Do you have an example of querying a custom resource?

[justinmchase]

trafficstars

I've created a custom resource definition and I see the api for CustomResourceDefinitions, but how do I then use this api to query for my custom resources?

[danopia]

Hey @justinmchase , The easiest way of getting an API for one of your own CRDs is by generating a client module based on your CustomResourceDefinition files and importing it into your program. This ensures that you have proper typing and validation available for working with your CRs.

Here's how I normally set this up. First, I have a directory in my project which contains my CRD files. For this example I'll create deploy/crds/crontab.yaml using the example CRD yaml from the kubernetes docs: https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/

Next I create a shell script generate-apis.sh which will invoke the codegen. I'll need to rerun this script in the future if I update the CRD schema, so I like committing this script to git:

#!/bin/sh -eux

# Regenerates the Kubernetes CR client modules.
CodegenSrc="https://raw.githubusercontent.com/cloudydeno/deno-kubernetes_apis/main/generation/run-on-crds.ts"
# Path to import /x/kubernetes_apis from, align this with your own imports.
ApisImportUrl="https://deno.land/x/[email protected]/"
InputDirectory="deploy/crds"
TargetDirectory="."

deno run --allow-read=. --allow-write=lib "$CodegenSrc" "$InputDirectory" "$TargetDirectory" "$ApisImportUrl"

At this point my project looks like this:

> tree
.
├── deploy
│   └── crds
│       └── crontab.yaml
└── generate-api.sh

Then I run that script:

> chmod +x ./generate-api.sh # just once after creating the script
> ./generate-api.sh
+ CodegenSrc=https://raw.githubusercontent.com/cloudydeno/deno-kubernetes_apis/main/generation/run-on-crds.ts
+ ApisImportUrl=https://deno.land/x/[email protected]/
+ deno run --allow-read=. --allow-write=lib https://raw.githubusercontent.com/cloudydeno/deno-kubernetes_apis/main/generation/run-on-crds.ts deploy/crds . https://deno.land/x/[email protected]/
Wrote lib/stable.example.com@v1/structs.ts
Wrote lib/stable.example.com@v1/mod.ts

And now I have a client module in a new lib/ directory:

> tree
.
├── deploy
│   └── crds
│       └── crontab.yaml
├── generate-api.sh
└── lib
    └── stable.example.com@v1
        ├── mod.ts
        └── structs.ts

From here this module can be imported like so, and used just like the built-in clients:

import { autoDetectClient } from 'https://deno.land/x/[email protected]/mod.ts';
const kubernetes = await autoDetectClient();

import { StableExampleComV1Api } from "./lib/stable.example.com@v1/mod.ts"
const exampleApi = new StableExampleComV1Api(kubernetes).namespace("default");

// just something arbitrary idk
await exampleApi.createCronTab({
  metadata: {
    name: 'my-crontab',
  },
  spec: {
    cronSpec: '@daily',
    image: 'cleanup-something',
    replicas: 1,
  },
});

Hopefully this is enough information to get the ball rolling for you. I didn't really have a good prior art when I set this up because I've found the kubernetes-client/javascript codegen workflow to be extremely subpar and unmaintainable when developing NodeJS programs, while the golang workflow is to generate the CRD yaml from your golang source code, which is usually the wrong direction for my projects.

Best, Dan

[justinmchase]

I sort of did this manually for now but this is a great comment and I hope anyone in the future with this issue follows this advice. Thank you!