[SANDBOX-1788] refactor the resource cache out of the OwnerFetcher

pkg/client/resource_cache.go

@@ -0,0 +1,110 @@
+package client
+
+import (
+	"fmt"
+	"sync"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/discovery"
+)
+
+type ResourceCache struct {
+	mutex           sync.Mutex                // guard the initialization ofthe resourceLists
+	resourceLists   []*metav1.APIResourceList // All available API in the cluster
+	discoveryClient discovery.ServerResourcesInterface
+}
+
+// NewResourceCache creates a new ResourceCache  with the provided discovery client.
+// The discovery client is used to fetch available API resources.
+func NewResourceCache(discoveryClient discovery.ServerResourcesInterface) *ResourceCache {
+	return &ResourceCache{
+		discoveryClient: discoveryClient,
+	}
+}
+
+// GVRForKind returns a group-resource-version for the supplied kind and api version.
+func (rc *ResourceCache) GVRForKind(kind, apiVersion string) (gvr schema.GroupVersionResource, found bool, namespaced bool, err error) {
+	if err = rc.ensureResourceList(); err != nil {
+		return
+	}
+
+	// Parse the group and version from the APIVersion (e.g., "apps/v1" -> group: "apps", version: "v1")
+	var gv schema.GroupVersion
+	gv, err = schema.ParseGroupVersion(apiVersion)
+	if err != nil {
+		err = fmt.Errorf("failed to parse APIVersion %s: %w", apiVersion, err)
+		return
+	}
+
+	// Look for a matching resource
+	for _, resourceList := range rc.resourceLists {
+		if resourceList.GroupVersion == apiVersion {
+			for _, apiResource := range resourceList.APIResources {
+				if apiResource.Kind == kind {
+					// Construct the GVR
+					found = true
+					gvr = schema.GroupVersionResource{
+						Group:    gv.Group,
+						Version:  gv.Version,
+						Resource: apiResource.Name,
+					}
+					namespaced = apiResource.Namespaced
+
+					return
+				}
+			}
+		}
+	}
+
+	return
+}
+
+// GVKForGR given the group-resource, returns the first matching GVK for it.
+func (rc *ResourceCache) GVKForGR(gr schema.GroupResource) (gvk schema.GroupVersionKind, found bool, err error) {
+	if err = rc.ensureResourceList(); err != nil {
+		return
+	}
+
+	for _, resourceList := range rc.resourceLists {
+		var gv schema.GroupVersion
+		gv, err = schema.ParseGroupVersion(resourceList.GroupVersion)
+		if err != nil {
+			err = fmt.Errorf("failed to parse GroupVersion %s: %w", resourceList.GroupVersion, err)
+			return
+		}
+		if gv.Group != gr.Group {
+			continue
+		}
+		for _, res := range resourceList.APIResources {
+			if res.Name == gr.Resource {
+				gvk = schema.GroupVersionKind{Group: gv.Group, Version: gv.Version, Kind: res.Kind}
+				found = true
+				return
+			}
+		}
+	}
+
+	return
+}
+
+func (rc *ResourceCache) ensureResourceList() error {
+	rc.mutex.Lock()
+	defer rc.mutex.Unlock()
+
+	if rc.resourceLists == nil {
+		// Get all API resources from the cluster using the discovery client. We need it for constructing GVRs for unstructured objects.
+		// Do it here once, so we do not have to list it multiple times before listing/getting every unstructured resource.
+		//
+		// The ServerPreferredResources() method is meant to return partial results on failure.
+		// We ignore them here for the sake of simplicity. Let's just retry to get the full results the next time.
