Merge pull request kubernetes#83520 from jpbetz/reflector-relist-rv

Avoid going back in time in Reflector relist (revived)

Author: k8s-ci-robot

staging/src/k8s.io/apimachinery/pkg/api/errors/errors.go

@@ -223,6 +223,7 @@ func NewApplyConflict(causes []metav1.StatusCause, message string) *StatusError
 }
 
 // NewGone returns an error indicating the item no longer available at the server and no forwarding address is known.
+// DEPRECATED: Please use NewResourceExpired instead.
 func NewGone(message string) *StatusError {
 	return &StatusError{metav1.Status{
 		Status:  metav1.StatusFailure,

staging/src/k8s.io/apiserver/pkg/storage/cacher/watch_cache.go

@@ -468,7 +468,7 @@ func (w *watchCache) GetAllEventsSinceThreadUnsafe(resourceVersion uint64) ([]*w
 		return result, nil
 	}
 	if resourceVersion < oldest-1 {
-		return nil, errors.NewGone(fmt.Sprintf("too old resource version: %d (%d)", resourceVersion, oldest-1))
+		return nil, errors.NewResourceExpired(fmt.Sprintf("too old resource version: %d (%d)", resourceVersion, oldest-1))
 	}
 
 	// Binary search the smallest index at which resourceVersion is greater than the given one.

staging/src/k8s.io/apiserver/pkg/storage/tests/cacher_test.go

@@ -444,8 +444,8 @@ func TestWatch(t *testing.T) {
 	}
 	defer tooOldWatcher.Stop()
 	// Ensure we get a "Gone" error
-	expectedGoneError := errors.NewGone("").ErrStatus
-	verifyWatchEvent(t, tooOldWatcher, watch.Error, &expectedGoneError)
+	expectedResourceExpiredError := errors.NewResourceExpired("").ErrStatus
+	verifyWatchEvent(t, tooOldWatcher, watch.Error, &expectedResourceExpiredError)
 
 	initialWatcher, err := cacher.Watch(context.TODO(), "pods/ns/foo", fooCreated.ResourceVersion, storage.Everything)
 	if err != nil {
@@ -668,8 +668,8 @@ func TestEmptyWatchEventCache(t *testing.T) {
 			t.Fatalf("Unexpected error: %v", err)
 		}
 		defer watcher.Stop()
-		expectedGoneError := errors.NewGone("").ErrStatus
-		verifyWatchEvent(t, watcher, watch.Error, &expectedGoneError)
+		expectedResourceExpiredError := errors.NewResourceExpired("").ErrStatus
+		verifyWatchEvent(t, watcher, watch.Error, &expectedResourceExpiredError)
 	}
 
 	{

staging/src/k8s.io/client-go/tools/cache/BUILD

@@ -27,6 +27,7 @@ go_test(
     race = "off",
     deps = [
         "//staging/src/k8s.io/api/core/v1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/api/errors:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/api/meta:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured:go_default_library",

staging/src/k8s.io/client-go/tools/cache/reflector.go

@@ -74,6 +74,9 @@ type Reflector struct {
 	// observed when doing a sync with the underlying store
 	// it is thread safe, but not synchronized with the underlying store
 	lastSyncResourceVersion string
+	// isLastSyncResourceVersionGone is true if the previous list or watch request with lastSyncResourceVersion
+	// failed with an HTTP 410 (Gone) status code.
+	isLastSyncResourceVersionGone bool
 	// lastSyncResourceVersionMutex guards read/write access to lastSyncResourceVersion
 	lastSyncResourceVersionMutex sync.RWMutex
 	// WatchListPageSize is the requested chunk size of initial and resync watch lists.
@@ -185,10 +188,7 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 	klog.V(3).Infof("Listing and watching %v from %s", r.expectedTypeName, r.name)
 	var resourceVersion string
 
-	// Explicitly set "0" as resource version - it's fine for the List()
-	// to be served from cache and potentially be delayed relative to
-	// etcd contents. Reflector framework will catch up via Watch() eventually.
-	options := metav1.ListOptions{ResourceVersion: "0"}
+	options := metav1.ListOptions{ResourceVersion: r.relistResourceVersion()}
 
