docker/graph: a store for filesystem images and the graph of their relationships

This commit is contained in:
Solomon Hykes 2013-03-18 00:15:35 -07:00
parent 1480bff3a9
commit 33f6a0aaf5
8 changed files with 643 additions and 4 deletions

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@ -1,4 +1,4 @@
package fs
package graph
import (
"errors"
@ -7,6 +7,8 @@ import (
"os/exec"
)
type Archive io.Reader
type Compression uint32
const (

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@ -1,4 +1,4 @@
package fs
package graph
import (
"io/ioutil"

106
graph/changes.go Normal file
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@ -0,0 +1,106 @@
package graph
import (
"fmt"
"os"
"path/filepath"
"strings"
)
type ChangeType int
const (
ChangeModify = iota
ChangeAdd
ChangeDelete
)
type Change struct {
Path string
Kind ChangeType
}
func (change *Change) String() string {
var kind string
switch change.Kind {
case ChangeModify:
kind = "C"
case ChangeAdd:
kind = "A"
case ChangeDelete:
kind = "D"
}
return fmt.Sprintf("%s %s", kind, change.Path)
}
func Changes(layers []string, rw string) ([]Change, error) {
var changes []Change
err := filepath.Walk(rw, func(path string, f os.FileInfo, err error) error {
if err != nil {
return err
}
// Rebase path
path, err = filepath.Rel(rw, path)
if err != nil {
return err
}
path = filepath.Join("/", path)
// Skip root
if path == "/" {
return nil
}
// Skip AUFS metadata
if matched, err := filepath.Match("/.wh..wh.*", path); err != nil || matched {
return err
}
change := Change{
Path: path,
}
// Find out what kind of modification happened
file := filepath.Base(path)
// If there is a whiteout, then the file was removed
if strings.HasPrefix(file, ".wh.") {
originalFile := strings.TrimLeft(file, ".wh.")
change.Path = filepath.Join(filepath.Dir(path), originalFile)
change.Kind = ChangeDelete
} else {
// Otherwise, the file was added
change.Kind = ChangeAdd
// ...Unless it already existed in a top layer, in which case, it's a modification
for _, layer := range layers {
stat, err := os.Stat(filepath.Join(layer, path))
if err != nil && !os.IsNotExist(err) {
return err
}
if err == nil {
// The file existed in the top layer, so that's a modification
// However, if it's a directory, maybe it wasn't actually modified.
// If you modify /foo/bar/baz, then /foo will be part of the changed files only because it's the parent of bar
if stat.IsDir() && f.IsDir() {
if f.Size() == stat.Size() && f.Mode() == stat.Mode() && f.ModTime() == stat.ModTime() {
// Both directories are the same, don't record the change
return nil
}
}
change.Kind = ChangeModify
break
}
}
}
// Record change
changes = append(changes, change)
return nil
})
if err != nil {
return nil, err
}
return changes, nil
}

