Flux oci support 7: unit tests for OCI support in flux plugin

cmd/kubeapps-apis/plugins/fluxv2/packages/v1alpha1/OCI_TERMINOLOGY.md

@@ -0,0 +1,122 @@
+# OCI TERMINOLOGY
+
+Note the differences between various technologies:
+
+## Flux
+
+Given an OCI HelmRepository CRD with URL like `"oci://ghcr.io/stefanprodan/charts"` or `"oci://ghcr.io/stefanprodan/charts/"` (URL ending with a slash), then:
+- `oci://ghcr.io/stefanprodan/charts` is the *OCI chart repository* URL with the following components:
+  - `oci://` - URL scheme, indicating this is an *OCI chart repository*, as opposed to an *HTTP chart repository*
+  - `ghcr.io` - OCI registry host
+  - `/stefanprodan/charts` - registry path
+- That OCI registry may contain multiple helm chart repositories, such as `"podinfo"` and `"nginx"`. The associated OCI references would be: 
+  - `oci://ghcr.io/stefanprodan/charts/podinfo`
+  - `oci://ghcr.io/stefanprodan/charts/nginx`
+- Each of the repositories may only contain a single chart, whose name matches that of the repository basename. For example, repository with the basename (the last segment of the URL path) `"podinfo"` may only contain a single chart also called `"podinfo"`. Also see helm section below.
+- Each of the charts may have multiple versions a.k.a. tags, e.g. "`6.1.5"`, `"6.1.4"`, etc.
+
+References:
+  - https://fluxcd.io/docs/components/source/helmrepositories/
+  - https://github.com/fluxcd/flux2/tree/main/rfcs/0002-helm-oci
+  - https://github.com/fluxcd/source-controller/blob/main/controllers/helmrepository_controller_oci.go
+
+## ORAS v2 go libraries
+Given a remote OCI registry, such as `ghcr.io`, will list all repository names hosted in the format `"{REGISTRY_PATH}/{NAME}"`. Unlike the flux section, REGISTRY_PATH does not begin with a slash. For example, assuming the remote registry with the URL `"oci://ghcr.io/stefanprodan/charts"` contains 2 repositories, `"podinfo"` and `"podinfo-2"`, then the following list is returned from ORAS `Registry.Repositories()` API:
+  1. `"stefanprodan/charts/podinfo"`
+  2. `"stefanprodan/charts/podinfo-2"`
+
+References: 
+  - https://github.com/distribution/distribution/blob/main/docs/spec/api.md#listing-repositories
+  - https://oras.land/ 
+  - https://github.com/oras-project/oras-go/blob/14422086e41897a44cb706726e687d39dc728805/registry/remote/url.go#L43
+
+## Helm
+
+One can login to or logout from a registry host, such as
+```
+$ helm registry login ghcr.io -u $GITHUB_USER -p $GITHUB_TOKEN
+```
+and 
+```
+$ helm registry logout ghcr.io
+Logout succeeded
+```
+Here `ghcr.io` is the registry host
+
+From [helm docs](https://helm.sh/docs/topics/registries/):
+```
+When using helm push to upload a chart to an OCI registry, the reference must be prefixed with oci:// and must not contain the basename or tag
+
+The registry reference basename is inferred from the chart's name, and the tag is inferred from the chart's semantic version
+
+Certain registries require the repository and/or namespace (if specified) to be created beforehand
+```
+
+From [helm HIPS spec](https://github.com/helm/community/blob/main/hips/hip-0006.md#4-chart-names--oci-reference-basenames):
+```
+To keep things simple, the basename (the last segment of the URL path) on a registry reference should be equivalent to the chart name.
+
