Disable image GC when high threshold is set to 100

cmd/kubelet/app/options/options.go

@@ -486,7 +486,7 @@ func AddKubeletConfigFlags(fs *pflag.FlagSet, c *kubeletconfig.KubeletConfigurat
 	fs.DurationVar(&c.StreamingConnectionIdleTimeout.Duration, "streaming-connection-idle-timeout", c.StreamingConnectionIdleTimeout.Duration, "Maximum time a streaming connection can be idle before the connection is automatically closed. 0 indicates no timeout. Example: '5m'")
 	fs.DurationVar(&c.NodeStatusUpdateFrequency.Duration, "node-status-update-frequency", c.NodeStatusUpdateFrequency.Duration, "Specifies how often kubelet posts node status to master. Note: be cautious when changing the constant, it must work with nodeMonitorGracePeriod in nodecontroller.")
 	fs.DurationVar(&c.ImageMinimumGCAge.Duration, "minimum-image-ttl-duration", c.ImageMinimumGCAge.Duration, "Minimum age for an unused image before it is garbage collected.  Examples: '300ms', '10s' or '2h45m'.")
-	fs.Int32Var(&c.ImageGCHighThresholdPercent, "image-gc-high-threshold", c.ImageGCHighThresholdPercent, "The percent of disk usage after which image garbage collection is always run.Values must be winthin the range [0, 100], To disable image garbage collection, set to 0. ")
+	fs.Int32Var(&c.ImageGCHighThresholdPercent, "image-gc-high-threshold", c.ImageGCHighThresholdPercent, "The percent of disk usage after which image garbage collection is always run. Values must be winthin the range [0, 100], To disable image garbage collection, set to 100. ")
 	fs.Int32Var(&c.ImageGCLowThresholdPercent, "image-gc-low-threshold", c.ImageGCLowThresholdPercent, "The percent of disk usage before which image garbage collection is never run. Lowest disk usage to garbage collect to. Values must be winthin the range [0, 100] and should not be larger than that of --image-gc-high-threshold.")
 	fs.DurationVar(&c.VolumeStatsAggPeriod.Duration, "volume-stats-agg-period", c.VolumeStatsAggPeriod.Duration, "Specifies interval for kubelet to calculate and cache the volume disk usage for all pods and volumes.  To disable volume calculations, set to 0.")
 	fs.Var(flag.NewMapStringBool(&c.FeatureGates), "feature-gates", "A set of key=value pairs that describe feature gates for alpha/experimental features. "+

pkg/kubelet/images/image_gc_manager.go

@@ -290,11 +290,6 @@ func (im *realImageGCManager) GarbageCollect() error {
 
 	// If over the max threshold, free enough to place us at the lower threshold.
 	usagePercent := 100 - int(available*100/capacity)
-	if im.policy.HighThresholdPercent == 0 {
-		glog.Warningf("Disk usage percent is %d, the high threshold is 0, will not image GC on device %q at mount point %q", usagePercent, fsInfo.Device, fsInfo.Mountpoint)
-		return nil
-	}
-
 	if usagePercent >= im.policy.HighThresholdPercent {
 		amountToFree := capacity*int64(100-im.policy.LowThresholdPercent)/100 - available
 		glog.Infof("[imageGCManager]: Disk usage on image filesystem is at %d%% which is over the high threshold (%d%%). Trying to free %d bytes", usagePercent, im.policy.HighThresholdPercent, amountToFree)

pkg/kubelet/kubelet.go

@@ -1245,6 +1245,14 @@ func (kl *Kubelet) StartGarbageCollection() {
 		}
 	}, ContainerGCPeriod, wait.NeverStop)
 
+	stopChan := make(chan struct{})
+	defer close(stopChan)
+	// when the high threshold is set to 100, stub the image GC manager
+	if kl.kubeletConfiguration.ImageGCHighThresholdPercent == 100 {
+		glog.V(2).Infof("ImageGCHighThresholdPercent is set 100, Disable image GC")
+		go func() { stopChan <- struct{}{} }()
+	}
+
 	prevImageGCFailed := false
 	go wait.Until(func() {
 		if err := kl.imageManager.GarbageCollect(); err != nil {
@@ -1265,7 +1273,7 @@ func (kl *Kubelet) StartGarbageCollection() {
 
 			glog.V(vLevel).Infof("Image garbage collection succeeded")
 		}
-	}, ImageGCPeriod, wait.NeverStop)
+	}, ImageGCPeriod, stopChan)
 }
 
 // initializeModules will initialize internal modules that do not require the container runtime to be up.