cdk8s-aws-cdk

AWS CDK Adapter for cdk8s allows you to define AWS CDK constructs within a cdk8s application. The AWS resources will be provisioned using the AWS Controllers for Kubernetes.

DO NOT USE THIS IN PRODUCTION

This project is in very early alpha stages of development and is subject to frequent breaking changes.

Pre-requisites

In you Kubernetes cluster, install the appropriate ACK controllers, depending on which resources you want to provision.

Getting Started

Install the adapter and the AWS CDK in your cdk8s project.

npm install cdk8s-aws-cdk aws-cdk-lib

The adapter provides a special Chart, that allows defining AWS CDK resources. You must extend this chart, in place of the normal cdk8s.Chart object.

import * as awscdkadapter from 'cdk8s-aws-cdk'
import * as k from 'cdk8s';
import * as kplus from 'cdk8s-plus-24';
import { aws_s3 as s3 } from 'aws-cdk-lib';

export class MyChart extends awscdkadapter.Chart {

  constructor(scope: Construct, id: string, props: k.ChartProps = {}) {
    super(scope, id, props);

    // define an s3 bucket with aws-cdk
    new s3.Bucket(this, 'Bucket');

    // define a kubernetes deployment with cdk8s+
    new kplus.Deployment(this, 'Deployment', {
      containers: [{ image: 'image' }],
    });

  }

}

Synthesizing this chart will produce:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: s3sample-deployment-c828e7a5
spec:
  minReadySeconds: 0
  progressDeadlineSeconds: 600
  replicas: 1
  selector:
    matchLabels:
      cdk8s.io/metadata.addr: S3Sample-Deployment-c8c2c08d
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      labels:
        cdk8s.io/metadata.addr: S3Sample-Deployment-c8c2c08d
    spec:
      automountServiceAccountToken: true
      containers:
        - image: image
          imagePullPolicy: Always
          name: main
          securityContext:
            privileged: false
            readOnlyRootFilesystem: false
            runAsNonRoot: false
      dnsPolicy: ClusterFirst
      securityContext:
        fsGroupChangePolicy: Always
        runAsNonRoot: false
      setHostnameAsFQDN: false
---
apiVersion: s3.services.k8s.aws/v1alpha1
kind: Bucket
metadata:
  name: s3sample-bucket83908e77-c80d1127
spec:
  name: s3sample-bucket83908e77-c80d1127

You can then apply this manifest to the cluster by any means.

Limitations

The are quite a few limitations at the moment.

Resource Coverage

There are two layers of resource coverage that are involved in the process:

ACK Resources

The adapter maps every AWS CDK resource to its corresponding ACK resource. This means resources that aren't currently supported by ACK cannot be defined.

Adapter Mappers

For resources that are supported by ACK, this adapter contains mappers that can do the translation. Not all supported resources have been mapped yet, the built-in mapped resources are:

• EC2 Security Group
• IAM Policy
• IAM Role
• Lambda Function
• RDS DB Instance
• RDS Subnet Group
• S3 Bucket

If your application contains additional resources, that are supported by ACK but haven't been mapped by the adapter, you can register customer mappers:

First you implement a custom mapper:

import * as awscdkadapter from 'cdk8s-aws-cdk'

export class KmsKeyMapper extends awscdkadapter.CloudFormationResourceMapper {

  /**
   * @see CloudFormationResourceMapper.type
   */
  public readonly type: string = 'AWS::KMS::Key';

  // implement the additional required methods and properties
  ...
}

Then you register it:

import * as awscdkadapter from 'cdk8s-aws-cdk'
import * as k from 'cdk8s';
import { aws_kms as kms } from 'aws-cdk-lib';

export class MyChart extends awscdkadapter.Chart {

  constructor(scope: Construct, id: string, props: k.ChartProps = {}) {
    super(scope, id, props);

    this.registerMapper(new KmsKeyMapper(this))

    // now you can define a kms key
    new kms.Key(this, 'Key');

  }

}

Attributes

CDK Tokens that represent CloudFormation attributes (i.e Fn::GetAttr) can be used as Kubernetes environment variables when defining containers, but they cannot be used for anything else.

For example, you can pass an attribute to a container like so:

const dbInstance = new rds.DatabaseInstance(...);
const container = deployment.addContainer(...);

container.env.addVariable('DB_ADDRESS', kplus.EnvValue.fromValue(dbInstance.dbInstanceEndpointAddress))

But you cannot pass the same attribute to, for example, lambda function environment variables:

const dbInstance = new rds.DatabaseInstance(...);
const func = new lambda.Function(...);

func.addEnvironment('DB_ADDRESS', dbInstance.dbInstanceEndpointAddress);

This is because attribute mapping is implemented by exporting them using ACK Field Exports. These field exports can only be imported in a select number of resources, and currently the adapter only supports kubernetes environment variables.

Assets

AWS CDK assets are currently not supported.

Examples

• Kubernetes deployment that writes to an RDS PostgreSQL database.