Table of contents

• Parameters
  • Referencing a Parameter within a Template
  • Parameter Types
  • Pseudo Parameters
    • Available Pseudo Parameters

Parameters

The Parameters section in CloudFormation often comes first in a template.

For more info see the AWS definition here

A Parameter defines an input variable for the template.

Here is an example of a parameter in CloudFormation

Parameters: 
  InstanceTypeParameter: 
    Type: String
    Default: t2.micro
    AllowedValues: 
      - t2.micro
      - m1.small
      - m1.large
    Description: Enter t2.micro, m1.small, or m1.large. Default is t2.micro.

This is what it looks like in KloudFormation

override fun KloudFormation.create() {
    val instanceTypeParameter = parameter<String>(
            logicalName = "InstanceTypeParameter",
            default = "t2.micro",
            allowedValues = listOf("t2.micro", "m1.small", "m1.large"),
            description = "Enter t2.micro, m1.small, or m1.large. Default is t2.micro."
    )
}

Referencing a Parameter within a Template

In CloudFormation you use the Ref Intrinsic function like this

Ec2Instance:
  Type: AWS::EC2::Instance
  Properties:
    InstanceType:
      Ref: InstanceTypeParameter
    ImageId: ami-0ff8a91507f77f867

In KloudFormation you can invoke the ref() function on the parameter.

ref() returns the Reference<T> type which is a Value<T>

instance("Ec2Instance") { 
    instanceType(instanceTypeParameter.ref())
    imageId("ami-0ff8a91507f77f867")
}

Parameter Types

The type property of the parameter takes an instance of ParameterType in the io.kloudformation.model package.

All the AWS Specific Parameter types are provided under the ParameterType class.

val keyName = parameter(
        logicalName = "KeyName",
        description = "Name of an existing EC2 KeyPair to enable SSH access to the instance",
        type = ParameterType.KeyPairNameParameter,
        constraintDescription = "must be the name of an existing EC2 KeyPair."
)
val securityGroupIds = parameter(
        logicalName = "SecurityGroupIds",
        type = ParameterType.SecurityGroupIdListParameter,
        description = "Security groups that can be used to access the EC2 instances",
        constraintDescription = "must be list of EC2 security group ids"
)
val instanceType = parameter<String>(
        logicalName = "InstanceTypeParameter",
        default = "t2.micro",
        allowedValues = listOf("t2.micro", "m1.small", "m1.large"),
        description = "Enter t2.micro, m1.small, or m1.large. Default is t2.micro."
)
instance(logicalName = "EC2Instance") {
    instanceType(instanceType.ref())
    imageId("ami-0ff8a91507f77f867")
    securityGroupIds(securityGroupIds.ref())
    keyName(keyName.ref())
}

Produces the following CloudFormation template

Parameters:
  KeyName:
    Type: "AWS::EC2::KeyPair::KeyName"
    ConstraintDescription: "must be the name of an existing EC2 KeyPair."
    Description: "Name of an existing EC2 KeyPair to enable SSH access to the instance"
  SubnetIds:
    Type: "List<AWS::EC2::SecurityGroup::Id>"
    ConstraintDescription: "must be list of EC2 security group ids"
    Description: "Security groups that can be used to access the EC2 instances"
  InstanceTypeParameter:
    Type: "String"
    AllowedValues:
    - "t2.micro"
    - "m1.small"
    - "m1.large"
    Default: "t2.micro"
    Description: "Enter t2.micro, m1.small, or m1.large. Default is t2.micro."
Resources:
  EC2Instance:
    Type: "AWS::EC2::Instance"
    Properties:
      ImageId: "ami-0ff8a91507f77f867"
      InstanceType:
        Ref: "InstanceTypeParameter"
      KeyName:
        Ref: "KeyName"
      SecurityGroupIds:
        Ref: "SubnetIds"

Pseudo Parameters

All of the AWS Pseudo parameters can be found in io.kloudformation.KloudFormation

For example, in order to output the account id do the following

Info on Pseudo Parameters from AWS can be found here

outputs("StackAccountId" to Output(awsAccountId))

Outputs:
  StackAccountId:
    Value:
      Ref: "AWS::AccountId"

Available Pseudo Parameters

All appear under io.kloudformation.model.KloudFormationTemplate.Builder.Companion

awsAccountId
awsNoValue
awsNotificationArns
awsPartition
awsRegion
awsStackId
awsStackName
awsUrlSuffix