package docker
import (
"fmt"
"github.com/dotcloud/docker/archive"
"github.com/dotcloud/docker/graphdriver"
"github.com/dotcloud/docker/utils"
"io"
"io/ioutil"
"os"
"path"
"path/filepath"
"runtime"
"strings"
"syscall"
"time"
)
// A Graph is a store for versioned filesystem images and the relationship between them.
type Graph struct {
Root string
idIndex *utils.TruncIndex
driver graphdriver.Driver
}
// 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 := os.MkdirAll(root, 0700); err != nil && !os.IsExist(err) {
return nil, err
}
graph := &Graph{
Root: abspath,
idIndex: utils.NewTruncIndex(),
driver: driver,
}
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()
if graph.driver.Exists(id) {
graph.idIndex.Add(id)
}
}
utils.Debugf("Restored %d elements", len(dir))
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
}
// Check that the filesystem layer exists
rootfs, err := graph.driver.Get(img.ID)
if err != nil {
return nil, fmt.Errorf("Driver %s failed to get image rootfs %s: %s", graph.driver, img.ID, 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 {
var size int64
if img.Parent == "" {
if size, err = utils.TreeSize(rootfs); err != nil {
return nil, err
}
} else {
parentFs, err := graph.driver.Get(img.Parent)
if err != nil {
return nil, err
}
changes, err := archive.ChangesDirs(rootfs, parentFs)
if err != nil {
return nil, err
}
size = archive.ChangesSize(rootfs, changes)
}
img.Size = size
if err := img.SaveSize(graph.imageRoot(id)); 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.Archive, container *Container, comment, author string, config *Config) (*Image, error) {
img := &Image{
ID: GenerateID(),
Comment: comment,
Created: time.Now().UTC(),
DockerVersion: VERSION,
Author: author,
Config: config,
Architecture: runtime.GOARCH,
OS: runtime.GOOS,
}
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.Archive, img *Image) (err error) {
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.
// FIXME: this leaves a possible race condition.
if err != nil {
graph.driver.Remove(img.ID)
}
}()
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)
}
// 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 := graph.driver.Create(img.ID, img.Parent); err != nil {
return fmt.Errorf("Driver %s failed to create image rootfs %s: %s", graph.driver, img.ID, err)
}
// Mount the root filesystem so we can apply the diff/layer
rootfs, err := graph.driver.Get(img.ID)
if err != nil {
return fmt.Errorf("Driver %s failed to get image rootfs %s: %s", graph.driver, img.ID, err)
}
img.graph = graph
if err := StoreImage(img, jsonData, layerData, tmp, rootfs); 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.
// FIXME: does this belong in Graph? How about MktempFile, let the caller use it for archives?
func (graph *Graph) TempLayerArchive(id string, compression archive.Compression, sf *utils.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 := image.TarLayer()
if err != nil {
return nil, err
}
return archive.NewTempArchive(utils.ProgressReader(ioutil.NopCloser(a), 0, output, sf, false, utils.TruncateID(id), "Buffering to disk"), tmp)
}
// Mktemp creates a temporary sub-directory inside the graph's filesystem.
func (graph *Graph) Mktemp(id string) (string, error) {
dir := path.Join(graph.Root, "_tmp", GenerateID())
if err := os.MkdirAll(dir, 0700); err != nil {
return "", err
}
return dir, nil
}
// setupInitLayer populates a directory with mountpoints 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 setupInitLayer(initLayer string) error {
for pth, typ := range map[string]string{
"/dev/pts": "dir",
"/dev/shm": "dir",
"/proc": "dir",
"/sys": "dir",
"/.dockerinit": "file",
"/.dockerenv": "file",
"/etc/resolv.conf": "file",
"/etc/hosts": "file",
"/etc/hostname": "file",
// "var/run": "dir",
// "var/lock": "dir",
} {
parts := strings.Split(pth, "/")
prev := "/"
for _, p := range parts[1:] {
prev = path.Join(prev, p)
syscall.Unlink(path.Join(initLayer, prev))
}
if _, err := os.Stat(path.Join(initLayer, pth)); err != nil {
if os.IsNotExist(err) {
switch typ {
case "dir":
if err := os.MkdirAll(path.Join(initLayer, pth), 0755); err != nil {
return err
}
case "file":
if err := os.MkdirAll(path.Join(initLayer, path.Dir(pth)), 0755); err != nil {
return err
}
f, err := os.OpenFile(path.Join(initLayer, pth), os.O_CREATE, 0755)
if err != nil {
return err
}
f.Close()
}
} else {
return err
}
}
}
// Layer is ready to use, if it wasn't before.
return nil
}
// 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
}
// 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, error) {
images := make(map[string]*Image)
err := graph.walkAll(func(image *Image) {
images[image.ID] = image
})
if err != nil {
return nil, err
}
return images, nil
}
// 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] = append(children, image)
} else {
byParent[parent.ID] = []*Image{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)
}
func (graph *Graph) Driver() graphdriver.Driver {
return graph.driver
}