+For example, given a chart with the name pepper and the version 1.2.3, users may run a command such as the following:
+
+$ helm push pepper-1.2.3.tgz oci://r.myreg.io/mycharts
+
+which would result in the following reference:
+
+oci://r.myreg.io/mycharts/pepper:1.2.3
+
+By placing such restrictions on registry URLs Helm users are less likely to do "strange things" with charts in registries
+```
+
+In this case:
+    - a single repository named `"mycharts/pepper"` will be created if one does not exist
+    - the repository contains a chart named `"pepper"`
+    - the chart `"pepper"` has a version `"1.2.3"`   
+
+You can use the command ```helm show all``` to see (some) information about the `"pepper"` chart:
+```
+$ helm show all oci://r.myreg.io/mycharts/pepper | head -9 
+apiVersion: v1
+appVersion: 1.2.3
+description: ...
+home: ...
+kubeVersion: '>=1.19.0-0'
+maintainers:
+- email: stefanprodan@users.noreply.github.com
+  name: stefanprodan
+name: pepper
+...
+```
+
+References:
+  - https://helm.sh/blog/storing-charts-in-oci/
+  - https://helm.sh/docs/topics/registries/
+  - https://github.com/helm/community/blob/main/hips/hip-0006.md#specification
+
+## GitHub Container Registry `ghcr.io`
+Take an OCI registry URL like `"oci://ghcr.io/gfichtenholt/charts/podinfo:6.1.5"`
+GitHub Container Registry WebPortal, CLI and API do not use the term *"OCI registry"* and *"OCI repository"*. Instead, the following terms are used.
+  - **Host** - always `ghcr.io`
+  - **Owner** - may be an organization or a indiviual account,e.g. `stefanprodan`
+  - **Package** - with package type `container`, e.g. `charts/podinfo`
+  - **Package Version** - package version a.k.a. tag, e.g. `"6.1.5"`
+
+The term `package` seems to correspond to be a concatenation of an last segment of an OCI repository path and chart name, `charts/podinfo` in the example above. The following list shows a URL used with `helm push` command and the resulting package name on `ghcr.io`:
+  - oci://ghcr.io/gfichtenholt - podinfo
+  - oci://ghcr.io/gfichtenholt/charts - charts/podinfo
+  - oci://ghcr.io/gfichtenholt/charts/podinfo - charts/podinfo/podinfo
+
+A given owner may have mutiple packages, e.g. `"nginx/nginx"`, `"charts/podinfo"`, etc. A given package may have multiple versions. The use case with multiple charts in the same repository doesn't really apply (TODO double check if there is a workaround)
+
+References:
+  - https://docs.github.com/en/rest/packages
+  - https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry
+  - https://github.com/gfichtenholt?tab=packages
+
+---
+Here is probably the most confusing part of the whole document:
+  1. Assume we have a Flux OCI HelmRepository CRD with URL `"oci://ghcr.io/gfichtenholt/helm-charts"` 
+  2. Assume the remote OCI registry contains a single chart `"podinfo"` with version `"6.1.5"`
+  3. ORAS go library will return repository list `["gfichtenholt/helm-charts/podinfo"]`
+  4. kubeapps flux plugin will call `RegistryClient.Tags()` with respect to OCI reference `"ghcr.io/gfichtenholt/helm-charts/podinfo"` which will return `["6.1.5"]`
+  5. kubeapps flux plugin will call `RegistryClient.DownloadChart()` with respect to a chart with version `"6.1.5"` a URL `"ghcr.io/gfichtenholt/helm-charts/podinfo:6.1.5"`. Here, the identifier `"podinfo"` refers **BOTH to repository basename AND the chart name!**
+---

