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

@@ -338,6 +338,16 @@ func (im *realImageGCManager) freeSpace(bytesToFree int64, freeTime time.Time) (
 	im.imageRecordsLock.Lock()
 	defer im.imageRecordsLock.Unlock()
 
+	// Make the ListImages into a map to grab an image by ID
+	allImages, err := im.runtime.ListImages()
+	if err != nil {
+		return 0, err
+	}
+	imagesMap := make(map[string]container.Image, len(allImages))
+	for _, img := range allImages {
+		imagesMap[img.ID] = img
+	}
+
 	// Get all images in eviction order.
 	images := make([]evictionInfo, 0, len(im.imageRecords))
 	for image, record := range im.imageRecords {
@@ -345,6 +355,12 @@ 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 imagesMap[image].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 +206,89 @@ func TestDeleteUnusedImagesExemptSandboxImage(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestDeletePinnedImage(t *testing.T) {
+	manager, fakeRuntime, _ := newRealImageGCManager(ImageGCPolicy{})
+	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) {
+	manager, fakeRuntime, _ := newRealImageGCManager(ImageGCPolicy{})
+	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) {
+	manager, fakeRuntime, _ := newRealImageGCManager(ImageGCPolicy{})
+	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) {
+	manager, fakeRuntime, _ := newRealImageGCManager(ImageGCPolicy{})
+	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()

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.pb.go

@@ -6048,7 +6048,7 @@ type Image struct {
 	// ImageSpec for image which includes annotations
 	Spec *ImageSpec `protobuf:"bytes,7,opt,name=spec,proto3" json:"spec,omitempty"`
 	// Recommendation on whether this image should be exempt from garbage collection.
-	// It must only be treated as a recommendation--the client can still request the image be deleted,
+	// It must only be treated as a recommendation -- the client can still request that the image be deleted,
 	// and the runtime must oblige.
 	Pinned               bool     `protobuf:"varint,8,opt,name=pinned,proto3" json:"pinned,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto

@@ -1248,7 +1248,7 @@ message Image {
     // ImageSpec for image which includes annotations
     ImageSpec spec = 7;
     // Recommendation on whether this image should be exempt from garbage collection.
-    // It must only be treated as a recommendation--the client can still request the image be deleted,
+    // It must only be treated as a recommendation -- the client can still request that the image be deleted,
     // and the runtime must oblige.
     bool pinned = 8;
 }

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1alpha2/api.pb.go

@@ -6057,7 +6057,7 @@ type Image struct {
 	// ImageSpec for image which includes annotations
 	Spec *ImageSpec `protobuf:"bytes,7,opt,name=spec,proto3" json:"spec,omitempty"`
 	// Recommendation on whether this image should be exempt from garbage collection.
-	// It must only be treated as a recommendation--the client can still request the image be deleted,
+	// It must only be treated as a recommendation -- the client can still request that the image be deleted,
 	// and the runtime must oblige.
 	Pinned               bool     `protobuf:"varint,8,opt,name=pinned,proto3" json:"pinned,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`

staging/src/k8s.io/cri-api/pkg/apis/runtime/v1alpha2/api.proto

@@ -1256,7 +1256,7 @@ message Image {
     // ImageSpec for image which includes annotations
     ImageSpec spec = 7;
     // Recommendation on whether this image should be exempt from garbage collection.
-    // It must only be treated as a recommendation--the client can still request the image be deleted,
+    // It must only be treated as a recommendation -- the client can still request that the image be deleted,
     // and the runtime must oblige.
     bool pinned = 8;
 }