Add StallWait option for async js.publish

Signed-off-by: Waldemar Quevedo <wally@nats.io>

js.go

@@ -345,6 +345,8 @@ type pubOpts struct {
 	rwait time.Duration // Retry wait between attempts
 	rnum  int           // Retry attempts
 
+	// stallWait is the max wait of a async pub ack.
+	stallWait time.Duration
 }
 
 // pubAckResponse is the ack response from the JetStream API when publishing a message.
@@ -400,6 +402,9 @@ func (js *js) PublishMsg(m *Msg, opts ...PubOpt) (*PubAck, error) {
 	if o.ttl == 0 && o.ctx == nil {
 		o.ttl = js.opts.wait
 	}
+	if o.stallWait > 0 {
+		return nil, fmt.Errorf("nats: stall wait cannot be set to sync publish")
+	}
 
 	if o.id != _EMPTY_ {
 		m.Header.Set(MsgIdHdr, o.id)
@@ -710,6 +715,8 @@ func (js *js) PublishAsync(subj string, data []byte, opts ...PubOpt) (PubAckFutu
 	return js.PublishMsgAsync(&Msg{Subject: subj, Data: data}, opts...)
 }
 
+const defaultStallWait = 200 * time.Millisecond
+
 func (js *js) PublishMsgAsync(m *Msg, opts ...PubOpt) (PubAckFuture, error) {
 	var o pubOpts
 	if len(opts) > 0 {
@@ -727,6 +734,10 @@ func (js *js) PublishMsgAsync(m *Msg, opts ...PubOpt) (PubAckFuture, error) {
 	if o.ttl != 0 || o.ctx != nil {
 		return nil, ErrContextAndTimeout
 	}
+	stallWait := defaultStallWait
+	if o.stallWait > 0 {
+		stallWait = o.stallWait
+	}
 
 	// FIXME(dlc) - Make common.
 	if o.id != _EMPTY_ {
@@ -764,7 +775,7 @@ func (js *js) PublishMsgAsync(m *Msg, opts ...PubOpt) (PubAckFuture, error) {
 	if maxPending > 0 && numPending >= maxPending {
 		select {
 		case <-js.asyncStall():
-		case <-time.After(200 * time.Millisecond):
+		case <-time.After(stallWait):
 			js.clearPAF(id)
 			return nil, errors.New("nats: stalled with too many outstanding async published messages")
 		}
@@ -848,6 +859,17 @@ func RetryAttempts(num int) PubOpt {
 	})
 }
 
+// StallWait sets the max wait when the producer becomes stall producing messages.
+func StallWait(ttl time.Duration) PubOpt {
+	return pubOptFn(func(opts *pubOpts) error {
+		if ttl <= 0 {
+			return fmt.Errorf("nats: stall wait should be more than 0")
+		}
+		opts.stallWait = ttl
+		return nil
+	})
+}
+
 type ackOpts struct {
 	ttl      time.Duration
 	ctx      context.Context

test/js_test.go

@@ -5337,6 +5337,19 @@ func TestJetStreamPublishAsync(t *testing.T) {
 	case <-time.After(5 * time.Second):
 		t.Fatalf("Did not receive completion signal")
 	}
+
+	// Check invalid options
+	_, err = js.PublishAsync("foo", []byte("Bad"), nats.StallWait(0))
+	expectedErr := "nats: stall wait should be more than 0"
+	if err == nil || err.Error() != expectedErr {
+		t.Errorf("Expected %v, got: %v", expectedErr, err)
+	}
+
+	_, err = js.Publish("foo", []byte("Also bad"), nats.StallWait(200*time.Millisecond))
+	expectedErr = "nats: stall wait cannot be set to sync publish"
+	if err == nil || err.Error() != expectedErr {
+		t.Errorf("Expected %v, got: %v", expectedErr, err)
+	}
 }
 
 func TestJetStreamPublishAsyncPerf(t *testing.T) {