+		resourceList, err := rc.discoveryClient.ServerPreferredResources()
+		if err != nil {
+			return err
+		}
+
+		rc.resourceLists = resourceList
+	}
+
+	return nil
+}

pkg/client/resource_cache_test.go

@@ -0,0 +1,241 @@
+package client
+
+import (
+	"errors"
+	"fmt"
+	"sync/atomic"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+)
+
+type fakeDiscoveryClient struct {
+	resources []*metav1.APIResourceList
+	err       error
+	calls     atomic.Int32
+}
+
+func (f *fakeDiscoveryClient) ServerResourcesForGroupVersion(string) (*metav1.APIResourceList, error) {
+	return nil, nil
+}
+
+func (f *fakeDiscoveryClient) ServerGroupsAndResources() ([]*metav1.APIGroup, []*metav1.APIResourceList, error) {
+	return nil, nil, nil
+}
+
+func (f *fakeDiscoveryClient) ServerPreferredResources() ([]*metav1.APIResourceList, error) {
+	f.calls.Add(1)
+	return f.resources, f.err
+}
+
+func (f *fakeDiscoveryClient) ServerPreferredNamespacedResources() ([]*metav1.APIResourceList, error) {
+	return nil, nil
+}
+
+func TestGVRForKind(t *testing.T) {
+	resources := []*metav1.APIResourceList{
+		{
+			GroupVersion: "v1",
+			APIResources: []metav1.APIResource{
+				{Name: "pods", Kind: "Pod", Namespaced: true},
+				{Name: "nodes", Kind: "Node", Namespaced: false},
+			},
+		},
+		{
+			GroupVersion: "apps/v1",
+			APIResources: []metav1.APIResource{
+				{Name: "deployments", Kind: "Deployment", Namespaced: true},
+				{Name: "daemonsets", Kind: "DaemonSet", Namespaced: true},
+			},
+		},
+	}
+
+	t.Run("finds namespaced core resource", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		gvr, found, namespaced, err := rc.GVRForKind("Pod", "v1")
+
+		require.NoError(t, err)
+		assert.True(t, found)
+		assert.True(t, namespaced)
+		assert.Equal(t, schema.GroupVersionResource{Group: "", Version: "v1", Resource: "pods"}, gvr)
+	})
+
+	t.Run("finds cluster-scoped core resource", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		gvr, found, namespaced, err := rc.GVRForKind("Node", "v1")
+
+		require.NoError(t, err)
+		assert.True(t, found)
+		assert.False(t, namespaced)
+		assert.Equal(t, schema.GroupVersionResource{Group: "", Version: "v1", Resource: "nodes"}, gvr)
+	})
+
+	t.Run("finds resource in non-core group", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		gvr, found, namespaced, err := rc.GVRForKind("Deployment", "apps/v1")
+
+		require.NoError(t, err)
+		assert.True(t, found)
+		assert.True(t, namespaced)
+		assert.Equal(t, schema.GroupVersionResource{Group: "apps", Version: "v1", Resource: "deployments"}, gvr)
+	})
+
+	t.Run("not found", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		_, found, _, err := rc.GVRForKind("StatefulSet", "apps/v1")
+
+		require.NoError(t, err)
+		assert.False(t, found)
+		assert.NoError(t, err)
+	})
+
+	t.Run("not found in wrong api version", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		_, found, _, err := rc.GVRForKind("Deployment", "apps/v1beta1")
+
+		require.NoError(t, err)
+		assert.False(t, found)
+		assert.NoError(t, err)
+	})
+
+	t.Run("invalid api version", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		_, _, _, err := rc.GVRForKind("Pod", "a/b/c")
+
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "failed to parse APIVersion")
+	})
+
+	t.Run("discovery error", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{err: errors.New("discovery failed")})
+
+		_, _, _, err := rc.GVRForKind("Pod", "v1")
+
+		require.EqualError(t, err, "discovery failed")
+	})
+
