stream: remove bufferItem.NextLink

Both NextLink and NextNoBlock had the same logic, with slightly
different return values. By adding a bool return value (similar to map
lookups) we can remove the duplicate method.

agent/consul/stream/event_buffer.go

@@ -81,7 +81,7 @@ func (b *eventBuffer) Append(events []Event) {
 	b.AppendItem(newBufferItem(events))
 }
 
-// AppendBuffer joins another buffer which may be the tail of a separate buffer
+// AppendItem joins another buffer which may be the tail of a separate buffer
 // for example a buffer that's had the events from a snapshot appended may
 // finally by linked to the topic buffer for the subsequent events so
 // subscribers can seamlessly consume the updates. Note that Events in item must
@@ -194,27 +194,19 @@ func (i *bufferItem) Next(ctx context.Context, closed <-chan struct{}) (*bufferI
 	return next, nil
 }
 
-// NextNoBlock returns the next item in the buffer without blocking. If it
+// NextNoBlock returns true and the next item in the buffer without blocking.
-// reaches the most recent item it will return nil.
+// If there are no subsequent items it returns false and an empty item.
-func (i *bufferItem) NextNoBlock() *bufferItem {
+// The empty item will be ignored by subscribers, but has the same link as this
+// bufferItem without the Events.
+// When the link.ch of the empty item is closed, subscriptions are notified of
+// the next item.
+func (i *bufferItem) NextNoBlock() (*bufferItem, bool) {
 	nextRaw := i.link.next.Load()
 	if nextRaw == nil {
-		return nil
-	}
-	return nextRaw.(*bufferItem)
-}
-
-// NextLink returns either the next item in the buffer if there is one, or
-// an empty item (that will be ignored by subscribers) that has a pointer to
-// the same link as this bufferItem (but none of the bufferItem content).
-// When the link.ch is closed, subscriptions will be notified of the next item.
-func (i *bufferItem) NextLink() *bufferItem {
-	next := i.NextNoBlock()
-	if next == nil {
 		// Return an empty item that can be followed to the next item published.
-		return &bufferItem{link: i.link}
+		return &bufferItem{link: i.link}, false
 	}
-	return next
+	return nextRaw.(*bufferItem), true
 }
 
 // HasEventIndex returns true if index matches the Event.Index of this item. Returns

agent/consul/stream/event_buffer_test.go

@@ -17,10 +17,6 @@ func TestEventBufferFuzz(t *testing.T) {
 		t.Skip("too slow for testing.Short")
 	}
 
-	if testing.Short() {
-		t.Skip("too slow for short run")
-	}
-
 	nReaders := 1000
 	nMessages := 1000
 

agent/consul/stream/event_publisher.go

@@ -171,7 +171,8 @@ func (e *EventPublisher) Subscribe(req *SubscribeRequest) (*Subscription, error)
 		subscriptionHead := buf.Head()
 		// splice the rest of the topic buffer onto the subscription buffer so
 		// the subscription will receive new events.
-		buf.AppendItem(topicHead.NextLink())
+		next, _ := topicHead.NextNoBlock()
+		buf.AppendItem(next)
 		return e.subscriptions.add(req, subscriptionHead), nil
 	}
 

agent/consul/stream/event_snapshot.go

@@ -67,12 +67,12 @@ func (s *eventSnapshot) spliceFromTopicBuffer(topicBufferHead *bufferItem, idx u
 			return
 		}
 
-		next := item.NextNoBlock()
+		next, ok := item.NextNoBlock()
-		if next == nil {
+		if !ok {
 			// We reached the head of the topic buffer. We don't want any of the
 			// events in the topic buffer as they came before the snapshot.
 			// Append a link to any future items.
-			s.buffer.AppendItem(item.NextLink())
+			s.buffer.AppendItem(next)
 			return
 		}
 		// Proceed to the next item in the topic buffer

agent/consul/stream/event_snapshot_test.go

@@ -95,7 +95,7 @@ func TestEventSnapshot(t *testing.T) {
 			// be appended before the snapshot fn executes in another goroutine since
 			// it's operating an a possible stale "snapshot". This is the same as
 			// reality with the state store where updates that occur after the
-			// snapshot is taken but while the SnapFnis still running must be captured
+			// snapshot is taken but while the SnapFn is still running must be captured
 			// correctly.
 			for i := 0; i < tc.updatesAfterSnap; i++ {
 				index := snapIndex + 1 + uint64(i)