package docker import ( "fmt" "github.com/dotcloud/docker/utils" "io" "io/ioutil" "os" "path" "path/filepath" "strings" "time" ) // A Graph is a store for versioned filesystem images and the relationship between them. type Graph struct { Root string idIndex *utils.TruncIndex } // 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) (*Graph, error) { abspath, err := filepath.Abs(root) if err != nil { return nil, err } // Create the root directory if it doesn't exists if err := os.MkdirAll(root, 0700); err != nil && !os.IsExist(err) { return nil, err } graph := &Graph{ Root: abspath, idIndex: utils.NewTruncIndex(), } if err := graph.restore(); err != nil { return nil, err } return graph, nil } func (graph *Graph) restore() error { dir, err := ioutil.ReadDir(graph.Root) if err != nil { return err } for _, v := range dir { id := v.Name() graph.idIndex.Add(id) } 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) bool { return err != nil && (strings.Contains(err.Error(), "does not exist") || strings.Contains(err.Error(), "No such")) } // 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, error) { id, err := graph.idIndex.Get(name) if err != nil { return nil, err } // FIXME: return nil when the image doesn't exist, instead of an error img, err := LoadImage(graph.imageRoot(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) } img.graph = graph if img.Size == 0 { root, err := img.root() if err != nil { return nil, err } if err := StoreSize(img, root); 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, container *Container, comment, author string, config *Config) (*Image, error) { img := &Image{ ID: GenerateID(), Comment: comment, Created: time.Now(), DockerVersion: VERSION, Author: author, Config: config, Architecture: "x86_64", } if container != nil { img.Parent = container.Image img.Container = container.ID img.ContainerConfig = *container.Config } if err := graph.Register(nil, layerData, img); err != nil { return nil, err } return img, nil } // Register imports a pre-existing image into the graph. // FIXME: pass img as first argument func (graph *Graph) Register(jsonData []byte, layerData Archive, img *Image) error { if err := ValidateID(img.ID); err != nil { return err } // (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) } tmp, err := graph.Mktemp("") defer os.RemoveAll(tmp) if err != nil { return fmt.Errorf("Mktemp failed: %s", err) } if err := StoreImage(img, jsonData, layerData, tmp); err != nil { return err } // Commit if err := os.Rename(tmp, graph.imageRoot(img.ID)); err != nil { return err } img.graph = graph 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. // FIXME: does this belong in Graph? How about MktempFile, let the caller use it for archives? func (graph *Graph) TempLayerArchive(id string, compression Compression, sf *utils.StreamFormatter, output io.Writer) (*TempArchive, error) { image, err := graph.Get(id) if err != nil { return nil, err } tmp, err := graph.tmp() if err != nil { return nil, err } archive, err := image.TarLayer(compression) if err != nil { return nil, err } return NewTempArchive(utils.ProgressReader(ioutil.NopCloser(archive), 0, output, sf.FormatProgress("", "Buffering to disk", "%v/%v (%v)"), sf, true), tmp.Root) } // Mktemp creates a temporary sub-directory inside the graph's filesystem. func (graph *Graph) Mktemp(id string) (string, error) { if id == "" { id = GenerateID() } tmp, err := graph.tmp() if err != nil { return "", fmt.Errorf("Couldn't create temp: %s", err) } if tmp.Exists(id) { return "", fmt.Errorf("Image %s already exists", id) } return tmp.imageRoot(id), nil } // getDockerInitLayer returns the path of a layer containing a mountpoint suitable // for bind-mounting dockerinit into the container. The mountpoint is simply an // empty file at /.dockerinit // // This extra layer is used by all containers as the top-most ro layer. It protects // the container from unwanted side-effects on the rw layer. func (graph *Graph) getDockerInitLayer() (string, error) { tmp, err := graph.tmp() if err != nil { return "", err } initLayer := tmp.imageRoot("_dockerinit") if err := os.Mkdir(initLayer, 0755); err != nil && !os.IsExist(err) { // If directory already existed, keep going. // For all other errors, abort. return "", err } // FIXME: how the hell do I break down this line in a way // that is idiomatic and not ugly as hell? if f, err := os.OpenFile(path.Join(initLayer, ".dockerinit"), os.O_CREATE|os.O_TRUNC, 0700); err != nil && !os.IsExist(err) { // If file already existed, keep going. // For all other errors, abort. return "", err } else { f.Close() } // Layer is ready to use, if it wasn't before. return initLayer, nil } func (graph *Graph) tmp() (*Graph, error) { // Changed to _tmp from :tmp:, because it messed with ":" separators in aufs branch syntax... return NewGraph(path.Join(graph.Root, "_tmp")) } // Check if given error is "not empty". // Note: this is the way golang does it internally with os.IsNotExists. func isNotEmpty(err error) bool { switch pe := err.(type) { case nil: return false case *os.PathError: err = pe.Err case *os.LinkError: err = pe.Err } return strings.Contains(err.Error(), " not empty") } // 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("") if err != nil { return err } graph.idIndex.Delete(id) err = os.Rename(graph.imageRoot(id), tmp) if err != nil { return err } return os.RemoveAll(tmp) } // Map returns a list of all images in the graph, addressable by ID. func (graph *Graph) Map() (map[string]*Image, error) { // FIXME: this should replace All() all, err := graph.All() if err != nil { return nil, err } images := make(map[string]*Image, len(all)) for _, image := range all { images[image.ID] = image } return images, nil } // All returns a list of all images in the graph. func (graph *Graph) All() ([]*Image, error) { var images []*Image err := graph.WalkAll(func(image *Image) { images = append(images, image) }) return images, err } // 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)) error { files, err := ioutil.ReadDir(graph.Root) if err != nil { return err } for _, st := range files { if img, err := graph.Get(st.Name()); err != nil { // Skip image continue } else if handler != nil { handler(img) } } return nil } // 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, error) { byParent := make(map[string][]*Image) err := graph.WalkAll(func(image *Image) { parent, err := graph.Get(image.Parent) if err != nil { return } if children, exists := byParent[parent.ID]; exists { byParent[parent.ID] = []*Image{image} } else { byParent[parent.ID] = append(children, image) } }) return byParent, err } // 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, error) { heads := make(map[string]*Image) byParent, err := graph.ByParent() if err != nil { return nil, err } err = graph.WalkAll(func(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, err } func (graph *Graph) imageRoot(id string) string { return path.Join(graph.Root, id) }