Add etcd DB size monitoring in density test

test/e2e/scalability/density.go

@@ -395,6 +395,7 @@ var _ = SIGDescribe("Density", func() {
 	missingMeasurements := 0
 	var testPhaseDurations *timer.TestPhaseTimer
 	var profileGathererStopCh chan struct{}
+	var etcdMetricsCollector *framework.EtcdMetricsCollector
 
 	// Gathers data prior to framework namespace teardown
 	AfterEach(func() {
@@ -426,7 +427,7 @@ var _ = SIGDescribe("Density", func() {
 			summaries = append(summaries, metrics)
 		}
 
-		// Verify scheduler metrics.
+		// Summarize scheduler metrics.
 		latency, err := framework.VerifySchedulerLatency(c)
 		framework.ExpectNoError(err)
 		if err == nil {
@@ -443,10 +444,11 @@ var _ = SIGDescribe("Density", func() {
 			summaries = append(summaries, latency)
 		}
 
-		etcdMetrics, err := framework.VerifyEtcdMetrics(c)
+		// Summarize etcd metrics.
+		err = etcdMetricsCollector.StopAndSummarize()
 		framework.ExpectNoError(err)
 		if err == nil {
-			summaries = append(summaries, etcdMetrics)
+			summaries = append(summaries, etcdMetricsCollector.GetMetrics())
 		}
 
 		summaries = append(summaries, testPhaseDurations)
@@ -509,6 +511,10 @@ var _ = SIGDescribe("Density", func() {
 		// Start apiserver CPU profile gatherer with frequency based on cluster size.
 		profileGatheringDelay := time.Duration(5+nodeCount/100) * time.Minute
 		profileGathererStopCh = framework.StartCPUProfileGatherer("kube-apiserver", "density", profileGatheringDelay)
+
+		// Start etcs metrics collection.
+		etcdMetricsCollector = framework.NewEtcdMetricsCollector()
+		etcdMetricsCollector.StartCollecting(time.Minute)
 	})
 
 	type Density struct {