Merge pull request #125730 from p0lyn0mial/upstream-bring-back-consistent-read-from-cache-supports-pagination

apiserver/storage/cacher: consistent read from cache supports limit

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

@@ -615,7 +615,7 @@ func (c *Cacher) Watch(ctx context.Context, key string, opts storage.ListOptions
 	// to compute watcher.forget function (which has to happen under lock).
 	watcher := newCacheWatcher(
 		chanSize,
-		filterWithAttrsFunction(key, pred),
+		filterWithAttrsAndPrefixFunction(key, pred),
 		emptyFunc,
 		c.versioner,
 		deadline,
@@ -768,12 +768,26 @@ func shouldDelegateList(opts storage.ListOptions) bool {
 	consistentReadFromStorage := resourceVersion == "" && !(consistentListFromCacheEnabled && requestWatchProgressSupported)
 	// Watch cache doesn't support continuations, so serve them from etcd.
 	hasContinuation := len(pred.Continue) > 0
-	// Serve paginated requests about revision "0" from watch cache to avoid overwhelming etcd.
-	hasLimit := pred.Limit > 0 && resourceVersion != "0"
 	// Watch cache only supports ResourceVersionMatchNotOlderThan (default).
-	unsupportedMatch := match != "" && match != metav1.ResourceVersionMatchNotOlderThan
+	// see https://kubernetes.io/docs/reference/using-api/api-concepts/#semantics-for-get-and-list
+	isLegacyExactMatch := opts.Predicate.Limit > 0 && match == "" && len(resourceVersion) > 0 && resourceVersion != "0"
+	unsupportedMatch := match != "" && match != metav1.ResourceVersionMatchNotOlderThan || isLegacyExactMatch
 
-	return consistentReadFromStorage || hasContinuation || hasLimit || unsupportedMatch
+	return consistentReadFromStorage || hasContinuation || unsupportedMatch
+}
+
+// computeListLimit determines whether the cacher should
+// apply a limit to an incoming LIST request and returns its value.
+//
+// note that this function doesn't check RVM nor the Continuation token.
+// these parameters are validated by the shouldDelegateList function.
+//
+// as of today, the limit is ignored for requests that set RV == 0
+func computeListLimit(opts storage.ListOptions) int64 {
+	if opts.Predicate.Limit <= 0 || opts.ResourceVersion == "0" {
+		return 0
+	}
+	return opts.Predicate.Limit
 }
 
 func shouldDelegateListOnNotReadyCache(opts storage.ListOptions) bool {
@@ -795,7 +809,7 @@ func (c *Cacher) listItems(ctx context.Context, listRV uint64, key string, pred
 		}
 		return nil, readResourceVersion, "", nil
 	}
-	return c.watchCache.WaitUntilFreshAndList(ctx, listRV, pred.MatcherIndex(ctx))
+	return c.watchCache.WaitUntilFreshAndList(ctx, listRV, key, pred.MatcherIndex(ctx))
 }
 
 // GetList implements storage.Interface
@@ -871,7 +885,6 @@ func (c *Cacher) GetList(ctx context.Context, key string, opts storage.ListOptio
 	if listVal.Kind() != reflect.Slice {
 		return fmt.Errorf("need a pointer to slice, got %v", listVal.Kind())
 	}
-	filter := filterWithAttrsFunction(preparedKey, pred)
 
