crd2pulumi

crd2pulumi

Generate strongly-typed CustomResources based on a Kubernetes CustomResourceDefinition (CRD).

Goals

crd2pulumi is a CLI tool that generates strongly-typed CustomResources based on a Kubernetes CRD. CustomResourceDefinitions allow you to extend the Kubernetes API by defining your schemas for custom objects. Pulumi lets you create CustomResources, but previously there was no strong-typing for these objects since every schema was, well, custom. This can be a massive headache for popular CRDs such as cert-manager or istio, which contain thousands of lines of complex YAML schemas. By generating strongly-typed versions of CustomResources, crd2pulumi makes filling out their arguments more convenient because it lets you leverage existing IDE type checking and autocomplete features.

Currently, TypeScript and Go are supported, with Python and .NET coming soon.

Building and Installation

If you wish to use crd2pulumi without developing the tool itself, you can use one of the binary releases hosted on GitHub.

crd2pulumi uses Go modules to manage dependencies. If you want to develop crd2pulumi itself, you'll need to have Go installed in order to build. Once this prerequisite is installed, run the following to build the crd2pulumi binary and install it into $GOPATH/bin:

$ go build -o $GOPATH/bin/crd2pulumi main.go

Go should automatically handle pulling the dependencies for you.

If $GOPATH/bin is not on your path, you may want to move the crd2pulumi binary from $GOPATH/bin into a directory that is on your path.

Usage

$ crd2pulumi <language> <crd file path> [output directory] [--force]

<language> is the target language to generate code for, so either nodejs or go.

<crd file path> is the path to the k8s CRD YAML file.

[output directory] is an optional path to the directory in which to output the code to. If this field is not specified, then crd2pulumi will automatically output to the same directory as the CRD YAML file.

[--force] is an optional flag to overwrite existing files if crd2pulumi would write to directories or files that already exist. By default this is set to false.

Examples

Let's use the example CronTab CRD specified in resourcedefinition.yaml from the Kubernetes Documentation.

Output to TypeScript

To generate a strongly-typed CronTab CustomResource in TypeScript, we can run this command:

$ crd2pulumi nodejs resourcedefinition.yaml

By default, this will create the folder ./crontabs in the same directory as resourcedefinition.yaml. Each versioned CustomResource will live under this folder, so since we had just specified v1, you'll see that a ./crontabs/v1 directory has been created. If we had defined a v2 version in the CRD YAML file, you'd also see ./crontabs/v2.

./crontabs contains two useful classes: v1.CronTab and CronTabDefinition. v1.Crontab is the typed CustomResource for CronTab, and CronTabDefinition is a helper class that provisions the CRD YAML schema in a single line. Now let's import the generated code into a Pulumi program that provisions the CRD and creates an instance of it.

import * as crontabs from "./crontabs"
import * as pulumi from "@pulumi/pulumi"

const cronTabDefinition = new crontabs.CronTabDefinition("my-crontab-definition")

const myCronTab = new crontabs.v1.CronTab("my-new-cron-object",
{
    metadata: {
        name: "my-new-cron-object",
    },
    spec: {
        cronSpec: "* * * * */5",
        image: "my-awesome-cron-image",
    }
})

export const urn = myCronTab.urn;

As you can see, the v1.CronTab object is typed! For example, if you try to set cronSpec to a non-string or add an extra field, your IDE should immediately warn you.

Output to Go

Here's an example of the same program, but written in Go. To generate a strongly-typed CronTab CustomResource, we can run this command:

$ crd2pulumi go resourcedefinition.yaml

Like with TypeScript, this will create a ./crontabs folder. If we had multiple versions, they would be generated in ./crontabs/v2/crontabs.go, ./crontabs/v3/crontabs.go, etc...

Now we can access the NewCronTab() constructor. Create a main.go file with the following, swapping out the go_pulumi in import crontabs "go_pulumi/v1" with your own module's name.

package main

import (
  crontabs "go_pulumi/v1"

  v1 "github.com/pulumi/pulumi-kubernetes/sdk/v2/go/kubernetes/apiextensions/v1"
  metav1 "github.com/pulumi/pulumi-kubernetes/sdk/v2/go/kubernetes/meta/v1"
  "github.com/pulumi/pulumi/sdk/v2/go/pulumi"
)

func main() {
	pulumi.Run(func(ctx *pulumi.Context) error {
		// Register the CronTab CRD.
		_, err := yaml.NewConfigFile(ctx, "my-crontab-definition",
			&yaml.ConfigFileArgs{
				File: "resourcedefinition.yaml",
			},
		)
		if err != nil {
      return err
		}
		// Instantiate a CronTab resource.
		cronTabInstance, err := crontabs.NewCronTab(ctx, "my-new-cron-object",
			&crontabs.CronTabArgs{
				Metadata: metav1.ObjectMetaArgs{
					Name: pulumi.StringPtr("my-new-cron-object"),
				},
				Spec: crontabs.CronTabSpecArgs{
					CronSpec: pulumi.StringPtr("* * * * */5"),
					Image:    pulumi.StringPtr("my-awesome-cron-image"),
				},
			},
		)
		if err != nil {
			return err
		}
		ctx.Export("urn", cronTabInstance.URN())
		return nil
	})
}

You can use the generated crontabs.CronTabSpecArgs struct to ensure your arguments are valid! This is a great improvement compared to filling out a map[string]interface{}, which was the previous procedure for Kubernetes CustomResources.

Now let's run the program and perform the update.

$ pulumi up
Previewing update (dev):
  Type                                                      Name                Plan
  pulumi:pulumi:Stack                                       examples-dev
 +   ├─ kubernetes:stable.example.com:CronTab                   my-new-cron-object  create
 +   └─ kubernetes:apiextensions.k8s.io:CustomResourceDefinition  my-crontab-definition  create
Resources:
  + 2 to create
  1 unchanged
Do you want to perform this update? yes
Updating (dev):
  Type                                                      Name                Status
  pulumi:pulumi:Stack                                       examples-dev
 +   ├─ kubernetes:stable.example.com:CronTab                   my-new-cron-object  created
 +   └─ kubernetes:apiextensions.k8s.io:CustomResourceDefinition  my-crontab-definition  created
Outputs:
  urn: "urn:pulumi:dev::examples::kubernetes:stable.example.com/v1:CronTab::my-new-cron-object"
Resources:
  + 2 created
  1 unchanged
Duration: 17s
Permalink: https://app.pulumi.com/albert-zhong/examples/dev/updates/4

It looks like both the CronTab definition and instance were both created! Finally, let's verify that they were created by manually viewing the raw YAML data:

$ kubectl get ct -o yaml

- apiVersion: stable.example.com/v1
  kind: CronTab
  metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"stable.example.com/v1","kind":"CronTab","metadata":{"labels":{"app.kubernetes.io/managed-by":"pulumi"},"name":"my-new-cron-object"},"spec":{"cronSpec":"* * * * */5","image":"my-awesome-cron-image"}}
  creationTimestamp: "2020-08-10T09:50:38Z"
  generation: 1
  labels:
    app.kubernetes.io/managed-by: pulumi
  name: my-new-cron-object
  namespace: default
  resourceVersion: "1658962"
  selfLink: /apis/stable.example.com/v1/namespaces/default/crontabs/my-new-cron-object
  uid: 5e2c56a2-7332-49cf-b0fc-211a0892c3d5
  spec:
  cronSpec: '* * * * */5'
  image: my-awesome-cron-image
kind: List
metadata:
  resourceVersion: ""
  selfLink: ""