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How to Contribute

The Crossplane project is under Apache 2.0 license. We accept contributions via GitHub pull requests. This document outlines some of the conventions related to development workflow, commit message formatting, contact points and other resources to make it easier to get your contribution accepted.

Certificate of Origin

By contributing to this project you agree to the Developer Certificate of Origin (DCO). This document was created by the Linux Kernel community and is a simple statement that you, as a contributor, have the legal right to make the contribution. See the DCO file for details.

Contributors sign-off that they adhere to these requirements by adding a Signed-off-by line to commit messages. For example:

This is my commit message

Signed-off-by: Random J Developer <>

Git even has a -s command line option to append this automatically to your commit message:

git commit -s -m 'This is my commit message'

If you have already made a commit and forgot to include the sign-off, you can amend your last commit to add the sign-off with the following command, which can then be force pushed.

git commit --amend -s

We use a DCO bot to enforce the DCO on each pull request and branch commits.

Getting Started

  • Fork the repository on GitHub
  • Read the install for build and test instructions
  • Play with the project, submit bugs, submit patches!

Contribution Flow

This is a rough outline of what a contributor's workflow looks like:

  • Create a branch from where you want to base your work (usually master).
  • Make your changes and arrange them in readable commits.
  • Make sure your commit messages are in the proper format (see below).
  • Push your changes to the branch in your fork of the repository.
  • Make sure all tests pass, and add any new tests as appropriate.
  • Submit a pull request to the original repository.


Details about building crossplane can be found in

Coding Style

Crossplane projects are written in golang and follows the style guidelines dictated by the go fmt as well as go vet tools.


Comments should be added to all new methods and structures as is appropriate for the coding language. Additionally, if an existing method or structure is modified sufficiently, comments should be created if they do not yet exist and updated if they do.

The goal of comments is to make the code more readable and grokkable by future developers. Once you have made your code as understandable as possible, add comments to make sure future developers can understand (A) what this piece of code's responsibility is within Crossplane's architecture and (B) why it was written as it was.

The below blog entry explains more the why's and how's of this guideline.

For Go, Crossplane follows standard godoc guidelines. A concise godoc guideline can be found here:

Commit Messages

We follow a rough convention for commit messages that is designed to answer two questions: what changed and why. The subject line should feature the what and the body of the commit should describe the why.

aws: add support for RDS controller

this commit enables controllers and apis for RDS. It
enables provisioning a RDS database.

The format can be described more formally as follows:

<subsystem>: <what changed>
<why this change was made>

The first line is the subject and should be no longer than 70 characters, the second line is always blank, and other lines should be wrapped at 80 characters. This allows the message to be easier to read on GitHub as well as in various git tools.

Adding New Resources

Project Organization

The Crossplane project is based on and intially created by using Kubebuilder is a framework for building Kubernetes APIs.

The Crossplane project organizes resources (api types and controllers) by grouping them by Cloud Provider with further sub-group by resource type

The Kubebuilder framework does not provide good support for projects with multiple groups and group tiers which contain resources with overlapping names. For example:

├── apis
│   ├── aws
│   │   ├── apis.go
│   │   └── database
│   │       ├── group.go
│   │       └── v1alpha1
│   │           ├── doc.go
│   │           ├── rds_instance_types.go
│   │           ├── rds_instance_types_test.go
│   │           ├── register.go
│   │           ├── v1alpha1_suite_test.go
│   │           └── zz_generated.deepcopy.go
│   └── gcp
│       ├── apis.go
│       └── database
│           ├── group.go
│           └── v1alpha1
│               ├── cloudsql_instance_types.go
│               ├── cloudsql_instance_types_test.go
│               ├── doc.go
│               ├── register.go
│               ├── v1alpha1_suite_test.go
│               └── zz_generated.deepcopy.go
└── controller
    ├── aws
    │   ├── controller.go
    │   └── database
    │       ├── database_suite_test.go
    │       ├── rds_instance.go
    │       └── rds_instance_test.go
    └── gcp
        ├── controller.go
        └── database
            ├── cloudsql_instance.go
            ├── cloudsql_instance_test.go
            └── database_suite_test.go

In above example we have two groups with sub-group (tiers):

  • aws/rds
  • gcp/cloudsql

In addition both groups contain types with the same name: Instance

Creating New Resource

There are several different ways you can approach the creation of the new resources:


Good ol' copy & paste of existing resource for both apis and controller (if new controller is needed for your resource) and update the copied code to tailor your needs.

Kubebuilder With New Project

Create and Initialize a new (temporary) kubebuilder project and create new resources: apis and controller(s), then copy them into Crossplane project following the established project organization.

To verify that new artifacts run:

make build test

Local Build and Test

To learn more about the developer iteration workflow, including how to locally test new types/controllers, please refer to the Local Build instructions.