AWS CDK Scala

• Overview
• Installation
• Usage
• Limitations
• Acknowledgements

Overview

Scala DSL for AWS CDK v2.

Purpose

• Pass around app & stack scope implicitly.
• Avoid using Java concepts.
  • No builder syntax.
  • Required & optional parameters.
  • ADTs instead of enums.
  • Scala collections (i.e. List & Map).

Disclaimer

This library solely provides a lightweight DSL over the AWS CDK using metaprogramming. Please refer to the underlying types from the AWS CDK along with the associated CloudFormation types for official & up-to-date service documentation.

Scala Support

Version	Supported?
<= 2.11	❌
2.12	✔️
2.13	✔️
3	✔️

Anything <= 2.11 will not be supported. Please do not ask or submit PRs for those versions.

Installation

CDK CLI

You must install v2 of the CDK CLI to synthesize CloudFormation templates.

# Note `@next`, this installs v2.
npm install -g aws-cdk@next

Library

Libraries are published for each AWS service, plus a core library for shared resources. Please refer to the modules directory to reference generated code.

The latest version can be found on mvn and on the releases page.

val cdkVersion: String = ???

libraryDependencies ++= Seq(
  "io.burkard" %% "aws-cdk-scala-core" % cdkVersion,
  "io.burkard" %% "aws-cdk-scala-kinesisanalytics" % cdkVersion,
  "io.burkard" %% "aws-cdk-scala-s3" % cdkVersion
)

Usage

Scala

Create a CDK app within a module of your project.

package io.burkard.cdk.example

import io.burkard.cdk._
import io.burkard.cdk.core._
import io.burkard.cdk.metadata._
import io.burkard.cdk.services.kinesisanalytics._
import io.burkard.cdk.services.s3._

object ExampleApp extends CdkApp {
  CdkStack(id = Some("ExampleStack")) { implicit stackCtx =>
    val envParameter = CfnTypedParameter.CfnStringParameter(
      name = "env",
      allowedValues = Some(List("dev", "qa", "prod"))
    )
    val regionParameter = CfnTypedParameter.CfnStringParameter(
      name = "region",
      allowedValues = Some(List("us-east-1", "us-west-2", "eu-west-1"))
    )

    stackCtx.setCloudFormationInterface(
      CloudFormationInterface.build(
        Some(Label("example parameters")) -> List(envParameter, regionParameter)
      )()
    )

    val env = envParameter.value
    val region = regionParameter.value

    val bucket = Bucket(
      internalResourceId = "Code",
      accessControl = Some(BucketAccessControl.Private),
      enforceSsl = Some(true),
      encryption = Some(BucketEncryption.S3Managed),
      versioned = Some(true)
    )

    CfnApplicationV2(
      internalResourceId = "Runtime",
      serviceExecutionRole = "arn:example-role",
      runtimeEnvironment = "FLINK-1_13",
      tags = Some(
        List(
          CfnTag(key = "env", value = env),
          CfnTag(key = "region", value = region)
        )
      ),
      applicationName = Some(s"prefix-$env-app-name-$region"),
      applicationConfiguration = Some(
        ApplicationConfigurationProperty(
          applicationCodeConfiguration = Some(
            ApplicationCodeConfigurationProperty(
              codeContent = CodeContentProperty(
                s3ContentLocation = Some(
                  S3ContentLocationProperty(
                    fileKey = Some("code-key-in-s3"),
                    bucketArn = Some(bucket.getBucketArn),
                    objectVersion = Some("code-version")
                  )
                )
              ),
              codeContentType = "ZIPFILE"
            )
          )
        )
      )
    )
  }
}

CDK Configuration

Create a cdk.json file at the root of your project, specifying the command to run your CDK app.

{
  "app": "sbt \"example/runMain io.burkard.cdk.example.ExampleApp\""
}

Synthesis

Synthesize the application.

cdk synth

The result is a CloudFormation template in YAML.

Metadata:
  AWS::CloudFormation::Interface:
    ParameterGroups:
      - Label:
          default: example parameters
        Parameters:
          - env
          - region
Parameters:
  env:
    Type: String
    AllowedValues:
      - dev
      - qa
      - prod
    NoEcho: false
  region:
    Type: String
    AllowedValues:
      - us-east-1
      - us-west-2
      - eu-west-1
    NoEcho: false
  BootstrapVersion:
    Type: AWS::SSM::Parameter::Value<String>
    Default: /cdk-bootstrap/hnb659fds/version
    Description: Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]
Resources:
  Code5B760EEF:
    Type: AWS::S3::Bucket
    Properties:
      AccessControl: Private
      BucketEncryption:
        ServerSideEncryptionConfiguration:
          - ServerSideEncryptionByDefault:
              SSEAlgorithm: AES256
      VersioningConfiguration:
        Status: Enabled
    UpdateReplacePolicy: Retain
    DeletionPolicy: Retain
    Metadata:
      aws:cdk:path: ExampleStack/Code/Resource
  CodePolicyAA48735C:
    Type: AWS::S3::BucketPolicy
    Properties:
      Bucket:
        Ref: Code5B760EEF
      PolicyDocument:
        Statement:
          - Action: s3:*
            Condition:
              Bool:
                aws:SecureTransport: "false"
            Effect: Deny
            Principal:
              AWS: "*"
            Resource:
              - Fn::GetAtt:
                  - Code5B760EEF
                  - Arn
              - Fn::Join:
                  - ""
                  - - Fn::GetAtt:
                        - Code5B760EEF
                        - Arn
                    - /*
        Version: "2012-10-17"
    Metadata:
      aws:cdk:path: ExampleStack/Code/Policy/Resource
  Runtime:
    Type: AWS::KinesisAnalyticsV2::Application
    Properties:
      RuntimeEnvironment: FLINK-1_13
      ServiceExecutionRole: arn:example-role
      ApplicationConfiguration:
        ApplicationCodeConfiguration:
          CodeContent:
            S3ContentLocation:
              BucketARN:
                Fn::GetAtt:
                  - Code5B760EEF
                  - Arn
              FileKey: code-key-in-s3
              ObjectVersion: code-version
          CodeContentType: ZIPFILE
      ApplicationName:
        Fn::Join:
          - ""
          - - prefix-
            - Ref: env
            - -app-name-
            - Ref: region
      Tags:
        - Key: env
          Value:
            Ref: env
        - Key: region
          Value:
            Ref: region
    Metadata:
      aws:cdk:path: ExampleStack/Runtime

Limitations

• Builders which use overloading for optional parameters (same name but different types) are represented as paramName0, paramName1, etc..

Acknowledgements

• Inspired by AWS CDK Kotlin DSL.