di-terraform-repo-pull-controller

README

di-terraform-repo-pull-controller

In a GitOps deployment model, infrastructure changes are pulled from a source repository and applied asynchronously. This differs from the traditional "push" model where changes are pushed to a repo and then applied via a CI pipeline.

This repository implements a K8s controller that manages Repo resources and watches for new commits on a given repo url. When a new commit revision is pushed, the controller will schedule a Job to apply the Terraform changes.

Getting Started

# build controller
make build

# run units
make test

# deploy controller & CRD
make deploy

# create a custom resource Repo with a valid repo Url
kubectl apply -f https://raw.githubusercontent.com/davidmontoyago/di-terraform-repo-pull-controller-sample-repo/master/deployment/repo-resource.yaml

# check jobs created through the custom resource
kubectl get jobs

How It Works

The controller uses "Informers" to be notified of changes to Repo or Job resources. When a Repo resource is created, a RepoPoller goroutine will run to check the source repo for new revisions. When a new revision is found, its "Run" status will be updated to trigger the scheduling of a new Job to apply the changes. The repo "Run" status will be reconciled by syncHandler.

All Repo resource changes are processed via a work queue. From the original K8s sample-controller documentation:

workqueue is a rate limited work queue. This is used to queue work to be processed instead of performing it as soon as a change happens. This means we can ensure we only process a fixed amount of resources at a time, and makes it easy to ensure we are never processing the same item simultaneously in two different workers.

Controller Details

The controller makes use of the generators in k8s.io/code-generator to generate a typed client, informers, listers and deep-copy functions.

Re-generate the client:

make gen

The controller uses client-go library extensively. The details of interaction points of the sample controller with various mechanisms from this library are explained here.