A Porter Mixin Skeleton

This repository contains the skeleton structure of a Porter Mixin. You can clone this repository and use it as a starting point to build new mixins. The structure of this project matches closely with existing Porter Mixins.

Create a new repository in GitHub using this repository as a template.
Go 1.17 or higher is required. You can choose to clone into the GOPATH or not according to preference.
Rename the cmd/skeletor and pkg/skeletor directories to cmd/YOURMIXIN and pkg/YOURMIXIN.
Find any remaining skeletor text in the repository and replace it with YOURMIXIN.
In pkg/YOURMIXIN/version.go replace YOURNAME with the name you would like displayed as the mixin author. This value is displayed as the author of your mixin when porter mixins list is run.
Replace the YOURNAME instances in pkg/YOURMIXIN/version_test.go with the name used above.
Run mage build test to try out all the make targets and verify that everything executes without failing. You may need to fix a test string or two.
Run mage install to install your mixin into the Porter home directory. If you don't already have Porter installed, install it first.
Now your mixin is installed, you are ready start customizing and iterating on your mixin!

Customize your mixin

This mixin is ready to wrap an existing command-line tool. The shortest path would be to edit build.go to add the instructions to download the tool and you are all set. It will look and feel like the gcloud or aws mixins, both of which are built on top of the exec mixin.

Edit the Build function in pkg/skeletor/build.go. Here you can add any Dockerfile lines that you require to download and install additional tools, configuration files, etc necessary for your mixin. The Build function should write the Dockerfile lines to m.Out which is a pipe from the mixin back to porter. You will also find the basic logic supporting mixin configuration. Support for clientVersion is ready to go, which enables users to specify the version of the underlying tool/utility provided by the mixin, if applicable.

Search for TODO in the code and follow the instructions to customize the mixin.

Here is an example from the aws mixin, where it downloads the latest version of of the aws binary and installs it:

https://github.com/getporter/aws-mixin/blob/001c19bfe06d248143353a55f07a42c913579481/pkg/aws/build.go#L7

This is enough to have a working mixin. Run mage build install and then test it out with a bundle.

That will get you started but make sure to read the mixin developer documentation for how to create a full featured mixin:

Once ready for primetime, don't forget to revisit this README.md and update/replace it with details on your mixin.

Project Structure

In the cmd/skeletor directory, you will find a cli built using spf13/cobra. The CLI contains a go file for each basic capability a Mixin should implement:

build
schema
version
install
upgrade
invoke
uninstall

Each of these command implementations have a corresponding Mixin implementation in the pkg/skeletor directory. Each of the commands above is wired into an empty implementation in pkg/skeletor that needs to be completed. In order to build a new Mixin, you need to complete these implementations with the relevant technology. For example, to build a Cloud Formation mixin, you might implement the methods in pkg/skeletor using the AWS Go SDK.

Provided capabilities

This skeleton mixin project brings some free capabilities:

File System Access and Context

Porter provides the portercontext package that has helpful mechanisms for accessing the File System using spf13/afero. This makes it easy to provide mock File System implementations during testing. The portercontext package also provides a mechanism to encapsulate stdin, stdout and stderr so that they can easily be passed from cmd/skeletor code to implementing pkg/skeletor code.

Template and Static Asset Handling

The project go:embed for dealing with static files, such as templates or other content that is best modeled outside of a Go file. You can see an example of this in pkg/skeletor/schema.go.

Basic Schema

The project provides an implementation of the skeletor schema command that is mostly functional. To fully implement this for your mixin, you simply need to provide a valid JSON schema. For reference, consult pkg/skeletor/schema/schema.json.

Basic Tests

The project provides some very basic test skeletons that you can use as a starting point for building tests for your mixin.

Magefile

The project also includes a Magefile that is used to build, test, and publish the mixin.

Publish

You must set the GITHUB_TOKEN environment variable with your personal access token in order to use the default publish target.

Publish uploads cross-compiled binaries of your mixin to a GitHub release. You must set the PORTER_RELEASE_REPOSITORY environment variable to your GitHub repository name, e.g. github.com/YOURNAME/YOURREPO. There is a placeholder in the Publish magefile target where you can set that value.

Create a tag, for example git tag v0.1.0, and push it to your repository. Run mage XBuildAll Publish to build your mixin and upload the binaries to the github release for that tag. If the commit is not tagged, the release is named "canary".

If you want to generate a mixin feed file (atom.xml), edit the Publish magefile target, uncomment out the rest of the function, and set the PORTER_PACKAGES_REMOTE environment variable to a repository where the atom.xml file should be committed. For example, Porter uses github.com/getporter/packages for publishing our mixin feed.

squillace/curl