Only return changed counts, and send initial count

Three main changes:
- When a count changes, only send that count. This makes the
count socket significantly more usable
- The count buffer will now send a count right away. This allows
a message to launch wihtout an inital buffered wait period
- The count buffer now sends messages every 5 seconds instead of 1

pkg/resources/counts/buffer.go

@@ -6,35 +6,60 @@ import (
 	"github.com/rancher/apiserver/pkg/types"
 )
 
-func buffer(c chan types.APIEvent) chan types.APIEvent {
+// debounceDuration determines how long events will be held before they are sent to the consumer
+var debounceDuration = 5 * time.Second
+
+// countsBuffer creates an APIEvent channel with a buffered response time (i.e. replies are only sent once every second)
+func countsBuffer(c chan Count) chan types.APIEvent {
 	result := make(chan types.APIEvent)
 	go func() {
 		defer close(result)
-		debounce(result, c)
+		debounceCounts(result, c)
 	}()
 	return result
 }
 
-func debounce(result, input chan types.APIEvent) {
-	t := time.NewTicker(time.Second)
+// debounceCounts converts counts from an input channel into an APIEvent, and updates the result channel at a reduced pace
+func debounceCounts(result chan types.APIEvent, input chan Count) {
+	// counts aren't a critical value. To avoid excess UI processing, only send updates after debounceDuration has elapsed
+	t := time.NewTicker(debounceDuration)
 	defer t.Stop()
 
-	var (
-		lastEvent *types.APIEvent
-	)
+	var currentCount *Count
+
+	firstCount, fOk := <-input
+	if fOk {
+		// send a count immediately or we will have to wait a second for the first update
+		result <- toAPIEvent(firstCount)
+	}
 	for {
 		select {
-		case event, ok := <-input:
-			if ok {
-				lastEvent = &event
-			} else {
+		case count, ok := <-input:
+			if !ok {
 				return
 			}
+			if currentCount == nil {
+				currentCount = &count
+			} else {
+				itemCounts := count.Counts
+				for id, itemCount := range itemCounts {
+					// our current count will be outdated in comparison with anything in the new events
+					currentCount.Counts[id] = itemCount
+				}
+			}
 		case <-t.C:
-			if lastEvent != nil {
-				result <- *lastEvent
-				lastEvent = nil
+			if currentCount != nil {
+				result <- toAPIEvent(*currentCount)
+				currentCount = nil
 			}
 		}
 	}
 }
+
+func toAPIEvent(count Count) types.APIEvent {
+	return types.APIEvent{
+		Name:         "resource.change",
+		ResourceType: "counts",
+		Object:       toAPIObject(count),
+	}
+}