mirror of https://github.com/fluxcd/flux2.git
Add source watcher dev guide
stefanprodan
5 years ago
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# Watching for source changes
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In this guide you'll be developing a Kubernetes controller with
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[Kubebuilder](https://github.com/kubernetes-sigs/kubebuilder)
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that subscribes to [GitRepository](../components/source/gitrepositories.md)
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events and reacts to revision changes by downloading the artifact produced by
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[source-controller](../components/source/controller.md).
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## Prerequisites
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On your dev machine install the following tools:
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* go >= 1.13
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* kubebuilder >= 2.3
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* kind >= 0.8
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* kubectl >= 1.18
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* kustomize >= 3.5
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* docker >= 19.03
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## Install the GitOps Toolkit
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Create a cluster for testing:
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```sh
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kind create cluster --name dev
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```
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Install the toolkit CLI:
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```sh
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curl -s https://toolkit.fluxcd.io/install.sh | sudo bash
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```
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Verify that your dev machine satisfies the prerequisites with:
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```sh
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tk check --pre
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```
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Install the toolkit controllers on the dev cluster:
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```sh
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tk install
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```
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## Clone the sample controller
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You'll be using [stefanprodan/source-watcher](https://github.com/stefanprodan/source-watcher) as
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a template for developing your own controller. The source-watcher was scaffolded with `kubebuilder init`.
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Clone the source-watcher repo:
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```sh
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git clone https://github.com/stefanprodan/source-watcher
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cd source-watcher
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```
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Build the controller:
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```sh
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make
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```
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## Run the controller
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Port forward to source-controller artifacts server:
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```sh
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kubectl -n gitops-system port-forward svc/source-controller 8181:80
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```
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Export the local address as `SOURCE_HOST`:
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```sh
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export SOURCE_HOST=localhost:8181
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```
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Run source-watcher locally:
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```sh
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make run
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```
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Create a Git source:
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```sh
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tk create source git test \
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--url=https://github.com/stefanprodan/podinfo \
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--tag=4.0.0
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```
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The source-watcher should log the revision:
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```console
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New revision detected {"gitrepository": "gitops-system/test", "revision": "4.0.0/ab953493ee14c3c9800bda0251e0c507f9741408"}
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Extracted tarball into /var/folders/77/3y6x_p2j2g9fspdkzjbm5_s40000gn/T/test292235827: 123 files, 29 dirs (32.603415ms)
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Processing files...
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```
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Change the Git tag:
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```sh
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tk create source git test \
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--url=https://github.com/stefanprodan/podinfo \
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--tag=4.0.1
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```
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The source-watcher should log the new revision:
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```console
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New revision detected {"gitrepository": "gitops-system/test", "revision": "4.0.1/113360052b3153e439a0cf8de76b8e3d2a7bdf27"}
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```
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The source-controller reports the revision under `GitRepository.Status.Artifact.Revision` in the format: `<branch|tag>/<commit>`.
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## How it works
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The [GitRepositoryWatcher](https://github.com/stefanprodan/source-watcher/blob/master/controllers/gitrepository_watcher.go)
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controller does the following:
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* subscribes to `GitRepository` events
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* detects when the Git revision changes
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* downloads and extracts the source artifact
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* write to stdout the extracted file names
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```go
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// GitRepositoryWatcher watches GitRepository objects for revision changes
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type GitRepositoryWatcher struct {
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client.Client
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Log logr.Logger
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Scheme *runtime.Scheme
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}
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// +kubebuilder:rbac:groups=source.fluxcd.io,resources=gitrepositories,verbs=get;list;watch
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// +kubebuilder:rbac:groups=source.fluxcd.io,resources=gitrepositories/status,verbs=get
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func (r *GitRepositoryWatcher) Reconcile(req ctrl.Request) (ctrl.Result, error) {
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// set timeout for the reconciliation
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ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
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defer cancel()
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// get source object
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var repository sourcev1.GitRepository
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if err := r.Get(ctx, req.NamespacedName, &repository); err != nil {
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return ctrl.Result{}, client.IgnoreNotFound(err)
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}
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log := r.Log.WithValues(strings.ToLower(repository.Kind), req.NamespacedName)
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log.Info("New revision detected", "revision", repository.Status.Artifact.Revision)
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// create tmp dir
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tmpDir, err := ioutil.TempDir("", repository.Name)
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if err != nil {
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return ctrl.Result{}, fmt.Errorf("unable to create temp dir, error: %w", err)
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}
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defer os.RemoveAll(tmpDir)
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// download and extract artifact
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summary, err := r.fetchArtifact(ctx, repository, tmpDir)
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if err != nil {
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return ctrl.Result{}, fmt.Errorf("unable to fetch artifact, error: %w", err)
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}
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log.Info(summary)
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// list artifact content
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files, err := ioutil.ReadDir(tmpDir)
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if err != nil {
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return ctrl.Result{}, fmt.Errorf("unable to list files, error: %w", err)
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}
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// do something with the artifact content
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for _, f := range files {
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log.Info("Processing " + f.Name())
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}
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return ctrl.Result{}, nil
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}
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func (r *GitRepositoryWatcher) SetupWithManager(mgr ctrl.Manager) error {
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return ctrl.NewControllerManagedBy(mgr).
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For(&sourcev1.GitRepository{}).
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WithEventFilter(GitRepositoryRevisionChangePredicate{}).
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Complete(r)
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}
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```
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To add the watcher to an existing project, copy the controller and the revision change predicate to your `controllers` dir:
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* [gitrepository_watcher.go](https://github.com/stefanprodan/source-watcher/blob/master/controllers/gitrepository_watcher.go)
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* [gitrepository_predicate.go](https://github.com/stefanprodan/source-watcher/blob/master/controllers/gitrepository_predicate.go)
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In your `main.go` init function, register the Source API schema:
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```go
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import sourcev1 "github.com/fluxcd/source-controller/api/v1alpha1"
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func init() {
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_ = clientgoscheme.AddToScheme(scheme)
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_ = sourcev1.AddToScheme(scheme)
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// +kubebuilder:scaffold:scheme
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}
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```
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Start the controller in the main function:
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```go
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func main() {
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if err = (&controllers.GitRepositoryWatcher{
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Client: mgr.GetClient(),
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Log: ctrl.Log.WithName("controllers").WithName("GitRepositoryWatcher"),
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Scheme: mgr.GetScheme(),
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}).SetupWithManager(mgr); err != nil {
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setupLog.Error(err, "unable to create controller", "controller", "GitRepositoryWatcher")
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os.Exit(1)
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}
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}
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```
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Note that the watcher controller depends on Kubernetes client-go >= 1.18.
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Your `go.mod` should require controller-runtime v0.6 or newer:
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```go
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require (
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k8s.io/apimachinery v0.18.4
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k8s.io/client-go v0.18.4
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sigs.k8s.io/controller-runtime v0.6.0
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)
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```
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That's it! Happy hacking!
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