package cache import ( "encoding/json" "fmt" "reflect" "strings" containertypes "github.com/docker/docker/api/types/container" "github.com/docker/docker/dockerversion" "github.com/docker/docker/image" "github.com/docker/docker/layer" "github.com/pkg/errors" ) // NewLocal returns a local image cache, based on parent chain func NewLocal(store image.Store) *LocalImageCache { return &LocalImageCache{ store: store, } } // LocalImageCache is cache based on parent chain. type LocalImageCache struct { store image.Store } // GetCache returns the image id found in the cache func (lic *LocalImageCache) GetCache(imgID string, config *containertypes.Config) (string, error) { return getImageIDAndError(getLocalCachedImage(lic.store, image.ID(imgID), config)) } // New returns an image cache, based on history objects func New(store image.Store) *ImageCache { return &ImageCache{ store: store, localImageCache: NewLocal(store), } } // ImageCache is cache based on history objects. Requires initial set of images. type ImageCache struct { sources []*image.Image store image.Store localImageCache *LocalImageCache } // Populate adds an image to the cache (to be queried later) func (ic *ImageCache) Populate(image *image.Image) { ic.sources = append(ic.sources, image) } // GetCache returns the image id found in the cache func (ic *ImageCache) GetCache(parentID string, cfg *containertypes.Config) (string, error) { imgID, err := ic.localImageCache.GetCache(parentID, cfg) if err != nil { return "", err } if imgID != "" { for _, s := range ic.sources { if ic.isParent(s.ID(), image.ID(imgID)) { return imgID, nil } } } var parent *image.Image lenHistory := 0 if parentID != "" { parent, err = ic.store.Get(image.ID(parentID)) if err != nil { return "", errors.Wrapf(err, "unable to find image %v", parentID) } lenHistory = len(parent.History) } for _, target := range ic.sources { if !isValidParent(target, parent) || !isValidConfig(cfg, target.History[lenHistory]) { continue } if len(target.History)-1 == lenHistory { // last if parent != nil { if err := ic.store.SetParent(target.ID(), parent.ID()); err != nil { return "", errors.Wrapf(err, "failed to set parent for %v to %v", target.ID(), parent.ID()) } } return target.ID().String(), nil } imgID, err := ic.restoreCachedImage(parent, target, cfg) if err != nil { return "", errors.Wrapf(err, "failed to restore cached image from %q to %v", parentID, target.ID()) } ic.sources = []*image.Image{target} // avoid jumping to different target, tuned for safety atm return imgID.String(), nil } return "", nil } func (ic *ImageCache) restoreCachedImage(parent, target *image.Image, cfg *containertypes.Config) (image.ID, error) { var history []image.History rootFS := image.NewRootFS() lenHistory := 0 if parent != nil { history = parent.History rootFS = parent.RootFS lenHistory = len(parent.History) } history = append(history, target.History[lenHistory]) if layer := getLayerForHistoryIndex(target, lenHistory); layer != "" { rootFS.Append(layer) } config, err := json.Marshal(&image.Image{ V1Image: image.V1Image{ DockerVersion: dockerversion.Version, Config: cfg, Architecture: target.Architecture, OS: target.OS, Author: target.Author, Created: history[len(history)-1].Created, }, RootFS: rootFS, History: history, OSFeatures: target.OSFeatures, OSVersion: target.OSVersion, }) if err != nil { return "", errors.Wrap(err, "failed to marshal image config") } imgID, err := ic.store.Create(config) if err != nil { return "", errors.Wrap(err, "failed to create cache image") } if parent != nil { if err := ic.store.SetParent(imgID, parent.ID()); err != nil { return "", errors.Wrapf(err, "failed to set parent for %v to %v", target.ID(), parent.ID()) } } return imgID, nil } func (ic *ImageCache) isParent(imgID, parentID image.ID) bool { nextParent, err := ic.store.GetParent(imgID) if err != nil { return false } if nextParent == parentID { return true } return ic.isParent(nextParent, parentID) } func getLayerForHistoryIndex(image *image.Image, index int) layer.DiffID { layerIndex := 0 for i, h := range image.History { if i == index { if h.EmptyLayer { return "" } break } if !h.EmptyLayer { layerIndex++ } } return image.RootFS.DiffIDs[layerIndex] // validate? } func isValidConfig(cfg *containertypes.Config, h image.History) bool { // todo: make this format better than join that loses data return strings.Join(cfg.Cmd, " ") == h.CreatedBy } func isValidParent(img, parent *image.Image) bool { if len(img.History) == 0 { return false } if parent == nil || len(parent.History) == 0 && len(parent.RootFS.DiffIDs) == 0 { return true } if len(parent.History) >= len(img.History) { return false } if len(parent.RootFS.DiffIDs) > len(img.RootFS.DiffIDs) { return false } for i, h := range parent.History { if !reflect.DeepEqual(h, img.History[i]) { return false } } for i, d := range parent.RootFS.DiffIDs { if d != img.RootFS.DiffIDs[i] { return false } } return true } func getImageIDAndError(img *image.Image, err error) (string, error) { if img == nil || err != nil { return "", err } return img.ID().String(), nil } // getLocalCachedImage returns the most recent created image that is a child // of the image with imgID, that had the same config when it was // created. nil is returned if a child cannot be found. An error is // returned if the parent image cannot be found. func getLocalCachedImage(imageStore image.Store, imgID image.ID, config *containertypes.Config) (*image.Image, error) { // Loop on the children of the given image and check the config getMatch := func(siblings []image.ID) (*image.Image, error) { var match *image.Image for _, id := range siblings { img, err := imageStore.Get(id) if err != nil { return nil, fmt.Errorf("unable to find image %q", id) } if compare(&img.ContainerConfig, config) { // check for the most up to date match if match == nil || match.Created.Before(img.Created) { match = img } } } return match, nil } // In this case, this is `FROM scratch`, which isn't an actual image. if imgID == "" { images := imageStore.Map() var siblings []image.ID for id, img := range images { if img.Parent == imgID { siblings = append(siblings, id) } } return getMatch(siblings) } // find match from child images siblings := imageStore.Children(imgID) return getMatch(siblings) }