Use CDK8S To Create AWS Controllers for Kubernetes Custom Resources

Abstract

There is a question, How does ACK relate to cdk8s?
Answer: All of the ACK controllers watch for specific CRs and you can generate those resources using cdk8s. The two projects complement each other. cdk8s can create the Kubernetes resources and ACK uses those resources to create the AWS infrastructure.
This post gives an example of generating Kubernetes manifest of ACK using cdk8s typescript

Pre-requisite
Init cdk8s-app projen
Import ACK CRDS As CDK8S API
Get your hands dirty with code now
Build manifest
Conclusion

🚀 Pre-requisite

This post expects you to know ACK and cdk8s.
You can base on the AWS Controllers for Kubernetes Hands-on to test the generated manifests by cdk8s
projen is a plus

🚀 Init cdk8s-app projen

You can just init cdk8s project using cdk8s init typescript-app but the following is used projen to manage configuration through code

Init cdk8s-app-ts with projen in typescript.

  ⚡ $ projen new cdk8s-app-ts --projenrc-ts

cdk8s import

  ⚡ $ cdk8s import --language typescript --output src/imports
  Importing k8s v1.22.0...
  Importing resources, this may take a few moments...
  k8s

🚀 Import ACK CRDS As CDK8S API

s3-controller crds

  ⚡ $ cdk8s import https://raw.githubusercontent.com/aws-controllers-k8s/s3-controller/main/helm/crds/s3.services.k8s.aws_buckets.yaml --output src/imports/
  Importing resources, this may take a few moments...
  s3.services.k8s.aws
    s3.services.k8s.aws/bucket

rds-controller crds, rename the file from rds.services.k8s.aws.ts to rds.services.db.instance.k8s.aws.ts after import due to that name is assigned for all CRDS within the rds-controller crds

  ⚡ $ cdk8s import https://raw.githubusercontent.com/aws-controllers-k8s/rds-controller/main/helm/crds/rds.services.k8s.aws_dbinstances.yaml --output src/imports/
  Importing resources, this may take a few moments...
  rds.services.k8s.aws
    rds.services.k8s.aws/dbinstance

  ⚡ $ mv src/imports/rds.services.k8s.aws.ts src/imports/rds.services.db.instance.k8s.aws.ts

RDS subnet group, rename the file from rds.services.k8s.aws.ts to rds.services.subnet.group.k8s.aws.ts

  ⚡ $ cdk8s import https://raw.githubusercontent.com/aws-controllers-k8s/rds-controller/main/helm/crds/rds.services.k8s.aws_dbsubnetgroups.yaml --output src/imports/
  Importing resources, this may take a few moments...
  rds.services.k8s.aws
    rds.services.k8s.aws/dbsubnetgroup

  ⚡ $ mv src/imports/rds.services.k8s.aws.ts src/imports/rds.services.subnet.group.k8s.aws.ts

🚀 Get your hands dirty with code now

RDS
```
  rds
  ├── constants.ts
  ├── db-instance.ts
  └── subnet-group.ts
```
- DBInstance requires a subnet group which contains private subnets in EKS VPC (subnet-group.ts) and secret keys to hold user credentials. The k8s secret is not generated through code here.
- db-instance.ts defines the specs of DbInstance

  s3
  ├── constants.ts
  └── s3.ts

🚀 Build manifest

Just run yarn build

⚡ $ yarn build
yarn run v1.22.15
warning ../../../package.json: No license field
$ npx projen build
👾 build » default | ts-node --project tsconfig.dev.json .projenrc.ts
👾 build » compile | tsc --build
👾 build » post-compile » synth | cdk8s synth
No manifests synthesized
👾 build » test | jest --passWithNoTests --all --updateSnapshot
No tests found, exiting with code 0
----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
----------|---------|----------|---------|---------|-------------------
All files |       0 |        0 |       0 |       0 |
----------|---------|----------|---------|---------|-------------------
👾 build » test » eslint | eslint --ext .ts,.tsx --fix --no-error-on-unmatched-pattern src test build-tools .projenrc.js
Done in 25.90s.

Output directory

  dist
  ├── rds
  │   ├── rds-db-instance.yaml
  │   └── rds-subnet-group.yaml
  └── s3
      └── s3-test-bucket.yaml

We can now use the yaml files to create the AWS infrastructure through ACK

🚀 Conclusion

Although we have to import ACK CRDS resources for cdk8s API, we can manage k8s manifests through code

Vu Dao