package graph import ( "compress/gzip" "crypto/sha256" "encoding/json" "errors" "fmt" "io" "io/ioutil" "os" "path/filepath" "runtime" "strconv" "strings" "sync" "time" "github.com/Sirupsen/logrus" "github.com/docker/distribution/digest" "github.com/docker/docker/autogen/dockerversion" "github.com/docker/docker/daemon/graphdriver" "github.com/docker/docker/image" "github.com/docker/docker/pkg/archive" "github.com/docker/docker/pkg/progressreader" "github.com/docker/docker/pkg/streamformatter" "github.com/docker/docker/pkg/stringid" "github.com/docker/docker/pkg/system" "github.com/docker/docker/pkg/truncindex" "github.com/docker/docker/runconfig" ) // The type is used to protect pulling or building related image // layers from deleteing when filtered by dangling=true // The key of layers is the images ID which is pulling or building // The value of layers is a slice which hold layer IDs referenced to // pulling or building images type retainedLayers struct { layerHolders map[string]map[string]struct{} // map[layerID]map[sessionID] sync.Mutex } func (r *retainedLayers) Add(sessionID string, layerIDs []string) { r.Lock() defer r.Unlock() for _, layerID := range layerIDs { if r.layerHolders[layerID] == nil { r.layerHolders[layerID] = map[string]struct{}{} } r.layerHolders[layerID][sessionID] = struct{}{} } } func (r *retainedLayers) Delete(sessionID string, layerIDs []string) { r.Lock() defer r.Unlock() for _, layerID := range layerIDs { holders, ok := r.layerHolders[layerID] if !ok { continue } delete(holders, sessionID) if len(holders) == 0 { delete(r.layerHolders, layerID) // Delete any empty reference set. } } } func (r *retainedLayers) Exists(layerID string) bool { r.Lock() _, exists := r.layerHolders[layerID] r.Unlock() return exists } // A Graph is a store for versioned filesystem images and the relationship between them. type Graph struct { root string idIndex *truncindex.TruncIndex driver graphdriver.Driver imageMutex imageMutex // protect images in driver. retained *retainedLayers } var ( // ErrDigestNotSet is used when request the digest for a layer // but the layer has no digest value or content to compute the // the digest. ErrDigestNotSet = errors.New("digest is not set for layer") ) // NewGraph instantiates a new graph at the given root path in the filesystem. // `root` will be created if it doesn't exist. func NewGraph(root string, driver graphdriver.Driver) (*Graph, error) { abspath, err := filepath.Abs(root) if err != nil { return nil, err } // Create the root directory if it doesn't exists if err := system.MkdirAll(root, 0700); err != nil && !os.IsExist(err) { return nil, err } graph := &Graph{ root: abspath, idIndex: truncindex.NewTruncIndex([]string{}), driver: driver, retained: &retainedLayers{layerHolders: make(map[string]map[string]struct{})}, } if err := graph.restore(); err != nil { return nil, err } return graph, nil } // IsHeld returns whether the given layerID is being used by an ongoing pull or build. func (graph *Graph) IsHeld(layerID string) bool { return graph.retained.Exists(layerID) } func (graph *Graph) restore() error { dir, err := ioutil.ReadDir(graph.root) if err != nil { return err } var ids = []string{} for _, v := range dir { id := v.Name() if graph.driver.Exists(id) { ids = append(ids, id) } } baseIds, err := graph.restoreBaseImages() if err != nil { return err } ids = append(ids, baseIds...) graph.idIndex = truncindex.NewTruncIndex(ids) logrus.Debugf("Restored %d elements", len(ids)) return nil } // FIXME: Implement error subclass instead of looking at the error text // Note: This is the way golang implements os.IsNotExists on Plan9 func (graph *Graph) IsNotExist(err error, id string) bool { return err != nil && (strings.Contains(strings.ToLower(err.Error()), "does not exist") || strings.Contains(strings.ToLower(err.Error()), "no such")) && strings.Contains(err.Error(), id) } // Exists returns true if an image is registered at the given id. // If the image doesn't exist or if an error is encountered, false is returned. func (graph *Graph) Exists(id string) bool { if _, err := graph.Get(id); err != nil { return false } return true } // Get returns the image with the given id, or an error if the image doesn't exist. func (graph *Graph) Get(name string) (*image.Image, error) { id, err := graph.idIndex.Get(name) if err != nil { return nil, fmt.Errorf("could not find image: %v", err) } img, err := graph.loadImage(id) if err != nil { return nil, err } if img.ID != id { return nil, fmt.Errorf("Image stored at '%s' has wrong id '%s'", id, img.ID) } if img.Size < 0 { size, err := graph.driver.DiffSize(img.ID, img.Parent) if err != nil { return nil, fmt.Errorf("unable to calculate size of image id %q: %s", img.ID, err) } img.Size = size if err := graph.saveSize(graph.imageRoot(id), int(img.Size)); err != nil { return nil, err } } return img, nil } // Create creates a new image and registers it in the graph. func (graph *Graph) Create(layerData archive.ArchiveReader, containerID, containerImage, comment, author string, containerConfig, config *runconfig.Config) (*image.Image, error) { img := &image.Image{ ID: stringid.GenerateRandomID(), Comment: comment, Created: time.Now().UTC(), DockerVersion: dockerversion.VERSION, Author: author, Config: config, Architecture: runtime.GOARCH, OS: runtime.GOOS, } if containerID != "" { img.Parent = containerImage img.Container = containerID img.ContainerConfig = *containerConfig } if err := graph.Register(img, layerData); err != nil { return nil, err } return img, nil } // Register imports a pre-existing image into the graph. func (graph *Graph) Register(img *image.Image, layerData archive.ArchiveReader) (err error) { if err := image.ValidateID(img.ID); err != nil { return err } // We need this entire operation to be atomic within the engine. Note that // this doesn't mean Register is fully safe yet. graph.imageMutex.Lock(img.ID) defer graph.imageMutex.Unlock(img.ID) // The returned `error` must be named in this function's signature so that // `err` is not shadowed in this deferred cleanup. defer func() { // If any error occurs, remove the new dir from the driver. // Don't check for errors since the dir might not have been created. if err != nil { graph.driver.Remove(img.ID) } }() // (This is a convenience to save time. Race conditions are taken care of by os.Rename) if graph.Exists(img.ID) { return fmt.Errorf("Image %s already exists", img.ID) } // Ensure that the image root does not exist on the filesystem // when it is not registered in the graph. // This is common when you switch from one graph driver to another if err := os.RemoveAll(graph.imageRoot(img.ID)); err != nil && !os.IsNotExist(err) { return err } // If the driver has this ID but the graph doesn't, remove it from the driver to start fresh. // (the graph is the source of truth). // Ignore errors, since we don't know if the driver correctly returns ErrNotExist. // (FIXME: make that mandatory for drivers). graph.driver.Remove(img.ID) tmp, err := graph.mktemp("") defer os.RemoveAll(tmp) if err != nil { return fmt.Errorf("mktemp failed: %s", err) } // Create root filesystem in the driver if err := createRootFilesystemInDriver(graph, img, layerData); err != nil { return err } // Apply the diff/layer if err := graph.storeImage(img, layerData, tmp); err != nil { return err } // Commit if err := os.Rename(tmp, graph.imageRoot(img.ID)); err != nil { return err } graph.idIndex.Add(img.ID) return nil } // TempLayerArchive creates a temporary archive of the given image's filesystem layer. // The archive is stored on disk and will be automatically deleted as soon as has been read. // If output is not nil, a human-readable progress bar will be written to it. func (graph *Graph) TempLayerArchive(id string, sf *streamformatter.StreamFormatter, output io.Writer) (*archive.TempArchive, error) { image, err := graph.Get(id) if err != nil { return nil, err } tmp, err := graph.mktemp("") if err != nil { return nil, err } a, err := graph.TarLayer(image) if err != nil { return nil, err } progressReader := progressreader.New(progressreader.Config{ In: a, Out: output, Formatter: sf, Size: 0, NewLines: false, ID: stringid.TruncateID(id), Action: "Buffering to disk", }) defer progressReader.Close() return archive.NewTempArchive(progressReader, tmp) } // mktemp creates a temporary sub-directory inside the graph's filesystem. func (graph *Graph) mktemp(id string) (string, error) { dir := filepath.Join(graph.root, "_tmp", stringid.GenerateRandomID()) if err := system.MkdirAll(dir, 0700); err != nil { return "", err } return dir, nil } func (graph *Graph) newTempFile() (*os.File, error) { tmp, err := graph.mktemp("") if err != nil { return nil, err } return ioutil.TempFile(tmp, "") } func bufferToFile(f *os.File, src io.Reader) (int64, digest.Digest, error) { var ( h = sha256.New() w = gzip.NewWriter(io.MultiWriter(f, h)) ) _, err := io.Copy(w, src) w.Close() if err != nil { return 0, "", err } n, err := f.Seek(0, os.SEEK_CUR) if err != nil { return 0, "", err } if _, err := f.Seek(0, 0); err != nil { return 0, "", err } return n, digest.NewDigest("sha256", h), nil } // Delete atomically removes an image from the graph. func (graph *Graph) Delete(name string) error { id, err := graph.idIndex.Get(name) if err != nil { return err } tmp, err := graph.mktemp("") graph.idIndex.Delete(id) if err == nil { if err := os.Rename(graph.imageRoot(id), tmp); err != nil { // On err make tmp point to old dir and cleanup unused tmp dir os.RemoveAll(tmp) tmp = graph.imageRoot(id) } } else { // On err make tmp point to old dir for cleanup tmp = graph.imageRoot(id) } // Remove