requestbatcher: deflake TestBatchTimeout

Fixes #97832.

This commit deflakes `TestBatchTimeout/WithTimeoutAndPagination`. The
test was setting an aggressive MaxTimeout and then not handling all
cases where the timeout could fire. Luckily, the test did not ever
actually want the timeout to fire, so we can deflake it by simply
setting a large (but non-zero) MaxTimeout. This still allows us to
assert that time timeout is applied across all sub-batches in a
paginated request.

Release note: None

pkg/internal/client/requestbatcher/batcher_test.go

@@ -320,7 +320,6 @@ func TestBatchTimeout(t *testing.T) {
 	const timeout = 5 * time.Millisecond
 	stopper := stop.NewStopper()
 	defer stopper.Stop(context.Background())
-	sc := make(chanSender)
 	testCases := []struct {
 		requestTimeout  time.Duration
 		maxTimeout      time.Duration
@@ -350,6 +349,7 @@ func TestBatchTimeout(t *testing.T) {
 	for _, tc := range testCases {
 		t.Run(fmt.Sprintf("With%sRequestTimeout%sMaxTimeout", tc.requestTimeout, tc.maxTimeout),
 			func(t *testing.T) {
+				sc := make(chanSender)
 				b := New(Config{
 					// MaxMsgsPerBatch of 1 is chosen so that the first call to Send will
 					// immediately lead to a batch being sent.
@@ -387,8 +387,9 @@ func TestBatchTimeout(t *testing.T) {
 		)
 	}
 	t.Run("WithTimeoutAndPagination", func(t *testing.T) {
-		maxTimeout := 20 * time.Millisecond
+		maxTimeout := 45 * time.Second
 		firstAndSecondSendTimeDiff := 10 * time.Millisecond
+		sc := make(chanSender)
 		b := New(Config{
 			// MaxMsgsPerBatch of 1 is chosen so that the first call to Send will
 			// immediately lead to a batch being sent.
@@ -398,13 +399,14 @@ func TestBatchTimeout(t *testing.T) {
 			MaxTimeout:      maxTimeout,
 		})
 		// This test will simulate multiple calls to Send (due to pagination) and
-		// test that the MaxTimeout set is a timeout per batch rather than a
-		// timeout per request.
+		// test that the MaxTimeout set is a timeout per batch rather than a timeout
+		// per request. MaxTimeout is set to a large value, so the timeout should
+		// never actually be hit. This means that the subtest does not face the same
+		// timing issues that the subtests above do.
+		ctx := context.Background()
 		respChan := make(chan Response, 1)
-		if err := b.SendWithChan(context.Background(), respChan, 1, &kvpb.GetRequest{}); err != nil {
-			testutils.IsError(err, context.DeadlineExceeded.Error())
-			return
-		}
+		err := b.SendWithChan(ctx, respChan, 1, &kvpb.GetRequest{})
+		require.NoError(t, err)
 		// First call to Send.
 		s := <-sc
 		time.Sleep(firstAndSecondSendTimeDiff)
@@ -432,6 +434,7 @@ func TestBatchTimeout(t *testing.T) {
 		s.respChan <- batchResp{}
 	})
 	t.Run("NoTimeout", func(t *testing.T) {
+		sc := make(chanSender)
 		b := New(Config{
 			// MaxMsgsPerBatch of 2 is chosen so that the second call to Send will
 			// immediately lead to a batch being sent.