 	if err := func() error {
 		initTrace := trace.New("Reflector ListAndWatch", trace.Field{"name", r.name})
@@ -211,8 +211,17 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 			if r.WatchListPageSize != 0 {
 				pager.PageSize = r.WatchListPageSize
 			}
-			// Pager falls back to full list if paginated list calls fail due to an "Expired" error.
+
 			list, err = pager.List(context.Background(), options)
+			if isExpiredError(err) {
+				r.setIsLastSyncResourceVersionExpired(true)
+				// Retry immediately if the resource version used to list is expired.
+				// The pager already falls back to full list if paginated list calls fail due to an "Expired" error on
+				// continuation pages, but the pager might not be enabled, or the full list might fail because the
+				// resource version it is listing at is expired, so we need to fallback to resourceVersion="" in all
+				// to recover and ensure the reflector makes forward progress.
+				list, err = pager.List(context.Background(), metav1.ListOptions{ResourceVersion: r.relistResourceVersion()})
+			}
 			close(listCh)
 		}()
 		select {
@@ -225,6 +234,7 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 		if err != nil {
 			return fmt.Errorf("%s: Failed to list %v: %v", r.name, r.expectedTypeName, err)
 		}
+		r.setIsLastSyncResourceVersionExpired(false) // list was successful
 		initTrace.Step("Objects listed")
 		listMetaInterface, err := meta.ListAccessor(list)
 		if err != nil {
@@ -298,10 +308,13 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 
 		w, err := r.listerWatcher.Watch(options)
 		if err != nil {
-			switch err {
-			case io.EOF:
+			switch {
+			case isExpiredError(err):
+				r.setIsLastSyncResourceVersionExpired(true)
+				klog.V(4).Infof("%s: watch of %v closed with: %v", r.name, r.expectedTypeName, err)
+			case err == io.EOF:
 				// watch closed normally
-			case io.ErrUnexpectedEOF:
+			case err == io.ErrUnexpectedEOF:
 				klog.V(1).Infof("%s: Watch for %v closed with unexpected EOF: %v", r.name, r.expectedTypeName, err)
 			default:
 				utilruntime.HandleError(fmt.Errorf("%s: Failed to watch %v: %v", r.name, r.expectedTypeName, err))
@@ -320,7 +333,8 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 		if err := r.watchHandler(w, &resourceVersion, resyncerrc, stopCh); err != nil {
 			if err != errorStopRequested {
 				switch {
-				case apierrs.IsResourceExpired(err):
+				case isExpiredError(err):
+					r.setIsLastSyncResourceVersionExpired(true)
 					klog.V(4).Infof("%s: watch of %v ended with: %v", r.name, r.expectedTypeName, err)
 				default:
 					klog.Warningf("%s: watch of %v ended with: %v", r.name, r.expectedTypeName, err)
@@ -432,3 +446,42 @@ func (r *Reflector) setLastSyncResourceVersion(v string) {
 	defer r.lastSyncResourceVersionMutex.Unlock()
 	r.lastSyncResourceVersion = v
 }
+
+// relistResourceVersion determines the resource version the reflector should list or relist from.
+// Returns either the lastSyncResourceVersion so that this reflector will relist with a resource
+// versions no older than has already been observed in relist results or watch events, or, if the last relist resulted
+// in an HTTP 410 (Gone) status code, returns "" so that the relist will use the latest resource version available in
+// etcd via a quorum read.
+func (r *Reflector) relistResourceVersion() string {
+	r.lastSyncResourceVersionMutex.RLock()
+	defer r.lastSyncResourceVersionMutex.RUnlock()
+
+	if r.isLastSyncResourceVersionGone {
+		// Since this reflector makes paginated list requests, and all paginated list requests skip the watch cache
+		// if the lastSyncResourceVersion is expired, we set ResourceVersion="" and list again to re-establish reflector
+		// to the latest available ResourceVersion, using a consistent read from etcd.
+		return ""
+	}
+	if r.lastSyncResourceVersion == "" {
+		// For performance reasons, initial list performed by reflector uses "0" as resource version to allow it to
+		// be served from the watch cache if it is enabled.
+		return "0"
+	}
+	return r.lastSyncResourceVersion
+}
+
+// setIsLastSyncResourceVersionExpired sets if the last list or watch request with lastSyncResourceVersion returned a
+// expired error: HTTP 410 (Gone) Status Code.
+func (r *Reflector) setIsLastSyncResourceVersionExpired(isExpired bool) {
+	r.lastSyncResourceVersionMutex.Lock()
+	defer r.lastSyncResourceVersionMutex.Unlock()
+	r.isLastSyncResourceVersionGone = isExpired
+}
+
+func isExpiredError(err error) bool {
+	// In Kubernetes 1.17 and earlier, the api server returns both apierrs.StatusReasonExpired and
+	// apierrs.StatusReasonGone for HTTP 410 (Gone) status code responses. In 1.18 the kube server is more consistent
+	// and always returns apierrs.StatusReasonExpired. For backward compatibility we can only remove the apierrs.IsGone
+	// check when we fully drop support for Kubernetes 1.17 servers from reflectors.
+	return apierrs.IsResourceExpired(err) || apierrs.IsGone(err)
+}

staging/src/k8s.io/client-go/tools/cache/reflector_test.go

@@ -26,6 +26,7 @@ import (
 	"time"
 
