Add HTTP 410 (Gone) status code checks to reflector and relist with RV=''

Author: jpbetz

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

@@ -201,6 +201,7 @@ 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/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.
@@ -208,19 +211,16 @@ 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 on the 2nd page or later,
-			// but still my return an "Expired" error if the 1st page fails with "Expired" or the full list fails with "Expired".
+
 			list, err = pager.List(context.Background(), options)
-			if apierrs.IsResourceExpired(err) {
-				// For Kubernetes 1.16 and earlier, if the watch cache is disabled for a resource, list requests
-				// with LastSyncResourceVersion set to a non-zero ResourceVersion will fail if the exact ResourceVersion
-				// requested is expired (e.g. an etcd compaction has remove it).
-				// To prevent the reflector from getting stuck retrying a list for an expired resource version in this
-				// case, we set ResourceVersion="" and list again to re-establish reflector to the latest available
-				// ResourceVersion, using a consistent read from etcd. This is also safe to do if watch cache is enabled
-				// and the list request returned a "Expired" error.
-				options = metav1.ListOptions{ResourceVersion: ""}
-				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)
 		}()
@@ -234,6 +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 {
@@ -307,10 +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))
@@ -329,7 +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)
@@ -442,16 +447,41 @@ func (r *Reflector) setLastSyncResourceVersion(v string) {
 	r.lastSyncResourceVersion = v
 }
 
-// relistResourceVersion is the resource version the reflector should list or relist from.
+// 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 {
-	lastSyncRV := r.LastSyncResourceVersion()
-	if lastSyncRV == "" {
-		// Explicitly set resource version to have it list from cache for
-		// performance reasons.
-		// It's fine for the returned state to be stale (we will catch up via Watch()
-		// eventually), but we need to be at least as new as the last resource version we
-		// synced to avoid going back in time.
+	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 lastSyncRV
+	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)
 }