rootfs data from the driver graph.driver.Remove(id) // Remove the trashed image directory return os.RemoveAll(tmp) } // Map returns a list of all images in the graph, addressable by ID. func (graph *Graph) Map() map[string]*image.Image { images := make(map[string]*image.Image) graph.walkAll(func(image *image.Image) { images[image.ID] = image }) return images } // walkAll iterates over each image in the graph, and passes it to a handler. // The walking order is undetermined. func (graph *Graph) walkAll(handler func(*image.Image)) { graph.idIndex.Iterate(func(id string) { if img, err := graph.Get(id); err != nil { return } else if handler != nil { handler(img) } }) } // ByParent returns a lookup table of images by their parent. // If an image of id ID has 3 children images, then the value for key ID // will be a list of 3 images. // If an image has no children, it will not have an entry in the table. func (graph *Graph) ByParent() map[string][]*image.Image { byParent := make(map[string][]*image.Image) graph.walkAll(func(img *image.Image) { parent, err := graph.Get(img.Parent) if err != nil { return } if children, exists := byParent[parent.ID]; exists { byParent[parent.ID] = append(children, img) } else { byParent[parent.ID] = []*image.Image{img} } }) return byParent } // If the images and layers are in pulling chain, retain them. // If not, they may be deleted by rmi with dangling condition. func (graph *Graph) Retain(sessionID string, layerIDs ...string) { graph.retained.Add(sessionID, layerIDs) } // Release removes the referenced image id from the provided set of layers. func (graph *Graph) Release(sessionID string, layerIDs ...string) { graph.retained.Delete(sessionID, layerIDs) } // Heads returns all heads in the graph, keyed by id. // A head is an image which is not the parent of another image in the graph. func (graph *Graph) Heads() map[string]*image.Image { heads := make(map[string]*image.Image) byParent := graph.ByParent() graph.walkAll(func(image *image.Image) { // If it's not in the byParent lookup table, then // it's not a parent -> so it's a head! if _, exists := byParent[image.ID]; !exists { heads[image.ID] = image } }) return heads } func (graph *Graph) imageRoot(id string) string { return filepath.Join(graph.root, id) } // loadImage fetches the image with the given id from the graph. func (graph *Graph) loadImage(id string) (*image.Image, error) { root := graph.imageRoot(id) // Open the JSON file to decode by streaming jsonSource, err := os.Open(jsonPath(root)) if err != nil { return nil, err } defer jsonSource.Close() img := &image.Image{} dec := json.NewDecoder(jsonSource) // Decode the JSON data if err := dec.Decode(img); err != nil { return nil, err } if err := image.ValidateID(img.ID); err != nil { return nil, err } if buf, err := ioutil.ReadFile(filepath.Join(root, "layersize")); err != nil { if !os.IsNotExist(err) { return nil, err } // If the layersize file does not exist then set the size to a negative number // because a layer size of 0 (zero) is valid img.Size = -1 } else { // Using Atoi here instead would temporarily convert the size to a machine // dependent integer type, which causes images larger than 2^31 bytes to // display negative sizes on 32-bit machines: size, err := strconv.ParseInt(string(buf), 10, 64) if err != nil { return nil, err } img.Size = int64(size) } return img, nil } // saveSize stores the `size` in the provided graph `img` directory `root`. func (graph *Graph) saveSize(root string, size int) error { if err := ioutil.WriteFile(filepath.Join(root, "layersize"), []byte(strconv.Itoa(size)), 0600); err != nil { return fmt.Errorf("Error storing image size in %s/layersize: %s", root, err) } return nil } // SetDigest sets the digest for the image layer to the provided value. func (graph *Graph) SetDigest(id string, dgst digest.Digest) error { root := graph.imageRoot(id) if err := ioutil.WriteFile(filepath.Join(root, "checksum"), []byte(dgst.String()), 0600); err != nil { return fmt.Errorf("Error storing digest in %s/checksum: %s", root, err) } return nil } // GetDigest gets the digest for the provide image layer id. func (graph *Graph) GetDigest(id string) (digest.Digest, error) { root := graph.imageRoot(id) cs, err := ioutil.ReadFile(filepath.Join(root, "checksum")) if err != nil { if os.IsNotExist(err) { return "", ErrDigestNotSet } return "", err } return digest.ParseDigest(string(cs)) } // RawJSON returns the JSON representation for an image as a byte array. func (graph *Graph) RawJSON(id string) ([]byte, error) { root := graph.imageRoot(id) buf, err := ioutil.ReadFile(jsonPath(root)) if err != nil { return nil, fmt.Errorf("Failed to read json for image %s: %s", id, err) } return buf, nil } func jsonPath(root string) string { return filepath.Join(root, "json") }