 	objs, readResourceVersion, indexUsed, err := c.listItems(ctx, listRV, preparedKey, pred, recursive)
 	if err != nil {
@@ -883,13 +896,21 @@ func (c *Cacher) GetList(ctx context.Context, key string, opts storage.ListOptio
 	//   the elements in ListObject are Struct type, making slice will bring excessive memory consumption.
 	//   so we try to delay this action as much as possible
 	var selectedObjects []runtime.Object
-	for _, obj := range objs {
+	var lastSelectedObjectKey string
+	var hasMoreListItems bool
+	limit := computeListLimit(opts)
+	for i, obj := range objs {
 		elem, ok := obj.(*storeElement)
 		if !ok {
 			return fmt.Errorf("non *storeElement returned from storage: %v", obj)
 		}
-		if filter(elem.Key, elem.Labels, elem.Fields) {
+		if pred.MatchesObjectAttributes(elem.Labels, elem.Fields) {
 			selectedObjects = append(selectedObjects, elem.Object)
+			lastSelectedObjectKey = elem.Key
+		}
+		if limit > 0 && int64(len(selectedObjects)) >= limit {
+			hasMoreListItems = i < len(objs)-1
+			break
 		}
 	}
 	if len(selectedObjects) == 0 {
@@ -905,7 +926,12 @@ func (c *Cacher) GetList(ctx context.Context, key string, opts storage.ListOptio
 	}
 	span.AddEvent("Filtered items", attribute.Int("count", listVal.Len()))
 	if c.versioner != nil {
-		if err := c.versioner.UpdateList(listObj, readResourceVersion, "", nil); err != nil {
+		continueValue, remainingItemCount, err := storage.PrepareContinueToken(lastSelectedObjectKey, key, int64(readResourceVersion), int64(len(objs)), hasMoreListItems, opts)
+		if err != nil {
+			return err
+		}
+
+		if err = c.versioner.UpdateList(listObj, readResourceVersion, continueValue, remainingItemCount); err != nil {
 			return err
 		}
 	}
@@ -1293,7 +1319,7 @@ func forgetWatcher(c *Cacher, w *cacheWatcher, index int, scope namespacedName,
 	}
 }
 
-func filterWithAttrsFunction(key string, p storage.SelectionPredicate) filterWithAttrsFunc {
+func filterWithAttrsAndPrefixFunction(key string, p storage.SelectionPredicate) filterWithAttrsFunc {
 	filterFunc := func(objKey string, label labels.Set, field fields.Set) bool {
 		if !hasPathPrefix(objKey, key) {
 			return false

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

@@ -201,7 +201,6 @@ func TestGetListCacheBypass(t *testing.T) {
 		{opts: storage.ListOptions{ResourceVersion: "0", Predicate: storage.SelectionPredicate{Continue: "a"}}, expectBypass: true},
 		{opts: storage.ListOptions{ResourceVersion: "1", Predicate: storage.SelectionPredicate{Continue: "a"}}, expectBypass: true},
 
-		{opts: storage.ListOptions{ResourceVersion: "", Predicate: storage.SelectionPredicate{Limit: 500}}, expectBypass: true},
 		{opts: storage.ListOptions{ResourceVersion: "0", Predicate: storage.SelectionPredicate{Limit: 500}}, expectBypass: false},
 		{opts: storage.ListOptions{ResourceVersion: "1", Predicate: storage.SelectionPredicate{Limit: 500}}, expectBypass: true},
 
@@ -214,6 +213,7 @@ func TestGetListCacheBypass(t *testing.T) {
 		featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.ConsistentListFromCache, false)
 		testCases := append(commonTestCases,
 			testCase{opts: storage.ListOptions{ResourceVersion: ""}, expectBypass: true},
+			testCase{opts: storage.ListOptions{ResourceVersion: "", Predicate: storage.SelectionPredicate{Limit: 500}}, expectBypass: true},
 		)
 		for _, tc := range testCases {
 			testGetListCacheBypass(t, tc.opts, tc.expectBypass)
@@ -233,6 +233,7 @@ func TestGetListCacheBypass(t *testing.T) {
 
 		testCases := append(commonTestCases,
 			testCase{opts: storage.ListOptions{ResourceVersion: ""}, expectBypass: false},
+			testCase{opts: storage.ListOptions{ResourceVersion: "", Predicate: storage.SelectionPredicate{Limit: 500}}, expectBypass: false},
 		)
 		for _, tc := range testCases {
 			testGetListCacheBypass(t, tc.opts, tc.expectBypass)
@@ -2591,6 +2592,63 @@ func TestWatchStreamSeparation(t *testing.T) {
 	}
 }
 
