Enable cdk8s to programmatically generate kubernetes yaml

[dodtsair]

Description of the feature or enhancement:

Cdk8s should have APIs enabling the generation of kubernetes yaml. Calling this API on the current chart would produce the yaml for that chart, much like calling synth from the command line. Where the command line synth's the chart into a file, the API call would synth the chart into memory for use with other tools.

Use Case:

CDK EKS has the ability to addResource into an EKS cluster. That API call takes a string as it argument. To do this with cdk8s I would have to run cdk8s from the command line, then UI filesystem APIs to find the produced file, load that file into memory and then call addResource.

If cdk8s had the ability to generate kubernetes yaml via API call into memory. It could be treated as a CDK construct or extension of the CDK. Consuming information from other CDK constructs and producing information for other CDK constructs.

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This is a 🚀 Feature Request
Whats this line above mean?

[J11522]

Have a look at the following issues:
#48
aws/aws-cdk#9670

Is that what you are trying to achieve?

Depending on your setup, the solution proposed in #48 (comment) works like a charm. Mind the different versions of the constructs library being used.
This can be solved by creating a separate app scope if possible, but in some use cases you could run in the issue described here:
aws/aws-cdk#9670

[dodtsair]

@J11522 yeah, 9670 is basically the same thing. I would close this in favor of 9670

I have had other conversations that 9670 also covers to some degree. For example if I want to use efs filesystem in my cluster I would need the efs filesystem id that was created by the CDK which I could then use in cdk8s as volumeHandle to generate the necessary manifest as documented here: https://docs.aws.amazon.com/eks/latest/userguide/efs-csi.html

apiVersion: v1
kind: PersistentVolume
metadata:
  name: efs-pv
spec:
  capacity:
    storage: 5Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: efs-sc
  csi:
    driver: efs.csi.aws.com
    volumeHandle: fs-582a03f3

One of my original thoughts was to have the cdk8s build a yaml file, convert it to json and mark that file as the main file for that project. Then use npm to require that project into my cdk project. I believe this would work, I'll try it later. But this doesn't allow me to take data from the cdk into cdk8s for the manifest that cdk will ultimately apply to the cluster.

[iliapolo]

@dodtsair I'm closing this because the behavior requested here is available through chart.toJson.

As far as integrating with EKS, please follow aws/aws-cdk#9670 for more details and progress.

Thanks