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moby--moby/pkg/archive/changes.go
Arnaud Porterie 6a7a7570bb Merge pull request #12833 from burke/faster-changes
Optimize archive.ChangesDirs on Linux
2015-06-12 17:05:34 -07:00

377 lines
9.8 KiB
Go

package archive
import (
"archive/tar"
"bytes"
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"sort"
"strings"
"syscall"
"time"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/pkg/pools"
"github.com/docker/docker/pkg/system"
)
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)
}
// for sort.Sort
type changesByPath []Change
func (c changesByPath) Less(i, j int) bool { return c[i].Path < c[j].Path }
func (c changesByPath) Len() int { return len(c) }
func (c changesByPath) Swap(i, j int) { c[j], c[i] = c[i], c[j] }
// Gnu tar and the go tar writer don't have sub-second mtime
// precision, which is problematic when we apply changes via tar
// files, we handle this by comparing for exact times, *or* same
// second count and either a or b having exactly 0 nanoseconds
func sameFsTime(a, b time.Time) bool {
return a == b ||
(a.Unix() == b.Unix() &&
(a.Nanosecond() == 0 || b.Nanosecond() == 0))
}
func sameFsTimeSpec(a, b syscall.Timespec) bool {
return a.Sec == b.Sec &&
(a.Nsec == b.Nsec || a.Nsec == 0 || b.Nsec == 0)
}
// Changes walks the path rw and determines changes for the files in the path,
// with respect to the parent layers
func Changes(layers []string, rw string) ([]Change, error) {
var (
changes []Change
changedDirs = make(map[string]struct{})
)
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 := file[len(".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() && sameFsTime(f.ModTime(), stat.ModTime()) {
// Both directories are the same, don't record the change
return nil
}
}
change.Kind = ChangeModify
break
}
}
}
// If /foo/bar/file.txt is modified, then /foo/bar must be part of the changed files.
// This block is here to ensure the change is recorded even if the
// modify time, mode and size of the parent directoriy in the rw and ro layers are all equal.
// Check https://github.com/docker/docker/pull/13590 for details.
if f.IsDir() {
changedDirs[path] = struct{}{}
}
if change.Kind == ChangeAdd || change.Kind == ChangeDelete {
parent := filepath.Dir(path)
if _, ok := changedDirs[parent]; !ok && parent != "/" {
changes = append(changes, Change{Path: parent, Kind: ChangeModify})
changedDirs[parent] = struct{}{}
}
}
// Record change
changes = append(changes, change)
return nil
})
if err != nil && !os.IsNotExist(err) {
return nil, err
}
return changes, nil
}
type FileInfo struct {
parent *FileInfo
name string
stat *system.Stat_t
children map[string]*FileInfo
capability []byte
added bool
}
func (root *FileInfo) LookUp(path string) *FileInfo {
parent := root
if path == "/" {
return root
}
pathElements := strings.Split(path, "/")
for _, elem := range pathElements {
if elem != "" {
child := parent.children[elem]
if child == nil {
return nil
}
parent = child
}
}
return parent
}
func (info *FileInfo) path() string {
if info.parent == nil {
return "/"
}
return filepath.Join(info.parent.path(), info.name)
}
func (info *FileInfo) addChanges(oldInfo *FileInfo, changes *[]Change) {
sizeAtEntry := len(*changes)
if oldInfo == nil {
// add
change := Change{
Path: info.path(),
Kind: ChangeAdd,
}
*changes = append(*changes, change)
info.added = true
}
// We make a copy so we can modify it to detect additions
// also, we only recurse on the old dir if the new info is a directory
// otherwise any previous delete/change is considered recursive
oldChildren := make(map[string]*FileInfo)
if oldInfo != nil && info.isDir() {
for k, v := range oldInfo.children {
oldChildren[k] = v
}
}
for name, newChild := range info.children {
oldChild, _ := oldChildren[name]
if oldChild != nil {
// change?
