throttler: Fix the aggregated average historic value if multiple threads are used. (#1985)

go/vt/throttler/aggregated_interval_history.go

@@ -35,5 +35,5 @@ func (h *aggregatedIntervalHistory) average(from, to time.Time) float64 {
 	for i := 0; i < h.threadCount; i++ {
 		sum += h.historyPerThread[i].average(from, to)
 	}
-	return sum / float64(h.threadCount)
+	return sum
 }

go/vt/throttler/aggregated_interval_history_test.go

@@ -0,0 +1,16 @@
+package throttler
+
+import (
+	"testing"
+	"time"
+)
+
+func TestAggregatedIntervalHistory(t *testing.T) {
+	h := newAggregatedIntervalHistory(10, 1*time.Second, 2)
+	h.addPerThread(0, record{sinceZero(0 * time.Second), 1000})
+	h.addPerThread(1, record{sinceZero(0 * time.Second), 2000})
+
+	if got, want := h.average(sinceZero(250*time.Millisecond), sinceZero(750*time.Millisecond)), 3000.0; got != want {
+		t.Errorf("average(0.25s, 0.75s) across both threads = %v, want = %v", got, want)
+	}
+}