fix: Fix duplicate enqueue item problem in bloom download queue when do sync download (#13114)

A missing return will cause item enqueued twice in sync download scenario. That cause the response not like expected.

Suppose we want to fetch a blocks array: [0, 1, 2]. Enqueued items are [0, 0, 1, 1, 2, 2]，If we want response sorted we wait 3 times response will get [0, 0, 1]

pkg/storage/stores/shipper/bloomshipper/fetcher.go

@@ -502,6 +502,7 @@ func newDownloadQueue[T any, R any](size, workers int, process processFunc[T, R]
 func (q *downloadQueue[T, R]) enqueue(t downloadRequest[T, R]) {
 	if !t.async {
 		q.queue <- t
+		return
 	}
 	// for async task we attempt to dedupe task already in progress.
 	q.enqueuedMutex.Lock()

pkg/storage/stores/shipper/bloomshipper/fetcher_test.go

@@ -267,6 +267,59 @@ func TestFetcher_DownloadQueue(t *testing.T) {
 		}
 
 	})
+
+	t.Run("download multiple items and return in order", func(t *testing.T) {
+		ctx := context.Background()
+
+		q, err := newDownloadQueue[bool, bool](
+			100,
+			1,
+			func(_ context.Context, r downloadRequest[bool, bool]) {
+				r.results <- downloadResponse[bool]{
+					key:  r.key,
+					idx:  r.idx,
+					item: true,
+				}
+			},
+			log.NewNopLogger(),
+		)
+		require.NoError(t, err)
+
+		count := 10
+		resultsCh := make(chan downloadResponse[bool], count)
+		errorsCh := make(chan error, count)
+
+		reqs := buildDownloadRequest(ctx, count, resultsCh, errorsCh)
+		for _, r := range reqs {
+			q.enqueue(r)
+		}
+
+		for i := 0; i < count; i++ {
+			select {
+			case err := <-errorsCh:
+				require.False(t, true, "got %+v should have received a response instead", err)
+			case res := <-resultsCh:
+				require.True(t, res.item)
+				require.Equal(t, reqs[i].key, res.key)
+				require.Equal(t, reqs[i].idx, res.idx)
+			}
+		}
+	})
+}
+
+func buildDownloadRequest(ctx context.Context, count int, resCh chan downloadResponse[bool], errCh chan error) []downloadRequest[bool, bool] {
+	requests := make([]downloadRequest[bool, bool], count)
+	for i := 0; i < count; i++ {
+		requests[i] = downloadRequest[bool, bool]{
+			ctx:     ctx,
+			item:    false,
+			key:     "test",
+			idx:     i,
+			results: resCh,
+			errors:  errCh,
+		}
+	}
+	return requests
 }
 
 func TestFetcher_LoadBlocksFromFS(t *testing.T) {