+	t.Run("caches discovery results", func(t *testing.T) {
+		dc := &fakeDiscoveryClient{resources: resources}
+		rc := NewResourceCache(dc)
+
+		_, _, _, err := rc.GVRForKind("Pod", "v1")
+		require.NoError(t, err)
+
+		_, _, _, err = rc.GVRForKind("Deployment", "apps/v1")
+		require.NoError(t, err)
+
+		assert.Equal(t, int32(1), dc.calls.Load(), "discovery should have been called only once")
+	})
+}
+
+func TestGVKForGR(t *testing.T) {
+	resources := []*metav1.APIResourceList{
+		{
+			GroupVersion: "v1",
+			APIResources: []metav1.APIResource{
+				{Name: "pods", Kind: "Pod", Namespaced: true},
+				{Name: "services", Kind: "Service", Namespaced: true},
+			},
+		},
+		{
+			GroupVersion: "apps/v1",
+			APIResources: []metav1.APIResource{
+				{Name: "deployments", Kind: "Deployment", Namespaced: true},
+				{Name: "replicasets", Kind: "ReplicaSet", Namespaced: true},
+			},
+		},
+		{
+			GroupVersion: "kubevirt.io/v1",
+			APIResources: []metav1.APIResource{
+				{Name: "virtualmachines", Kind: "VirtualMachine", Namespaced: true},
+			},
+		},
+	}
+
+	t.Run("finds core group resource", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		gvk, found, err := rc.GVKForGR(schema.GroupResource{Group: "", Resource: "pods"})
+
+		require.NoError(t, err)
+		assert.True(t, found)
+		assert.Equal(t, schema.GroupVersionKind{Group: "", Version: "v1", Kind: "Pod"}, gvk)
+	})
+
+	t.Run("finds non-core group resource", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		gvk, found, err := rc.GVKForGR(schema.GroupResource{Group: "apps", Resource: "deployments"})
+
+		require.NoError(t, err)
+		assert.True(t, found)
+		assert.Equal(t, schema.GroupVersionKind{Group: "apps", Version: "v1", Kind: "Deployment"}, gvk)
+	})
+
+	t.Run("finds resource with dotted group", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		gvk, found, err := rc.GVKForGR(schema.GroupResource{Group: "kubevirt.io", Resource: "virtualmachines"})
+
+		require.NoError(t, err)
+		assert.True(t, found)
+		assert.Equal(t, schema.GroupVersionKind{Group: "kubevirt.io", Version: "v1", Kind: "VirtualMachine"}, gvk)
+	})
+
+	t.Run("not found", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		_, found, err := rc.GVKForGR(schema.GroupResource{Group: "apps", Resource: "statefulsets"})
+
+		require.NoError(t, err)
+		assert.False(t, found)
+		assert.NoError(t, err)
+	})
+
+	t.Run("wrong group", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{resources: resources})
+
+		_, found, err := rc.GVKForGR(schema.GroupResource{Group: "extensions", Resource: "deployments"})
+
+		require.NoError(t, err)
+		assert.False(t, found)
+		assert.NoError(t, err)
+	})
+
+	t.Run("discovery error", func(t *testing.T) {
+		rc := NewResourceCache(&fakeDiscoveryClient{err: errors.New("discovery failed")})
+
+		_, _, err := rc.GVKForGR(schema.GroupResource{Group: "apps", Resource: "deployments"})
+
+		require.EqualError(t, err, "discovery failed")
+	})
+}
+
+func TestThreadSafety(t *testing.T) {
+	// given
+	cl := &fakeDiscoveryClient{resources: []*metav1.APIResourceList{}}
+	rc := NewResourceCache(cl)
+
+	// when
+	t.Run("wrap", func(t *testing.T) { // wrap so that the parallel inner tests complete before we check in the then.
+		for i := range 20 {
+			t.Run(fmt.Sprintf("concurrent-%d", i), func(t *testing.T) {
+				t.Parallel()
+				_, _, _, err := rc.GVRForKind("SomeKind", "v1")
+				assert.NoError(t, err)
+			})
+		}
+	})
+
+	// then
+	assert.Equal(t, int32(1), cl.calls.Load())
+}