Hiii 👋, Dhairya here. This is a summary of all the work I did for the kro (Kube Resource Orchestrator) and my personal experiences as a part of the Google Summer of Code 2025.
What is kro?
kro (Kube Resource Orchestrator) is an open-source, Kubernetes-native project that allows developers to define custom Kubernetes APIs using simple and straightforward configuration. With kro, one can easily configure new custom APIs that create a group of Kubernetes objects and the logical operations between them.
Why kro? - Manage any group of resources as one unit.
- Title : CLI for kro Resource Management
- Repository: kro-run/kro
- Mentors: Amine Hilaly, Barni S & kro Maintainers
- Project Size: Medium
- Contributor: Dhairya Majmudar
Let's dive deeper into the work I did with the amazing kro community, but before that, there are a few terms I will be referring to, so let me explain them first.
But before understanding what RGDs are, let's first understand what Kubernetes CRDs are.
A Kubernetes Custom Resource Definition (CRD) is a powerful mechanism that allows users to extend the Kubernetes API by defining their own custom resource types. These custom resources behave like built-in Kubernetes objects (e.g., Pods, Deployments) but are user-defined and tailored to specific application needs
Let's take a close and concise look at what RGDs are in kro.
kro RGDs taking CRDs a level up
When Kro is installed in a cluster, it installs a Custom Resource Definition (CRD) called ResourceGraphDefinition (RGD). The Platform, Security, and Compliance teams can collaborate to create custom APIs by defining Custom Resources for the ResourceGraphDefinition CRD.
let's take an example for better understanding
In the depicted example, the Platform Team has created a RGD with the name "Application Stack" that encapsulates the necessary resources, along with any additional logic, abstractions, and security best practices. When the RGD is applied to the cluster, a new API of kind ApplicationStack is created and available for the Developer to interact with. The Developers no longer need to directly manage the underlying infrastructure complexities, as the custom API handles the deployment and configuration of the required resources.
kro CLI Development
Building a CLI tool for kro resource management using GoLang's Cobra package.
Mentioned are the proposed tasks that are about to be completed under the project scope. Project goals:
- Build a CLI tool to help developers and admins manage kro.
- Create commands for common RGD operations [validate/generate].
- Open Container Images (OCI) management commands [package/push/pull/login/publish]
1. kro cli rootCmd #501
This PR adds the rootCmd to the kro CLI, which will be the main command entry point.
kro [SUB_COMMAND]
Screencast.from.2025-04-09.19-11-43.webm
2. kro validate #527
kro validate command is useful to validate the kro RGD file. Under the hood, it extends the kro DAG graph and internal kro checks to verify if RGD.
kro validate rgd -f [FILE]
Screencast.from.2025-06-13.20-11-43.webm
3. kro generate crd #583
kro generate crd command is able to generate the CRD file from the given kro RGD file.
kro generate crd -f [FILE]
Flags:
| Shorthand | Flag | Usage |
|---|---|---|
| -f | --file | Path to the ResourceGroupDefinition file |
| -F | --format | Output format (yaml/json) |
| -o | --output | Path to the output file |
Screencast.from.2025-06-13.20-25-09.webm
4. kro generate diagram #589
kro generate diagram command can be used to visualise the resource dependency graph. This command generates an HTML file that shows the directed graph between resources of the given RGD file.
kro generate diagram -f [FILE]
Flags:
| Shorthand | Flag | Usage |
|---|---|---|
| -f | --file | Path to the ResourceGroupDefinition file |
Screencast.from.2025-07-15.22-45-05.webm
5. kro generate instance #603
kro generate instance command is used to generate a dummy instance for the given RGD file.
kro generate instance -f [FILE]
Flags:
| Shorthand | Flag | Usage |
|---|---|---|
| -f | --file | Path to the ResourceGroupDefinition file |
Screencast.from.2025-07-15.23-44-11.webm
6. kro package #617
kro package command is useful to package a given kro RGD file into an OCI-compatible image. This image can be further published into remote container registries like Docker Hub, AWS, GCR, etc...
kro package -f [FILE] -t [TAG]
Flags:
| Shorthand | Flag | Usage |
|---|---|---|
| -f | --file | Path to the ResourceGroupDefinition file |
| -t | --tag | Tag to the image, Default: Latest |
kro-package.webm
7. kro publish #655
kro publish command is useful to publish an OCI image to a given remote container registry. This command also accepts username and password from the user for authentication to the registry
kro package -f [FILE] -r [REGISTRY_URL] -u [USER_NAME] -p [PASSWORD]
Flags:
| Shorthand | Flag | Usage |
|---|---|---|
| -f | --file | Path to the ResourceGroupDefinition file |
| -r | --ref | Remote reference to publish the OCI image to (e.g., 'ghcr.io/user/repo:tag') |
| -u | --username | Username for the remote registry (Optional) |
| -p | --password | Password for the remote registry (Optional) |
Note: If username or password is not provided via flags, the CLI will prompt the user to provide them in further steps.
kro-publish.webm
8. kro login #656
The kro cli login command is used to store user credentials (passwords, username) for different registers into the config file.
storage location: $HOME/.config/kro/registry/config.json
kro login -f [FILE] -r [REGISTRY_URL] -u [USER_NAME] -p [PASSWORD]
Flags:
| Shorthand | Flag | Usage |
|---|---|---|
| -f | --file | Path to the ResourceGroupDefinition file |
| -r | --ref | Remote reference to publish the OCI image to (e.g., 'ghcr.io/user/repo:tag') |
| -u | --username | Username for the remote registry (Optional) |
| -p | --password | Password for the remote registry (Optional) |
Note: If username or password is not provided via flags, the CLI will prompt the user to provide them in further steps.
Screencast.from.2025-08-31.20-16-24.webm
As the Google Summer of Code comes to an end, I see a miniature version of myself trying to learn and get into such an amazing organization, fearing to start something new and big. But fast-forward to today, I have learned and grown a lot as a developer and as a person. I will always be indebted to kro for helping me in this journey and for being such a great organization and developer community. The people, mentors, and everyone are so helpful and supportive that I have always hoped to be in such an organization.
I learned so many things during this journey, from learning how to write industry-level Golang code to writing good commit messages and using different packages to build various kinds of CLI commands.
I had a great time working with the kro community, and I am really grateful to my mentors, Amine Hilaly and Barni S, and all the organization members, for helping me throughout this journey.
Thank you, kro, for making this summer the most memorable journey of learning and growth. 🚀 💙