Only enqueue non-terminal tasks (#164)

Signed-off-by: Kevin Su <pingsutw@apache.org>

cache/auto_refresh.go

@@ -56,7 +56,9 @@ type metrics struct {
 	scope       promutils.Scope
 }
 
-type Item interface{}
+type Item interface {
+	IsTerminal() bool
+}
 
 // Items are wrapped inside an ItemWrapper to be stored in the cache.
 type ItemWrapper interface {
@@ -164,7 +166,7 @@ func (w *autoRefresh) Start(ctx context.Context) error {
 	go wait.Until(func() {
 		err := w.enqueueBatches(enqueueCtx)
 		if err != nil {
-			logger.Errorf(enqueueCtx, "Failed to sync. Error: %v", err)
+			logger.Errorf(enqueueCtx, "Failed to enqueue. Error: %v", err)
 		}
 	}, w.syncPeriod, enqueueCtx.Done())
 
@@ -209,13 +211,20 @@ func (w *autoRefresh) enqueueBatches(ctx context.Context) error {
 
 	snapshot := make([]ItemWrapper, 0, len(keys))
 	for _, k := range keys {
+		if w.toDelete.Contains(k) {
+			w.lruMap.Remove(k)
+			w.toDelete.Remove(k)
+			continue
+		}
 		// If not ok, it means evicted between the item was evicted between getting the keys and this update loop
 		// which is fine, we can just ignore.
-		if value, ok := w.lruMap.Peek(k); ok && !w.toDelete.Contains(k) {
-			snapshot = append(snapshot, itemWrapper{
-				id:   k.(ItemID),
-				item: value.(Item),
-			})
+		if value, ok := w.lruMap.Peek(k); ok {
+			if item, ok := value.(Item); !ok || (ok && !item.IsTerminal()) {
+				snapshot = append(snapshot, itemWrapper{
+					id:   k.(ItemID),
+					item: value.(Item),
+				})
+			}
 		}
 	}
 

cache/auto_refresh_example_test.go

@@ -26,6 +26,10 @@ type ExampleCacheItem struct {
 	id     string
 }
 
+func (e *ExampleCacheItem) IsTerminal() bool {
+	return e.status == ExampleStatusSucceeded
+}
+
 func (e *ExampleCacheItem) ID() string {
 	return e.id
 }

cache/auto_refresh_test.go

@@ -25,6 +25,18 @@ type fakeCacheItem struct {
 	val int
 }
 
+func (f fakeCacheItem) IsTerminal() bool {
+	return false
+}
+
+type terminalCacheItem struct {
+	val int
+}
+
+func (t terminalCacheItem) IsTerminal() bool {
+	return true
+}
+
 func syncFakeItem(_ context.Context, batch Batch) ([]ItemSyncResponse, error) {
 	items := make([]ItemSyncResponse, 0, len(batch))
 	for _, obj := range batch {
@@ -46,7 +58,11 @@ func syncFakeItem(_ context.Context, batch Batch) ([]ItemSyncResponse, error) {
 	return items, nil
 }
 
-func TestCacheTwo(t *testing.T) {
+func syncTerminalItem(_ context.Context, batch Batch) ([]ItemSyncResponse, error) {
+	panic("This should never be called")
+}
+
+func TestCacheThree(t *testing.T) {
 	testResyncPeriod := time.Millisecond
 	rateLimiter := workqueue.DefaultControllerRateLimiter()
 
@@ -104,6 +120,28 @@ func TestCacheTwo(t *testing.T) {
 
 		cancel()
 	})
+
+	t.Run("Enqueue nothing", func(t *testing.T) {
+		cache, err := NewAutoRefreshCache("fake3", syncTerminalItem, rateLimiter, testResyncPeriod, 10, 2, promutils.NewTestScope())
+		assert.NoError(t, err)
+
+		ctx, cancel := context.WithCancel(context.Background())
+		assert.NoError(t, cache.Start(ctx))
+
+		// Create ten items in the cache
+		for i := 1; i <= 10; i++ {
+			_, err := cache.GetOrCreate(fmt.Sprintf("%d", i), terminalCacheItem{
+				val: 0,
+			})
+			assert.NoError(t, err)
+		}
+
+		// Wait half a second for all resync periods to complete
+		// If the cache tries to enqueue the item, a panic will be thrown.
+		time.Sleep(500 * time.Millisecond)
+
+		cancel()
+	})
 }
 
 func TestQueueBuildUp(t *testing.T) {
@@ -134,7 +172,7 @@ func TestQueueBuildUp(t *testing.T) {
 	defer cancelNow()
 
 	for i := 0; i < size; i++ {
-		_, err := cache.GetOrCreate(strconv.Itoa(i), "test")
+		_, err := cache.GetOrCreate(strconv.Itoa(i), fakeCacheItem{val: 3})
 		assert.NoError(t, err)
 	}