Prevent invalid timestamps in page_fault_count metric

Right after container is started, kubelet returns time == start_time for
that metric, which causes Monitoring API to return 400 error.

Author: x13n

kubelet-to-gcm/Makefile

@@ -15,7 +15,7 @@
 OUT_DIR = build
 PACKAGE = github.com/GoogleCloudPlatform/k8s-stackdriver/kubelet-to-gcm
 PREFIX = staging-k8s.gcr.io
-TAG = 1.3.4
+TAG = 1.3.5
 
 # Rules for building the real image for deployment to gcr.io
 

kubelet-to-gcm/monitor/kubelet/translate.go

@@ -519,7 +519,8 @@ func translateMemory(memory *stats.MemoryStats, tsFactory *timeSeriesFactory, st
 		return nil, fmt.Errorf("Memory information missing.")
 	}
 
-	if pageFaultsMD != nil {
+	// Only send page fault metric if start time is before current time. Right after container is started, kubelet can return start time == end time. This doesn't seem to happen with other metrics.
+	if pageFaultsMD != nil && memory.Time.Time.After(startTime) {
 		if memory.MajorPageFaults == nil {
 			return nil, fmt.Errorf("MajorPageFaults missing in MemoryStats %v", memory)
 		}

kubelet-to-gcm/monitor/kubelet/translate_test.go

@@ -221,6 +221,8 @@ func TestTranslateContainers(t *testing.T) {
 	noLogStatsContainer.Logs = nil
 	noRootfsStatsContainer := *getContainerStats(false)
 	noRootfsStatsContainer.Rootfs = nil
+	badTimestampOnPageFaultContrainer := *getContainerStats(false)
+	badTimestampOnPageFaultContrainer.Memory.Time = badTimestampOnPageFaultContrainer.StartTime
 	legacyTsPerContainer := 11
 	tsPerContainer := 8
 	testCases := []struct {
@@ -307,6 +309,16 @@ func TestTranslateContainers(t *testing.T) {
 				),
 			},
 		},
+		{
+			name:                  "bad timestamp for page_fault_count",
+			ExpectedLegacyTSCount: legacyTsPerContainer - 2,
+			ExpectedTSCount:       tsPerContainer - 2,
+			pods: []stats.PodStats{
+				getPodStats(
+					badTimestampOnPageFaultContrainer,
+				),
+			},
+		},
 	}
 
 	for _, tc := range testCases {
@@ -349,6 +361,9 @@ func getContainerStats(skipUsageNanoCores bool) *stats.ContainerStats {
 	if skipUsageNanoCores {
 		v.CPU.UsageNanoCores = nil
 	}
+	if v.Memory.Time.Time.Before(v.StartTime.Time) {
+		v.Memory.Time, v.StartTime = v.StartTime, v.Memory.Time
+	}
 	return v
 }