Merge pull request #55259 from ironcladlou/gc-partial-discovery

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Tolerate partial discovery in garbage collector

Allow the garbage collector to tolerate partial discovery failures. On a
partial failure, use whatever was discovered, log the failures, and
allow the resync logic to try again later.

Fixes #55022.

```release-note
API discovery failures no longer crash the kube controller manager via the garbage collector.
```

/cc @caesarxuchao

cmd/kube-controller-manager/app/core.go

@@ -348,10 +348,7 @@ func startGarbageCollectorController(ctx ControllerContext) (bool, error) {
 	clientPool := dynamic.NewClientPool(config, restMapper, dynamic.LegacyAPIPathResolverFunc)
 
 	// Get an initial set of deletable resources to prime the garbage collector.
-	deletableResources, err := garbagecollector.GetDeletableResources(discoveryClient)
-	if err != nil {
-		return true, err
-	}
+	deletableResources := garbagecollector.GetDeletableResources(discoveryClient)
 	ignoredResources := make(map[schema.GroupResource]struct{})
 	for _, r := range ctx.Options.GCIgnoredResources {
 		ignoredResources[schema.GroupResource{Group: r.Group, Resource: r.Resource}] = struct{}{}

pkg/controller/garbagecollector/BUILD

@@ -66,6 +66,7 @@ go_test(
         "//vendor/k8s.io/apimachinery/pkg/util/json:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/strategicpatch:go_default_library",
+        "//vendor/k8s.io/client-go/discovery:go_default_library",
         "//vendor/k8s.io/client-go/dynamic:go_default_library",
         "//vendor/k8s.io/client-go/informers:go_default_library",
         "//vendor/k8s.io/client-go/kubernetes/fake:go_default_library",

pkg/controller/garbagecollector/garbagecollector.go

@@ -171,11 +171,7 @@ func (gc *GarbageCollector) Sync(discoveryClient discovery.DiscoveryInterface, p
 	oldResources := make(map[schema.GroupVersionResource]struct{})
 	wait.Until(func() {
 		// Get the current resource list from discovery.
-		newResources, err := GetDeletableResources(discoveryClient)
-		if err != nil {
-			utilruntime.HandleError(err)
-			return
-		}
+		newResources := GetDeletableResources(discoveryClient)
 
 		// Detect first or abnormal sync and try again later.
 		if oldResources == nil || len(oldResources) == 0 {
@@ -592,15 +588,37 @@ func (gc *GarbageCollector) GraphHasUID(UIDs []types.UID) bool {
 // GetDeletableResources returns all resources from discoveryClient that the
 // garbage collector should recognize and work with. More specifically, all
 // preferred resources which support the 'delete' verb.
-func GetDeletableResources(discoveryClient discovery.DiscoveryInterface) (map[schema.GroupVersionResource]struct{}, error) {
+//
+// All discovery errors are considered temporary. Upon encountering any error,
+// GetDeletableResources will log and return any discovered resources it was
+// able to process (which may be none).
+func GetDeletableResources(discoveryClient discovery.ServerResourcesInterface) map[schema.GroupVersionResource]struct{} {
 	preferredResources, err := discoveryClient.ServerPreferredResources()
 	if err != nil {
-		return nil, fmt.Errorf("failed to get supported resources from server: %v", err)
+		if discovery.IsGroupDiscoveryFailedError(err) {
+			glog.Warning("failed to discover some groups: %v", err.(*discovery.ErrGroupDiscoveryFailed).Groups)
+		} else {
+			glog.Warning("failed to discover preferred resources: %v", err)
+		}
 	}
+	if preferredResources == nil {
+		return map[schema.GroupVersionResource]struct{}{}
+	}
+
+	// This is extracted from discovery.GroupVersionResources to allow tolerating
+	// failures on a per-resource basis.
 	deletableResources := discovery.FilteredBy(discovery.SupportsAllVerbs{Verbs: []string{"delete"}}, preferredResources)
-	deletableGroupVersionResources, err := discovery.GroupVersionResources(deletableResources)
-	if err != nil {
-		return nil, fmt.Errorf("Failed to parse resources from server: %v", err)
+	deletableGroupVersionResources := map[schema.GroupVersionResource]struct{}{}
+	for _, rl := range deletableResources {
+		gv, err := schema.ParseGroupVersion(rl.GroupVersion)
+		if err != nil {
+			glog.Warning("ignoring invalid discovered resource %q: %v", rl.GroupVersion, err)
+			continue
+		}
+		for i := range rl.APIResources {
+			deletableGroupVersionResources[schema.GroupVersionResource{Group: gv.Group, Version: gv.Version, Resource: rl.APIResources[i].Name}] = struct{}{}
+		}
 	}
-	return deletableGroupVersionResources, nil
+
+	return deletableGroupVersionResources
 }

pkg/controller/garbagecollector/garbagecollector_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package garbagecollector
 
