package docker
import (
"crypto/rand"
"encoding/hex"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"log"
"os"
"os/exec"
"path"
"strings"
"time"
)
type Image struct {
Id string `json:"id"`
Parent string `json:"parent,omitempty"`
Comment string `json:"comment,omitempty"`
Created time.Time `json:"created"`
Container string `json:"container,omitempty"`
ContainerConfig Config `json:"container_config,omitempty"`
DockerVersion string `json:"docker_version,omitempty"`
Author string `json:"author,omitempty"`
graph *Graph
}
func LoadImage(root string) (*Image, error) {
// Load the json data
jsonData, err := ioutil.ReadFile(jsonPath(root))
if err != nil {
return nil, err
}
var img Image
if err := json.Unmarshal(jsonData, &img); err != nil {
return nil, err
}
if err := ValidateId(img.Id); err != nil {
return nil, err
}
// Check that the filesystem layer exists
if stat, err := os.Stat(layerPath(root)); err != nil {
if os.IsNotExist(err) {
return nil, fmt.Errorf("Couldn't load image %s: no filesystem layer", img.Id)
} else {
return nil, err
}
} else if !stat.IsDir() {
return nil, fmt.Errorf("Couldn't load image %s: %s is not a directory", img.Id, layerPath(root))
}
return &img, nil
}
func StoreImage(img *Image, layerData Archive, root string) error {
// Check that root doesn't already exist
if _, err := os.Stat(root); err == nil {
return fmt.Errorf("Image %s already exists", img.Id)
} else if !os.IsNotExist(err) {
return err
}
// Store the layer
layer := layerPath(root)
if err := os.MkdirAll(layer, 0700); err != nil {
return err
}
if err := Untar(layerData, layer); err != nil {
return err
}
// Store the json ball
jsonData, err := json.Marshal(img)
if err != nil {
return err
}
if err := ioutil.WriteFile(jsonPath(root), jsonData, 0600); err != nil {
return err
}
return nil
}
func layerPath(root string) string {
return path.Join(root, "layer")
}
func jsonPath(root string) string {
return path.Join(root, "json")
}
func MountAUFS(ro []string, rw string, target string) error {
// FIXME: Now mount the layers
rwBranch := fmt.Sprintf("%v=rw", rw)
roBranches := ""
for _, layer := range ro {
roBranches += fmt.Sprintf("%v=ro+wh:", layer)
}
branches := fmt.Sprintf("br:%v:%v", rwBranch, roBranches)
//if error, try to load aufs kernel module
if err := mount("none", target, "aufs", 0, branches); err != nil {
log.Printf("Kernel does not support AUFS, trying to load the AUFS module with modprobe...")
if err := exec.Command("modprobe", "aufs").Run(); err != nil {
return fmt.Errorf("Unable to load the AUFS module")
}
log.Printf("...module loaded.")
if err := mount("none", target, "aufs", 0, branches); err != nil {
return fmt.Errorf("Unable to mount using aufs")
}
}
return nil
}
// TarLayer returns a tar archive of the image's filesystem layer.
func (image *Image) TarLayer(compression Compression) (Archive, error) {
layerPath, err := image.layer()
if err != nil {
return nil, err
}
return Tar(layerPath, compression)
}
func (image *Image) Mount(root, rw string) error {
if mounted, err := Mounted(root); err != nil {
return err
} else if mounted {
return fmt.Errorf("%s is already mounted", root)
}
layers, err := image.layers()
if err != nil {
return err
}
// Create the target directories if they don't exist
if err := os.Mkdir(root, 0755); err != nil && !os.IsExist(err) {
return err
}
if err := os.Mkdir(rw, 0755); err != nil && !os.IsExist(err) {
return err
}
if err := MountAUFS(layers, rw, root); err != nil {
return err
}
return nil
}
func (image *Image) Changes(rw string) ([]Change, error) {
layers, err := image.layers()
if err != nil {
return nil, err
}
return Changes(layers, rw)
}
func (image *Image) ShortId() string {
return TruncateId(image.Id)
}
func ValidateId(id string) error {
if id == "" {
return fmt.Errorf("Image id can't be empty")
}
if strings.Contains(id, ":") {
return fmt.Errorf("Invalid character in image id: ':'")
}
return nil
}
func GenerateId() string {
id := make([]byte, 32)
_, err := io.ReadFull(rand.Reader, id)
if err != nil {
panic(err) // This shouldn't happen
}
return hex.EncodeToString(id)
}
// Image includes convenience proxy functions to its graph
// These functions will return an error if the image is not registered
// (ie. if image.graph == nil)
func (img *Image) History() ([]*Image, error) {
var parents []*Image
if err := img.WalkHistory(
func(img *Image) error {
parents = append(parents, img)
return nil
},
); err != nil {
return nil, err
}
return parents, nil
}
// layers returns all the filesystem layers needed to mount an image
// FIXME: @shykes refactor this function with the new error handling
// (I'll do it if I have time tonight, I focus on the rest)
func (img *Image) layers() ([]string, error) {
var list []string
var e error
if err := img.WalkHistory(
func(img *Image) (err error) {
if layer, err := img.layer(); err != nil {
e = err
} else if layer != "" {
list = append(list, layer)
}
return err
},
); err != nil {
return nil, err
} else if e != nil { // Did an error occur inside the handler?
return nil, e
}
if len(list) == 0 {
return nil, fmt.Errorf("No layer found for image %s\n", img.Id)
}
return list, nil
}
func (img *Image) WalkHistory(handler func(*Image) error) (err error) {
currentImg := img
for currentImg != nil {
if handler != nil {
if err := handler(currentImg); err != nil {
return err
}
}
currentImg, err = currentImg.GetParent()
if err != nil {
return fmt.Errorf("Error while getting parent image: %v", err)
}
}
return nil
}
func (img *Image) GetParent() (*Image, error) {
if img.Parent == "" {
return nil, nil
}
if img.graph == nil {
return nil, fmt.Errorf("Can't lookup parent of unregistered image")
}
return img.graph.Get(img.Parent)
}
func (img *Image) root() (string, error) {
if img.graph == nil {
return "", fmt.Errorf("Can't lookup root of unregistered image")
}
return img.graph.imageRoot(img.Id), nil
}
// Return the path of an image's layer
func (img *Image) layer() (string, error) {
root, err := img.root()
if err != nil {
return "", err
}
return layerPath(root), nil
}