 	"k8s.io/api/core/v1"
+	apierrs "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -434,6 +435,194 @@ func TestReflectorWatchListPageSize(t *testing.T) {
 	}
 }
 
+// TestReflectorResyncWithResourceVersion ensures that a reflector keeps track of the ResourceVersion and sends
+// it in relist requests to prevent the reflector from traveling back in time if the relist is to a api-server or
+// etcd that is partitioned and serving older data than the reflector has already processed.
+func TestReflectorResyncWithResourceVersion(t *testing.T) {
+	stopCh := make(chan struct{})
+	s := NewStore(MetaNamespaceKeyFunc)
+	listCallRVs := []string{}
+
+	lw := &testLW{
+		WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+			// Stop once the reflector begins watching since we're only interested in the list.
+			close(stopCh)
+			fw := watch.NewFake()
+			return fw, nil
+		},
+		ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+			listCallRVs = append(listCallRVs, options.ResourceVersion)
+			pods := make([]v1.Pod, 8)
+			for i := 0; i < 8; i++ {
+				pods[i] = v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: fmt.Sprintf("pod-%d", i), ResourceVersion: fmt.Sprintf("%d", i)}}
+			}
+			switch options.ResourceVersion {
+			case "0":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "10"}, Items: pods[0:4]}, nil
+			case "10":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "11"}, Items: pods[0:8]}, nil
+			default:
+				t.Fatalf("Unrecognized ResourceVersion: %s", options.ResourceVersion)
+			}
+			return nil, nil
+		},
+	}
+	r := NewReflector(lw, &v1.Pod{}, s, 0)
+
+	// Initial list should use RV=0
+	r.ListAndWatch(stopCh)
+
+	results := s.List()
+	if len(results) != 4 {
+		t.Errorf("Expected 4 results, got %d", len(results))
+	}
+
+	// relist should use lastSyncResourceVersions (RV=10)
+	stopCh = make(chan struct{})
+	r.ListAndWatch(stopCh)
+
+	results = s.List()
+	if len(results) != 8 {
+		t.Errorf("Expected 8 results, got %d", len(results))
+	}
+
+	expectedRVs := []string{"0", "10"}
+	if !reflect.DeepEqual(listCallRVs, expectedRVs) {
+		t.Errorf("Expected series of list calls with resource versiosn of %v but got: %v", expectedRVs, listCallRVs)
+	}
+}
+
+// TestReflectorExpiredExactResourceVersion tests that a reflector handles the behavior of kubernetes 1.16 an earlier
+// where if the exact ResourceVersion requested is not available for a List request for a non-zero ResourceVersion,
+// an "Expired" error is returned if the ResourceVersion has expired (etcd has compacted it).
+// (In kubernetes 1.17, or when the watch cache is enabled, the List will instead return the list that is no older than
+// the requested ResourceVersion).
+func TestReflectorExpiredExactResourceVersion(t *testing.T) {
+	stopCh := make(chan struct{})
+	s := NewStore(MetaNamespaceKeyFunc)
+	listCallRVs := []string{}
+
+	lw := &testLW{
+		WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+			// Stop once the reflector begins watching since we're only interested in the list.
+			close(stopCh)
+			fw := watch.NewFake()
+			return fw, nil
+		},
+		ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+			listCallRVs = append(listCallRVs, options.ResourceVersion)
+			pods := make([]v1.Pod, 8)
+			for i := 0; i < 8; i++ {
+				pods[i] = v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: fmt.Sprintf("pod-%d", i), ResourceVersion: fmt.Sprintf("%d", i)}}
+			}
+			switch options.ResourceVersion {
+			case "0":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "10"}, Items: pods[0:4]}, nil
+			case "10":
+				// When watch cache is disabled, if the exact ResourceVersion requested is not available, a "Expired" error is returned.
+				return nil, apierrs.NewResourceExpired("The resourceVersion for the provided watch is too old.")
+			case "":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "11"}, Items: pods[0:8]}, nil
+			default:
+				t.Fatalf("Unrecognized ResourceVersion: %s", options.ResourceVersion)
+			}
+			return nil, nil
+		},
