Foghorn 📯

Foghorn is a fully Kubernetes-native CI system, inspired by prow. It's powered by Tekton Pipelines, which provides a number of handy abstractions for defining CI pipelines in a k8s-native way. Foghorn provides webhook handling and some git-centric CommentOps features, and it supports multiple git providers.

Architecture

There are two logical groupings of components in Foghorn:

• Catcher
  • A highly-available webhook handler. Analogous to hook in Prow.
• Controllers
  • Controllers for Foghorn's CRDs, GitEvent and Action
  • contains the bulk of Foghorn's business logic

The way this works is that Catcher receives a webhook from a git provider (GitHub, Gitlab, Bitbucket, etc.) and creates a GitEvent resource, which contains a webhook that has been parsed into a generic struct using go-scm.

The GitEvent controller then picks up the newly created GitEvent and determines what should happen next, e.g., run a Tekton pipeline, label an issue on the git provider, etc. It then creates an Action resource that will encapsulate data about the required action, at which point the Action controller takes over and monitors the action, recording any changes to its state.

Catcher is designed to run in a dedicated binary, while the controllers can be run either as a single, monolithic binary or as separate, dedicated binaries. By running them separately, you have the option of replacing one of the provided controllers with a controller of your own if you wish to override the default behavior of that controller. You can also add a controller to extend Foghorn's capabilities in either scenario.

Building

The fastest way to get started hacking on Foghorn is with ko.

If you take a look in deployments, everything should look normal except for the following field in 200-catcher-deployment.yaml:

image: github.com/foghornci/foghorn/cmd/catcher

The magic of ko is that it will:

• automatically build the go binary whose code is specified in the image field
• package it into an image
• push the image to a configured image registry
• update the deployment manifest with the newly build image name and tag
• kubectl apply a collection of k8s manifest files

Once you've installed and configured ko, simply run the following from the project root:

ko apply -f deployments/

This will build and deploy Foghorn to your Kubernetes cluster. In addition to a deployment, it will create a service and ingress so that you can start receiving webhooks right away, and it will put all of it in a namespace called foghorn. Simply re-run the command to build and deploy your latest changes. It's idempotent, so running it multiple times with no changes in between will have no effect.