 import (
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
@@ -37,6 +38,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/json"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/strategicpatch"
+	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes/fake"
@@ -671,3 +673,109 @@ func TestOrphanDependentsFailure(t *testing.T) {
 		t.Errorf("expected error contains text %s, got %v", expected, err)
 	}
 }
+
+// TestGetDeletableResources ensures GetDeletableResources always returns
+// something usable regardless of discovery output.
+func TestGetDeletableResources(t *testing.T) {
+	tests := map[string]struct {
+		serverResources    []*metav1.APIResourceList
+		err                error
+		deletableResources map[schema.GroupVersionResource]struct{}
+	}{
+		"no error": {
+			serverResources: []*metav1.APIResourceList{
+				{
+					// Valid GroupVersion
+					GroupVersion: "apps/v1",
+					APIResources: []metav1.APIResource{
+						{Name: "pods", Namespaced: true, Kind: "Pod", Verbs: metav1.Verbs{"delete"}},
+						{Name: "services", Namespaced: true, Kind: "Service"},
+					},
+				},
+				{
+					// Invalid GroupVersion, should be ignored
+					GroupVersion: "foo//whatever",
+					APIResources: []metav1.APIResource{
+						{Name: "bars", Namespaced: true, Kind: "Bar", Verbs: metav1.Verbs{"delete"}},
+					},
+				},
+			},
+			err: nil,
+			deletableResources: map[schema.GroupVersionResource]struct{}{
+				{Group: "apps", Version: "v1", Resource: "pods"}: {},
+			},
+		},
+		"nonspecific failure, includes usable results": {
+			serverResources: []*metav1.APIResourceList{
+				{
+					GroupVersion: "apps/v1",
+					APIResources: []metav1.APIResource{
+						{Name: "pods", Namespaced: true, Kind: "Pod", Verbs: metav1.Verbs{"delete"}},
+						{Name: "services", Namespaced: true, Kind: "Service"},
+					},
+				},
+			},
+			err: fmt.Errorf("internal error"),
+			deletableResources: map[schema.GroupVersionResource]struct{}{
+				{Group: "apps", Version: "v1", Resource: "pods"}: {},
+			},
+		},
+		"partial discovery failure, includes usable results": {
+			serverResources: []*metav1.APIResourceList{
+				{
+					GroupVersion: "apps/v1",
+					APIResources: []metav1.APIResource{
+						{Name: "pods", Namespaced: true, Kind: "Pod", Verbs: metav1.Verbs{"delete"}},
+						{Name: "services", Namespaced: true, Kind: "Service"},
+					},
+				},
+			},
+			err: &discovery.ErrGroupDiscoveryFailed{
+				Groups: map[schema.GroupVersion]error{
+					{Group: "foo", Version: "v1"}: fmt.Errorf("discovery failure"),
+				},
+			},
+			deletableResources: map[schema.GroupVersionResource]struct{}{
+				{Group: "apps", Version: "v1", Resource: "pods"}: {},
+			},
+		},
+		"discovery failure, no results": {
+			serverResources:    nil,
+			err:                fmt.Errorf("internal error"),
+			deletableResources: map[schema.GroupVersionResource]struct{}{},
+		},
+	}
+
+	for name, test := range tests {
+		t.Logf("testing %q", name)
+		client := &fakeServerResources{
+			PreferredResources: test.serverResources,
+			Error:              test.err,
+		}
+		actual := GetDeletableResources(client)
+		if !reflect.DeepEqual(test.deletableResources, actual) {
+			t.Errorf("expected resources:\n%v\ngot:\n%v", test.deletableResources, actual)
+		}
+	}
+}
+
+type fakeServerResources struct {
+	PreferredResources []*metav1.APIResourceList
+	Error              error
+}
+
+func (_ *fakeServerResources) ServerResourcesForGroupVersion(groupVersion string) (*metav1.APIResourceList, error) {
+	return nil, nil
+}
+
+func (_ *fakeServerResources) ServerResources() ([]*metav1.APIResourceList, error) {
+	return nil, nil
+}
+
+func (f *fakeServerResources) ServerPreferredResources() ([]*metav1.APIResourceList, error) {
+	return f.PreferredResources, f.Error
+}
+
+func (_ *fakeServerResources) ServerPreferredNamespacedResources() ([]*metav1.APIResourceList, error) {
+	return nil, nil
+}

test/integration/garbagecollector/garbage_collector_test.go

@@ -233,10 +233,7 @@ func setup(t *testing.T, workerCount int) *testContext {
 	discoveryClient := cacheddiscovery.NewMemCacheClient(clientSet.Discovery())
 	restMapper := discovery.NewDeferredDiscoveryRESTMapper(discoveryClient, meta.InterfacesForUnstructured)
 	restMapper.Reset()
-	deletableResources, err := garbagecollector.GetDeletableResources(discoveryClient)
-	if err != nil {
-		t.Fatalf("unable to get deletable resources: %v", err)
-	}
+	deletableResources := garbagecollector.GetDeletableResources(discoveryClient)
 	config := *masterConfig
 	config.ContentConfig = dynamic.ContentConfig()
 	metaOnlyClientPool := dynamic.NewClientPool(&config, restMapper, dynamic.LegacyAPIPathResolverFunc)