prevents garbage collection from removing pinned images

pkg/kubelet/container/runtime.go

@@ -371,6 +371,8 @@ type Image struct {
 	Size int64
 	// ImageSpec for the image which include annotations.
 	Spec ImageSpec
+	// Pin for preventing garbage collection
+	Pinned bool
 }
 
 // EnvVar represents the environment variable.

pkg/kubelet/images/image_gc_manager.go

@@ -146,6 +146,9 @@ type imageRecord struct {
 
 	// Size of the image in bytes.
 	size int64
+
+	// Pinned status of the image
+	pinned bool
 }
 
 // NewImageGCManager instantiates a new ImageGCManager object.
@@ -257,6 +260,9 @@ func (im *realImageGCManager) detectImages(detectTime time.Time) (sets.String, e
 
 		klog.V(5).InfoS("Image ID has size", "imageID", image.ID, "size", image.Size)
 		im.imageRecords[image.ID].size = image.Size
+
+		klog.V(5).InfoS("Image ID is pinned", "imageID", image.ID, "pinned", image.Pinned)
+		im.imageRecords[image.ID].pinned = image.Pinned
 	}
 
 	// Remove old images from our records.
@@ -345,6 +351,12 @@ func (im *realImageGCManager) freeSpace(bytesToFree int64, freeTime time.Time) (
 			klog.V(5).InfoS("Image ID is being used", "imageID", image)
 			continue
 		}
+		// Check if image is pinned, prevent garbage collection
+		if record.pinned {
+			klog.V(5).InfoS("Image is pinned, skipping garbage collection", "imageID", image)
+			continue
+
+		}
 		images = append(images, evictionInfo{
 			id:          image,
 			imageRecord: *record,

pkg/kubelet/images/image_gc_manager_test.go

@@ -206,6 +206,102 @@ func TestDeleteUnusedImagesExemptSandboxImage(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestDeletePinnedImage(t *testing.T) {
+	mockCtrl := gomock.NewController(t)
+	mockStatsProvider := statstest.NewMockProvider(mockCtrl)
+
+	manager, fakeRuntime := newRealImageGCManager(ImageGCPolicy{}, mockStatsProvider)
+	fakeRuntime.ImageList = []container.Image{
+		{
+			ID:     sandboxImage,
+			Size:   1024,
+			Pinned: true,
+		},
+		{
+			ID:   sandboxImage,
+			Size: 1024,
+		},
+	}
+
+	err := manager.DeleteUnusedImages()
+	assert := assert.New(t)
+	assert.Len(fakeRuntime.ImageList, 2)
+	require.NoError(t, err)
+}
+
+func TestDoNotDeletePinnedImage(t *testing.T) {
+	mockCtrl := gomock.NewController(t)
+	mockStatsProvider := statstest.NewMockProvider(mockCtrl)
+
+	manager, fakeRuntime := newRealImageGCManager(ImageGCPolicy{}, mockStatsProvider)
+	fakeRuntime.ImageList = []container.Image{
+		{
+			ID:     "1",
+			Size:   1024,
+			Pinned: true,
+		},
+		{
+			ID:   "2",
+			Size: 1024,
+		},
+	}
+
+	spaceFreed, err := manager.freeSpace(4096, time.Now())
+	assert := assert.New(t)
+	require.NoError(t, err)
+	assert.EqualValues(1024, spaceFreed)
+	assert.Len(fakeRuntime.ImageList, 1)
+}
+
+func TestDeleteUnPinnedImage(t *testing.T) {
+	mockCtrl := gomock.NewController(t)
+	mockStatsProvider := statstest.NewMockProvider(mockCtrl)
+
+	manager, fakeRuntime := newRealImageGCManager(ImageGCPolicy{}, mockStatsProvider)
+	fakeRuntime.ImageList = []container.Image{
+		{
+			ID:     "1",
+			Size:   1024,
+			Pinned: false,
+		},
+		{
+			ID:   "2",
+			Size: 1024,
+		},
+	}
+
+	spaceFreed, err := manager.freeSpace(2048, time.Now())
+	assert := assert.New(t)
+	require.NoError(t, err)
+	assert.EqualValues(2048, spaceFreed)
+	assert.Len(fakeRuntime.ImageList, 0)
+}
+
+func TestAllPinnedImages(t *testing.T) {
+	mockCtrl := gomock.NewController(t)
+	mockStatsProvider := statstest.NewMockProvider(mockCtrl)
+
+	manager, fakeRuntime := newRealImageGCManager(ImageGCPolicy{}, mockStatsProvider)
+	fakeRuntime.ImageList = []container.Image{
+		{
+			ID:     "1",
+			Size:   1024,
+			Pinned: true,
+		},
+		{
+			ID:     "2",
+			Size:   1024,
+			Pinned: true,
+		},
+	}
+
+	spaceFreed, err := manager.freeSpace(2048, time.Now())
+	assert := assert.New(t)
+	require.NoError(t, err)
+	assert.EqualValues(0, spaceFreed)
+	assert.Len(fakeRuntime.ImageList, 2)
+}
+
 func TestDetectImagesContainerStopped(t *testing.T) {
 	mockCtrl := gomock.NewController(t)
 	defer mockCtrl.Finish()