+func TestComputeListLimit(t *testing.T) {
+	scenarios := []struct {
+		name          string
+		opts          storage.ListOptions
+		expectedLimit int64
+	}{
+		{
+			name: "limit is zero",
+			opts: storage.ListOptions{
+				Predicate: storage.SelectionPredicate{
+					Limit: 0,
+				},
+			},
+			expectedLimit: 0,
+		},
+		{
+			name: "limit is positive, RV is unset",
+			opts: storage.ListOptions{
+				Predicate: storage.SelectionPredicate{
+					Limit: 1,
+				},
+				ResourceVersion: "",
+			},
+			expectedLimit: 1,
+		},
+		{
+			name: "limit is positive, RV = 100",
+			opts: storage.ListOptions{
+				Predicate: storage.SelectionPredicate{
+					Limit: 1,
+				},
+				ResourceVersion: "100",
+			},
+			expectedLimit: 1,
+		},
+		{
+			name: "legacy case: limit is positive, RV = 0",
+			opts: storage.ListOptions{
+				Predicate: storage.SelectionPredicate{
+					Limit: 1,
+				},
+				ResourceVersion: "0",
+			},
+			expectedLimit: 0,
+		},
+	}
+
+	for _, scenario := range scenarios {
+		t.Run(scenario.name, func(t *testing.T) {
+			actualLimit := computeListLimit(scenario.opts)
+			if actualLimit != scenario.expectedLimit {
+				t.Errorf("computeListLimit returned = %v, expected %v", actualLimit, scenario.expectedLimit)
+			}
+		})
+	}
+}
+
 func watchAndWaitForBookmark(t *testing.T, ctx context.Context, etcdStorage storage.Interface) func() (resourceVersion uint64) {
 	opts := storage.ListOptions{ResourceVersion: "", Predicate: storage.Everything, Recursive: true}
 	opts.Predicate.AllowWatchBookmarks = true

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

@@ -501,7 +501,29 @@ func (s sortableStoreElements) Swap(i, j int) {
 
 // WaitUntilFreshAndList returns list of pointers to `storeElement` objects along
 // with their ResourceVersion and the name of the index, if any, that was used.
-func (w *watchCache) WaitUntilFreshAndList(ctx context.Context, resourceVersion uint64, matchValues []storage.MatchValue) (result []interface{}, rv uint64, index string, err error) {
+func (w *watchCache) WaitUntilFreshAndList(ctx context.Context, resourceVersion uint64, key string, matchValues []storage.MatchValue) ([]interface{}, uint64, string, error) {
+	items, rv, index, err := w.waitUntilFreshAndListItems(ctx, resourceVersion, key, matchValues)
+	if err != nil {
+		return nil, 0, "", err
+	}
+
+	var result []interface{}
+	for _, item := range items {
+		elem, ok := item.(*storeElement)
+		if !ok {
+			return nil, 0, "", fmt.Errorf("non *storeElement returned from storage: %v", item)
+		}
+		if !hasPathPrefix(elem.Key, key) {
+			continue
+		}
+		result = append(result, item)
+	}
+
+	sort.Sort(sortableStoreElements(result))
+	return result, rv, index, nil
+}
+
+func (w *watchCache) waitUntilFreshAndListItems(ctx context.Context, resourceVersion uint64, key string, matchValues []storage.MatchValue) (result []interface{}, rv uint64, index string, err error) {
 	requestWatchProgressSupported := etcdfeature.DefaultFeatureSupportChecker.Supports(storage.RequestWatchProgress)
 	if utilfeature.DefaultFeatureGate.Enabled(features.ConsistentListFromCache) && requestWatchProgressSupported && w.notFresh(resourceVersion) {
 		w.waitingUntilFresh.Add()
@@ -511,7 +533,6 @@ func (w *watchCache) WaitUntilFreshAndList(ctx context.Context, resourceVersion
 		err = w.waitUntilFreshAndBlock(ctx, resourceVersion)
 	}
 
-	defer func() { sort.Sort(sortableStoreElements(result)) }()
 	defer w.RUnlock()
 	if err != nil {
 		return result, rv, index, err

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

@@ -462,7 +462,7 @@ func TestWaitUntilFreshAndList(t *testing.T) {
 	}()
 
