RegionToInstanceType" : { "us-east-1" : { "InstanceType" : "t2.micro" }, "us-west-1" : { "InstanceType" : "t2.micro" }, "eu-west-1" : { "InstanceType" : "t2.micro" }, "eu-north-1" : { "InstanceType" : "t3.micro" }, "me-south-1" : { "InstanceType" : "t3.micro" } } }, "Resources" : { "myEC2Instance" : { "Type" : "AWS::EC2::Instance", "Properties" : { "ImageId" : "{{resolve:ssm:/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2}}", "InstanceType" : { "Fn::FindInMap" : [ "RegionToInstanceType", { "Ref" : "AWS::Region" }, "InstanceType" ]} } } } }

YAML

AWSTemplateFormatVersion: 2010-09-09 Mappings: RegionToInstanceType: us-east-1: InstanceType: t2.micro us-west-1: InstanceType: t2.micro eu-west-1: InstanceType: t2.micro eu-north-1: InstanceType: t3.micro me-south-1: InstanceType: t3.micro Resources: myEC2Instance: Type: AWS::EC2::Instance Properties: ImageId: '{{resolve:ssm:/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2}}' InstanceType: !FindInMap [RegionToInstanceType, !Ref 'AWS::Region', InstanceType]

Input parameter and Fn::FindInMap

The following example template shows how to create an EC2 instance using multiple mappings. The template uses nested mappings to automatically select the appropriate instance type and security group based on the target AWS Region and environment type (Dev or Prod). It also uses a Systems Manager parameter to dynamically retrieve the latest Amazon Linux 2 AMI.

JSON

{ "AWSTemplateFormatVersion" : "2010-09-09", "Parameters" : { "EnvironmentType" : { "Description" : "The environment type (Dev or Prod)", "Type" : "String", "Default" : "Dev", "AllowedValues" : [ "Dev", "Prod" ] } }, "Mappings" : { "RegionAndEnvironmentToInstanceType" : { "us-east-1" : { "Dev" : "t3.micro", "Prod" : "c5.large" }, "us-west-1" : { "Dev" : "t2.micro", "Prod" : "m5.large" } }, "RegionAndEnvironmentToSecurityGroup" : { "us-east-1" : { "Dev" : "sg-12345678", "Prod" : "sg-abcdef01" }, "us-west-1" : { "Dev" : "sg-ghijkl23", "Prod" : "sg-45678abc" } } }, "Resources" : { "Ec2Instance" : { "Type" : "AWS::EC2::Instance", "Properties" : { "ImageId" : "{{resolve:ssm:/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2}}", "InstanceType" : { "Fn::FindInMap": [ "RegionAndEnvironmentToInstanceType", { "Ref": "AWS::Region" }, { "Ref": "EnvironmentType" } ]}, "SecurityGroupIds" : [{ "Fn::FindInMap" : [ "RegionAndEnvironmentToSecurityGroup", { "Ref" : "AWS::Region" }, { "Ref" : "EnvironmentType" } ]}] } } } }

YAML

AWSTemplateFormatVersion: 2010-09-09 Parameters: EnvironmentType: Description: The environment type (Dev or Prod) Type: String Default: Dev AllowedValues: - Dev - Prod Mappings: RegionAndEnvironmentToInstanceType: us-east-1: Dev: t3.micro Prod: c5.large us-west-1: Dev: t2.micro Prod: m5.large RegionAndEnvironmentToSecurityGroup: us-east-1: Dev: sg-12345678 Prod: sg-abcdef01 us-west-1: Dev: sg-ghijkl23 Prod: sg-45678abc Resources: Ec2Instance: Type: AWS::EC2::Instance Properties: ImageId: '{{resolve:ssm:/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2}}' InstanceType: !FindInMap [RegionAndEnvironmentToInstanceType, !Ref 'AWS::Region', !Ref EnvironmentType] SecurityGroupIds: - !FindInMap [RegionAndEnvironmentToSecurityGroup, !Ref 'AWS::Region', !Ref EnvironmentType]

These related topics can be helpful as you develop templates that use the Fn::FindInMap function.