143
graph/graph.go Normal file
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@ -0,0 +1,143 @@
package graph
import (
"fmt"
"io/ioutil"
"os"
"path"
"path/filepath"
"time"
)
type Graph struct {
Root string
}
func New(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.Mkdir(root, 0700); err != nil && !os.IsExist(err) {
return nil, err
}
return &Graph{
Root: abspath,
}, nil
}
func (graph *Graph) Exists(id string) bool {
if _, err := graph.Get(id); err != nil {
return false
}
return true
}
func (graph *Graph) Get(id string) (*Image, 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)
}
return img, nil
}
func (graph *Graph) Create(layerData Archive, parent, comment string) (*Image, error) {
img := &Image{
Id: GenerateId(),
Parent: parent,
Comment: comment,
Created: time.Now(),
}
if err := graph.Register(layerData, img); err != nil {
return nil, err
}
return img, nil
}
func (graph *Graph) Register(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(img.Id)
defer os.RemoveAll(tmp)
if err != nil {
return fmt.Errorf("Mktemp failed: %s", err)
}
if err := StoreImage(img, layerData, tmp); err != nil {
return err
}
// Commit
if err := os.Rename(tmp, graph.imageRoot(img.Id)); err != nil {
return err
}
img.graph = graph
return nil
}
func (graph *Graph) Mktemp(id string) (string, error) {
tmp, err := New(path.Join(graph.Root, ":tmp:"))
if err != nil {
return "", fmt.Errorf("Couldn't create temp: %s", err)
}
if tmp.Exists(id) {
return "", fmt.Errorf("Image %d already exists", id)
}
return tmp.imageRoot(id), nil
}
func (graph *Graph) Garbage() (*Graph, error) {
return New(path.Join(graph.Root, ":garbage:"))
}
func (graph *Graph) Delete(id string) error {
garbage, err := graph.Garbage()
if err != nil {
return err
}
return os.Rename(graph.imageRoot(id), garbage.imageRoot(id))
}
func (graph *Graph) Undelete(id string) error {
garbage, err := graph.Garbage()
if err != nil {
return err
}
return os.Rename(garbage.imageRoot(id), graph.imageRoot(id))
}
func (graph *Graph) GarbageCollect() error {
garbage, err := graph.Garbage()
if err != nil {
return err
}
return os.RemoveAll(garbage.Root)
}
func (graph *Graph) All() ([]*Image, error) {
files, err := ioutil.ReadDir(graph.Root)
if err != nil {
return nil, err
}
var images []*Image
for _, st := range files {
if img, err := graph.Get(st.Name()); err != nil {
// Skip image
continue
} else {
images = append(images, img)
}
}
return images, nil
}
func (graph *Graph) imageRoot(id string) string {
return path.Join(graph.Root, id)
}

143
graph/graph_test.go Normal file
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@ -0,0 +1,143 @@
package graph
import (
"github.com/dotcloud/docker/fake"
"io/ioutil"
"os"
"path"
"testing"
"time"
)
func TestInit(t *testing.T) {
graph := tempGraph(t)
defer os.RemoveAll(graph.Root)
// Root should exist
if _, err := os.Stat(graph.Root); err != nil {
t.Fatal(err)
}
// All() should be empty
if l, err := graph.All(); err != nil {
t.Fatal(err)
} else if len(l) != 0 {
t.Fatalf("List() should return %d, not %d", 0, len(l))
}
}
// FIXME: Do more extensive tests (ex: create multiple, delete, recreate;
// create multiple, check the amount of images and paths, etc..)
func TestCreate(t *testing.T) {
graph := tempGraph(t)
defer os.RemoveAll(graph.Root)
archive, err := fake.FakeTar()
if err != nil {
t.Fatal(err)
}
image, err := graph.Create(archive, "", "Testing")
if err != nil {
t.Fatal(err)
}
if err := ValidateId(image.Id); err != nil {
t.Fatal(err)
}
if image.Comment != "Testing" {
t.Fatalf("Wrong comment: should be '%s', not '%s'", "Testing", image.Comment)
}
if images, err := graph.All(); err != nil {
t.Fatal(err)
} else if l := len(images); l != 1 {
t.Fatalf("Wrong number of images. Should be %d, not %d", 1, l)
}
}
func TestRegister(t *testing.T) {
graph := tempGraph(t)
defer os.RemoveAll(graph.Root)
archive, err := fake.FakeTar()
if err != nil {
t.Fatal(err)
}
image := &Image{
Id: GenerateId(),
Comment: "testing",
Created: time.Now(),
}
err = graph.Register(archive, image)
if err != nil {
t.Fatal(err)
}
if images, err := graph.All(); err != nil {
t.Fatal(err)
} else if l := len(images); l != 1 {
t.Fatalf("Wrong number of images. Should be %d, not %d", 1, l)
}
if resultImg, err := graph.Get(image.Id); err != nil {
t.Fatal(err)
} else {
if resultImg.Id != image.Id {
t.Fatalf("Wrong image ID. Should be '%s', not '%s'", image.Id, resultImg.Id)
}
if resultImg.Comment != image.Comment {
t.Fatalf("Wrong image comment. Should be '%s', not '%s'", image.Comment, resultImg.Comment)
}
}
}
func TestMount(t *testing.T) {
graph := tempGraph(t)
defer os.RemoveAll(graph.Root)
archive, err := fake.FakeTar()
if err != nil {
t.Fatal(err)
}
image, err := graph.Create(archive, "", "Testing")
if err != nil {
t.Fatal(err)
}
tmp, err := ioutil.TempDir("", "docker-test-graph-mount-")
if err != nil {
t.Fatal(err)
}
defer os.RemoveAll(tmp)
rootfs := path.Join(tmp, "rootfs")
if err := os.MkdirAll(rootfs, 0700); err != nil {
t.Fatal(err)
}
rw := path.Join(tmp, "rw")
if err := os.MkdirAll(rw, 0700); err != nil {
t.Fatal(err)
}
if err := image.Mount(rootfs, rw); err != nil {
t.Fatal(err)
}
// FIXME: test for mount contents
defer func() {
if err := Unmount(rootfs); err != nil {
t.Error(err)
}
}()
}
/*
* HELPER FUNCTIONS
*/
func tempGraph(t *testing.T) *Graph {
tmp, err := ioutil.TempDir("", "docker-graph-")
if err != nil {
t.Fatal(err)
}
graph, err := New(tmp)
if err != nil {
t.Fatal(err)
}
return graph
}
func testArchive(t *testing.T) Archive {
archive, err := fake.FakeTar()
if err != nil {
t.Fatal(err)
}
return archive
}

