Allow tokenCh of batch controller be nil

Signed-off-by: JmPotato <[email protected]>

client/pkg/batch/batch_controller.go

@@ -66,7 +66,7 @@ func (bc *Controller[T]) FetchPendingRequests(ctx context.Context, requestCh <-c
 		if errRet != nil {
 			// Something went wrong when collecting a batch of requests. Release the token and cancel collected requests
 			// if any.
-			if tokenAcquired {
+			if tokenAcquired && tokenCh != nil {
 				tokenCh <- struct{}{}
 			}
 			bc.FinishCollectedRequests(bc.finisher, errRet)
@@ -80,6 +80,9 @@ func (bc *Controller[T]) FetchPendingRequests(ctx context.Context, requestCh <-c
 		// If the batch size reaches the maxBatchSize limit but the token haven't arrived yet, don't receive more
 		// requests, and return when token is ready.
 		if bc.collectedRequestCount >= bc.maxBatchSize && !tokenAcquired {
+			if tokenCh == nil {
+				return nil
+			}
 			select {
 			case <-ctx.Done():
 				return ctx.Err()
@@ -88,17 +91,19 @@ func (bc *Controller[T]) FetchPendingRequests(ctx context.Context, requestCh <-c
 			}
 		}
 
-		select {
-		case <-ctx.Done():
-			return ctx.Err()
-		case req := <-requestCh:
-			// Start to batch when the first request arrives.
-			bc.pushRequest(req)
-			// A request arrives but the token is not ready yet. Continue waiting, and also allowing collecting the next
-			// request if it arrives.
-			continue
-		case <-tokenCh:
-			tokenAcquired = true
+		if tokenCh != nil {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case req := <-requestCh:
+				// Start to batch when the first request arrives.
+				bc.pushRequest(req)
+				// A request arrives but the token is not ready yet. Continue waiting, and also allowing collecting the next
+				// request if it arrives.
+				continue
+			case <-tokenCh:
+				tokenAcquired = true
+			}
 		}
 
 		// The token is ready. If the first request didn't arrive, wait for it.

client/pkg/batch/batch_controller_test.go

@@ -21,9 +21,11 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+const testMaxBatchSize = 20
+
 func TestAdjustBestBatchSize(t *testing.T) {
 	re := require.New(t)
-	bc := NewController[int](20, nil, nil)
+	bc := NewController[int](testMaxBatchSize, nil, nil)
 	re.Equal(defaultBestBatchSize, bc.bestBatchSize)
 	bc.AdjustBestBatchSize()
 	re.Equal(defaultBestBatchSize-1, bc.bestBatchSize)
@@ -52,7 +54,7 @@ type testRequest struct {
 
 func TestFinishCollectedRequests(t *testing.T) {
 	re := require.New(t)
-	bc := NewController[*testRequest](20, nil, nil)
+	bc := NewController[*testRequest](testMaxBatchSize, nil, nil)
 	// Finish with zero request count.
 	re.Zero(bc.collectedRequestCount)
 	bc.FinishCollectedRequests(nil, nil)
@@ -81,3 +83,58 @@ func TestFinishCollectedRequests(t *testing.T) {
 		re.Equal(context.Canceled, requests[i].err)
 	}
 }
+
+func TestFetchPendingRequests(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	re := require.New(t)
+	bc := NewController[int](testMaxBatchSize, nil, nil)
+	requestCh := make(chan int, testMaxBatchSize+1)
+	// Fetch a nil `tokenCh`.
+	requestCh <- 1
+	re.NoError(bc.FetchPendingRequests(ctx, requestCh, nil, 0))
+	re.Empty(requestCh)
+	re.Equal(1, bc.collectedRequestCount)
+	// Fetch a nil `tokenCh` with max batch size.
+	for i := range testMaxBatchSize {
+		requestCh <- i
+	}
+	re.NoError(bc.FetchPendingRequests(ctx, requestCh, nil, 0))
+	re.Empty(requestCh)
+	re.Equal(testMaxBatchSize, bc.collectedRequestCount)
+	// Fetch a nil `tokenCh` with max batch size + 1.
+	for i := range testMaxBatchSize + 1 {
+		requestCh <- i
+	}
+	re.NoError(bc.FetchPendingRequests(ctx, requestCh, nil, 0))
+	re.Len(requestCh, 1)
+	re.Equal(testMaxBatchSize, bc.collectedRequestCount)
+	// Drain the requestCh.
+	<-requestCh
+	// Fetch a non-nil `tokenCh`.
+	tokenCh := make(chan struct{}, 1)
+	requestCh <- 1
+	tokenCh <- struct{}{}
+	re.NoError(bc.FetchPendingRequests(ctx, requestCh, tokenCh, 0))
+	re.Empty(requestCh)
+	re.Equal(1, bc.collectedRequestCount)
+	// Fetch a non-nil `tokenCh` with max batch size.
+	for i := range testMaxBatchSize {
+		requestCh <- i
+	}
+	tokenCh <- struct{}{}
+	re.NoError(bc.FetchPendingRequests(ctx, requestCh, tokenCh, 0))
+	re.Empty(requestCh)
+	re.Equal(testMaxBatchSize, bc.collectedRequestCount)
+	// Fetch a non-nil `tokenCh` with max batch size + 1.
+	for i := range testMaxBatchSize + 1 {
+		requestCh <- i
+	}
+	tokenCh <- struct{}{}
+	re.NoError(bc.FetchPendingRequests(ctx, requestCh, tokenCh, 0))
+	re.Len(requestCh, 1)
+	re.Equal(testMaxBatchSize, bc.collectedRequestCount)
+	// Drain the requestCh.
+	<-requestCh
+}