oldStat := oldChild.stat
newStat := newChild.stat
// Note: We can't compare inode or ctime or blocksize here, because these change
// when copying a file into a container. However, that is not generally a problem
// because any content change will change mtime, and any status change should
// be visible when actually comparing the stat fields. The only time this
// breaks down is if some code intentionally hides a change by setting
// back mtime
if statDifferent(oldStat, newStat) ||
bytes.Compare(oldChild.capability, newChild.capability) != 0 {
change := Change{
Path: newChild.path(),
Kind: ChangeModify,
}
*changes = append(*changes, change)
newChild.added = true
}
// Remove from copy so we can detect deletions
delete(oldChildren, name)
}
newChild.addChanges(oldChild, changes)
}
for _, oldChild := range oldChildren {
// delete
change := Change{
Path: oldChild.path(),
Kind: ChangeDelete,
}
*changes = append(*changes, change)
}
// If there were changes inside this directory, we need to add it, even if the directory
// itself wasn't changed. This is needed to properly save and restore filesystem permissions.
if len(*changes) > sizeAtEntry && info.isDir() && !info.added && info.path() != "/" {
change := Change{
Path: info.path(),
Kind: ChangeModify,
}
// Let's insert the directory entry before the recently added entries located inside this dir
*changes = append(*changes, change) // just to resize the slice, will be overwritten
copy((*changes)[sizeAtEntry+1:], (*changes)[sizeAtEntry:])
(*changes)[sizeAtEntry] = change
}
}
func (info *FileInfo) Changes(oldInfo *FileInfo) []Change {
var changes []Change
info.addChanges(oldInfo, &changes)
return changes
}
func newRootFileInfo() *FileInfo {
root := &FileInfo{
name: "/",
children: make(map[string]*FileInfo),
}
return root
}
// ChangesDirs compares two directories and generates an array of Change objects describing the changes.
// If oldDir is "", then all files in newDir will be Add-Changes.
func ChangesDirs(newDir, oldDir string) ([]Change, error) {
var (
oldRoot, newRoot *FileInfo
)
if oldDir == "" {
emptyDir, err := ioutil.TempDir("", "empty")
if err != nil {
return nil, err
}
defer os.Remove(emptyDir)
oldDir = emptyDir
}
oldRoot, newRoot, err := collectFileInfoForChanges(oldDir, newDir)
if err != nil {
return nil, err
}
return newRoot.Changes(oldRoot), nil
}
// ChangesSize calculates the size in bytes of the provided changes, based on newDir.
func ChangesSize(newDir string, changes []Change) int64 {
var size int64
for _, change := range changes {
if change.Kind == ChangeModify || change.Kind == ChangeAdd {
file := filepath.Join(newDir, change.Path)
fileInfo, _ := os.Lstat(file)
if fileInfo != nil && !fileInfo.IsDir() {
size += fileInfo.Size()
}
}
}
return size
}
// ExportChanges produces an Archive from the provided changes, relative to dir.
func ExportChanges(dir string, changes []Change) (Archive, error) {
reader, writer := io.Pipe()
go func() {
ta := &tarAppender{
TarWriter: tar.NewWriter(writer),
Buffer: pools.BufioWriter32KPool.Get(nil),
SeenFiles: make(map[uint64]string),
}
// this buffer is needed for the duration of this piped stream
defer pools.BufioWriter32KPool.Put(ta.Buffer)
sort.Sort(changesByPath(changes))
// In general we log errors here but ignore them because
// during e.g. a diff operation the container can continue
// mutating the filesystem and we can see transient errors
// from this
for _, change := range changes {
if change.Kind == ChangeDelete {
whiteOutDir := filepath.Dir(change.Path)
whiteOutBase := filepath.Base(change.Path)
whiteOut := filepath.Join(whiteOutDir, ".wh."+whiteOutBase)
timestamp := time.Now()
hdr := &tar.Header{
Name: whiteOut[1:],
Size: 0,
ModTime: timestamp,
AccessTime: timestamp,
ChangeTime: timestamp,
}
if err := ta.TarWriter.WriteHeader(hdr); err != nil {
logrus.Debugf("Can't write whiteout header: %s", err)
}
} else {
path := filepath.Join(dir, change.Path)
if err := ta.addTarFile(path, change.Path[1:]); err != nil {
logrus.Debugf("Can't add file %s to tar: %s", path, err)
}
}
}
// Make sure to check the error on Close.
if err := ta.TarWriter.Close(); err != nil {
logrus.Debugf("Can't close layer: %s", err)
}
if err := writer.Close(); err != nil {
logrus.Debugf("failed close Changes writer: %s", err)
}
}()
return reader, nil
}