+	}
+	r := NewReflector(lw, &v1.Pod{}, s, 0)
+
+	// Initial list should use RV=0
+	r.ListAndWatch(stopCh)
+
+	results := s.List()
+	if len(results) != 4 {
+		t.Errorf("Expected 4 results, got %d", len(results))
+	}
+
+	// relist should use lastSyncResourceVersions (RV=10) and since RV=10 is expired, it should retry with RV="".
+	stopCh = make(chan struct{})
+	r.ListAndWatch(stopCh)
+
+	results = s.List()
+	if len(results) != 8 {
+		t.Errorf("Expected 8 results, got %d", len(results))
+	}
+
+	expectedRVs := []string{"0", "10", ""}
+	if !reflect.DeepEqual(listCallRVs, expectedRVs) {
+		t.Errorf("Expected series of list calls with resource versiosn of %v but got: %v", expectedRVs, listCallRVs)
+	}
+}
+
+func TestReflectorFullListIfExpired(t *testing.T) {
+	stopCh := make(chan struct{})
+	s := NewStore(MetaNamespaceKeyFunc)
+	listCallRVs := []string{}
+
+	lw := &testLW{
+		WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+			// Stop once the reflector begins watching since we're only interested in the list.
+			close(stopCh)
+			fw := watch.NewFake()
+			return fw, nil
+		},
+		ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+			listCallRVs = append(listCallRVs, options.ResourceVersion)
+			pods := make([]v1.Pod, 8)
+			for i := 0; i < 8; i++ {
+				pods[i] = v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: fmt.Sprintf("pod-%d", i), ResourceVersion: fmt.Sprintf("%d", i)}}
+			}
+			switch options.ResourceVersion {
+			case "0":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "10"}, Items: pods[0:4]}, nil
+			case "10":
+				switch options.Limit {
+				case 4:
+					switch options.Continue {
+					case "":
+						return &v1.PodList{ListMeta: metav1.ListMeta{Continue: "C1", ResourceVersion: "11"}, Items: pods[0:4]}, nil
+					case "C1":
+						return nil, apierrs.NewResourceExpired("The resourceVersion for the provided watch is too old.")
+					default:
+						t.Fatalf("Unrecognized Continue: %s", options.Continue)
+					}
+				case 0:
+					return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "11"}, Items: pods[0:8]}, nil
+				default:
+					t.Fatalf("Unrecognized Limit: %d", options.Limit)
+				}
+			default:
+				t.Fatalf("Unrecognized ResourceVersion: %s", options.ResourceVersion)
+			}
+			return nil, nil
+		},
+	}
+	r := NewReflector(lw, &v1.Pod{}, s, 0)
+	r.WatchListPageSize = 4
+
+	// Initial list should use RV=0
+	r.ListAndWatch(stopCh)
+
+	results := s.List()
+	if len(results) != 4 {
+		t.Errorf("Expected 4 results, got %d", len(results))
+	}
+
+	// relist should use lastSyncResourceVersions (RV=10) and since second page of RV=10 is expired, it should full list with RV=10
+	stopCh = make(chan struct{})
+	r.ListAndWatch(stopCh)
+
+	results = s.List()
+	if len(results) != 8 {
+		t.Errorf("Expected 8 results, got %d", len(results))
+	}
+
+	expectedRVs := []string{"0", "10", "10", "10"}
+	if !reflect.DeepEqual(listCallRVs, expectedRVs) {
+		t.Errorf("Expected series of list calls with resource versiosn of %v but got: %v", expectedRVs, listCallRVs)
+	}
+}
+
 func TestReflectorSetExpectedType(t *testing.T) {
 	obj := &unstructured.Unstructured{}
 	gvk := schema.GroupVersionKind{

staging/src/k8s.io/client-go/tools/pager/pager.go

@@ -87,7 +87,11 @@ func (p *ListPager) List(ctx context.Context, options metav1.ListOptions) (runti
 
 		obj, err := p.PageFn(ctx, options)
 		if err != nil {
-			if !errors.IsResourceExpired(err) || !p.FullListIfExpired {
+			// Only fallback to full list if an "Expired" errors is returned, FullListIfExpired is true, and
+			// the "Expired" error occurred in page 2 or later (since full list is intended to prevent a pager.List from
+			// failing when the resource versions is established by the first page request falls out of the compaction
+			// during the subsequent list requests).
+			if !errors.IsResourceExpired(err) || !p.FullListIfExpired || options.Continue == "" {
 				return nil, err
 			}
 			// the list expired while we were processing, fall back to a full list