cmd/kubeapps-apis/plugins/fluxv2/packages/v1alpha1/cache/rate_limiting_queue.go

@@ -273,6 +273,26 @@ func (q *Type) ShuttingDown() bool {
 	return q.shuttingDown
 }
 
+// ShutDownWithDrain will cause q to ignore all new items added to it. As soon
+// as the worker goroutines have "drained", i.e: finished processing and called
+// Done on all existing items in the queue; they will be instructed to exit and
+// ShutDownWithDrain will return. Hence: a strict requirement for using this is;
+// your workers must ensure that Done is called on all items in the queue once
+// the shut down has been initiated, if that is not the case: this will block
+// indefinitely. It is, however, safe to call ShutDown after having called
+// ShutDownWithDrain, as to force the queue shut down to terminate immediately
+// without waiting for the drainage.
+//
+// TODO (gfichtenholt) put a stub in here just so kubeapps can upgrade to
+// k8s.io/client-go >= 0.23.X
+// ref https://github.com/vmware-tanzu/kubeapps/pull/5123#issuecomment-1194756900
+// I will implement once we upgrade k8s.io/client-go as stated and I can test the scenario
+func (q *Type) ShutDownWithDrain() {
+	// ref impl https://github.com/kubernetes/client-go/blob/b5c7588f8a17459d6f9c7a8dc24daecd2c35c98e/util/workqueue/queue.go#L211
+
+	log.Fatalf("func ShutDownWithDrain(%s) has not been implemented yet", q.name)
+}
+
 // expectAdd marks item as expected to be processed in the near future
 // Used in unit tests only
 func (q *Type) expectAdd(item string) {

cmd/kubeapps-apis/plugins/fluxv2/packages/v1alpha1/chart.go

@@ -92,16 +92,16 @@ func (s *Server) availableChartDetail(ctx context.Context, packageRef *corev1.Av
 
 		var fn cache.DownloadChartFn
 		if chartModel.Repo.Type == "oci" {
-			if ociRegistry, err := s.newOCIRegistryAndLoginWithRepo(ctx, repoName); err != nil {
+			if ociRepo, err := s.newOCIChartRepositoryAndLogin(ctx, repoName); err != nil {
 				return nil, err
 			} else {
-				fn = downloadOCIChartFn(ociRegistry)
+				fn = downloadOCIChartFn(ociRepo)
 			}
 		} else {
 			if opts, err := s.httpClientOptionsForRepo(ctx, repoName); err != nil {
 				return nil, err
 			} else {
-				fn = downloadChartViaHttpFn(opts)
+				fn = downloadHttpChartFn(opts)
 			}
 		}
 		if byteArray, err = s.chartCache.GetForOne(key, chartModel, fn); err != nil {
@@ -309,7 +309,7 @@ func availablePackageDetailFromChartDetail(chartID string, chartDetail map[strin
 	return pkg, nil
 }
 
-func downloadChartViaHttpFn(options *common.HttpClientOptions) func(chartID, chartUrl, chartVersion string) ([]byte, error) {
+func downloadHttpChartFn(options *common.HttpClientOptions) func(chartID, chartUrl, chartVersion string) ([]byte, error) {
 	return func(chartID, chartUrl, chartVersion string) ([]byte, error) {
 		client, headers, err := common.NewHttpClientAndHeaders(options)
 		if err != nil {

cmd/kubeapps-apis/plugins/fluxv2/packages/v1alpha1/chart_integration_test.go

@@ -569,6 +569,10 @@ func TestKindClusterAvailablePackageEndpointsForOCI(t *testing.T) {
 		},
 		// TODO (gfichtenholt) TLS secret with CA
 		// TODO (gfichtenholt) TLS secret with CA, pub, priv
+		// TODO (gfichtenholt) OCI repo with multiple packages/charts,
+		//      e.g. podinfo/podinfo and podinfo/foo
+		//      flux supports this, but ghcr.io does not (see comment in kind-cluster-setup.sh)
+		//      so I need somewhere to host it
 
 		/*
 			{
@@ -705,7 +709,7 @@ func TestKindClusterAvailablePackageEndpointsForOCI(t *testing.T) {
 						},
 						Identifier: repoName.Name + "/podinfo",
 					},
-					PkgVersion: "6.1.5",
+					PkgVersion: "6.1.6",
 				})
 			if err != nil {
 				t.Fatal(err)