 	// list by empty MatchValues.
-	list, resourceVersion, indexUsed, err := store.WaitUntilFreshAndList(ctx, 5, nil)
+	list, resourceVersion, indexUsed, err := store.WaitUntilFreshAndList(ctx, 5, "prefix/", nil)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -481,7 +481,7 @@ func TestWaitUntilFreshAndList(t *testing.T) {
 		{IndexName: "l:label", Value: "value1"},
 		{IndexName: "f:spec.nodeName", Value: "node2"},
 	}
-	list, resourceVersion, indexUsed, err = store.WaitUntilFreshAndList(ctx, 5, matchValues)
+	list, resourceVersion, indexUsed, err = store.WaitUntilFreshAndList(ctx, 5, "prefix/", matchValues)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -500,7 +500,7 @@ func TestWaitUntilFreshAndList(t *testing.T) {
 		{IndexName: "l:not-exist-label", Value: "whatever"},
 		{IndexName: "f:spec.nodeName", Value: "node2"},
 	}
-	list, resourceVersion, indexUsed, err = store.WaitUntilFreshAndList(ctx, 5, matchValues)
+	list, resourceVersion, indexUsed, err = store.WaitUntilFreshAndList(ctx, 5, "prefix/", matchValues)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -518,7 +518,7 @@ func TestWaitUntilFreshAndList(t *testing.T) {
 	matchValues = []storage.MatchValue{
 		{IndexName: "l:not-exist-label", Value: "whatever"},
 	}
-	list, resourceVersion, indexUsed, err = store.WaitUntilFreshAndList(ctx, 5, matchValues)
+	list, resourceVersion, indexUsed, err = store.WaitUntilFreshAndList(ctx, 5, "prefix/", matchValues)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -546,7 +546,7 @@ func TestWaitUntilFreshAndListFromCache(t *testing.T) {
 	}()
 
 	// list from future revision. Requires watch cache to request bookmark to get it.
-	list, resourceVersion, indexUsed, err := store.WaitUntilFreshAndList(ctx, 3, nil)
+	list, resourceVersion, indexUsed, err := store.WaitUntilFreshAndList(ctx, 3, "prefix/", nil)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -626,7 +626,7 @@ func TestWaitUntilFreshAndListTimeout(t *testing.T) {
 				store.Add(makeTestPod("bar", 4))
 			}()
 
-			_, _, _, err := store.WaitUntilFreshAndList(ctx, 4, nil)
+			_, _, _, err := store.WaitUntilFreshAndList(ctx, 4, "", nil)
 			if !errors.IsTimeout(err) {
 				t.Errorf("expected timeout error but got: %v", err)
 			}
@@ -655,7 +655,7 @@ func TestReflectorForWatchCache(t *testing.T) {
 	defer store.Stop()
 
 	{
-		_, version, _, err := store.WaitUntilFreshAndList(ctx, 0, nil)
+		_, version, _, err := store.WaitUntilFreshAndList(ctx, 0, "", nil)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -678,7 +678,7 @@ func TestReflectorForWatchCache(t *testing.T) {
 	r.ListAndWatch(wait.NeverStop)
 
 	{
-		_, version, _, err := store.WaitUntilFreshAndList(ctx, 10, nil)
+		_, version, _, err := store.WaitUntilFreshAndList(ctx, 10, "", nil)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/request/list_work_estimator.go

@@ -173,10 +173,10 @@ func shouldListFromStorage(query url.Values, opts *metav1.ListOptions) bool {
 	consistentReadFromStorage := resourceVersion == "" && !(consistentListFromCacheEnabled && requestWatchProgressSupported)
 	// Watch cache doesn't support continuations, so serve them from etcd.
 	hasContinuation := len(opts.Continue) > 0
-	// Serve paginated requests about revision "0" from watch cache to avoid overwhelming etcd.
-	hasLimit := opts.Limit > 0 && resourceVersion != "0"
 	// Watch cache only supports ResourceVersionMatchNotOlderThan (default).
-	unsupportedMatch := match != "" && match != metav1.ResourceVersionMatchNotOlderThan
+	// see https://kubernetes.io/docs/reference/using-api/api-concepts/#semantics-for-get-and-list
+	isLegacyExactMatch := opts.Limit > 0 && match == "" && len(resourceVersion) > 0 && resourceVersion != "0"
+	unsupportedMatch := match != "" && match != metav1.ResourceVersionMatchNotOlderThan || isLegacyExactMatch
 
-	return consistentReadFromStorage || hasContinuation || hasLimit || unsupportedMatch
+	return consistentReadFromStorage || hasContinuation || unsupportedMatch
 }