245
graph/image.go Normal file
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@ -0,0 +1,245 @@
package graph
import (
"encoding/json"
"fmt"
"github.com/dotcloud/docker/future"
"io/ioutil"
"os"
"path"
"strings"
"syscall"
"time"
)
type Image struct {
Id string
Parent string
Comment string
Created time.Time
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:", layer)
}
branches := fmt.Sprintf("br:%v:%v", rwBranch, roBranches)
return mount("none", target, "aufs", 0, branches)
}
func Unmount(target string) error {
if err := syscall.Unmount(target, 0); err != nil {
return err
}
// Even though we just unmounted the filesystem, AUFS will prevent deleting the mntpoint
// for some time. We'll just keep retrying until it succeeds.
for retries := 0; retries < 1000; retries++ {
err := os.Remove(target)
if err == nil {
// rm mntpoint succeeded
return nil
}
if os.IsNotExist(err) {
// mntpoint doesn't exist anymore. Success.
return nil
}
// fmt.Printf("(%v) Remove %v returned: %v\n", retries, target, err)
time.Sleep(10 * time.Millisecond)
}
return fmt.Errorf("Umount: Failed to umount %v", target)
}
func (image *Image) Mount(root, rw string) error {
layers, err := image.layers()
if err != nil {
return err
}
// FIXME: @creack shouldn't we do this after going over changes?
if err := MountAUFS(layers, rw, root); err != nil {
return err
}
// FIXME: Create tests for deletion
// FIXME: move this part to change.go
// Retrieve the changeset from the parent and apply it to the container
// - Retrieve the changes
changes, err := Changes(layers, layers[0])
if err != nil {
return err
}
// Iterate on changes
for _, c := range changes {
// If there is a delete
if c.Kind == ChangeDelete {
// Make sure the directory exists
file_path, file_name := path.Dir(c.Path), path.Base(c.Path)
if err := os.MkdirAll(path.Join(rw, file_path), 0755); err != nil {
return err
}
// And create the whiteout (we just need to create empty file, discard the return)
if _, err := os.Create(path.Join(path.Join(rw, file_path),
".wh."+path.Base(file_name))); err != nil {
return err
}
}
}
return nil
}
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 {
future.Seed()
return future.RandomId()
}
// 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) {
parents = append(parents, img)
},
); err != nil {
return nil, err
}
return parents, nil
}
// layers returns all the filesystem layers needed to mount an image
func (img *Image) layers() ([]string, error) {
var list []string
var e error
if err := img.WalkHistory(
func(img *Image) {
if layer, err := img.layer(); err != nil {
e = err
} else if layer != "" {
list = append(list, layer)
}
},
); 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 {
var err error
currentImg := img
for currentImg != nil {
if handler != nil {
handler(currentImg)
}
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
}

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package fs
package graph
import "errors"

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@ -1,4 +1,4 @@
package fs
package graph
import "syscall"