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moby--moby/daemon/graphdriver/fsdiff.go

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// +build daemon
package graphdriver
import (
"time"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/chrootarchive"
"github.com/docker/docker/pkg/ioutils"
)
// naiveDiffDriver takes a ProtoDriver and adds the
// capability of the Diffing methods which it may or may not
// support on its own. See the comment on the exported
// NaiveDiffDriver function below.
// Notably, the AUFS driver doesn't need to be wrapped like this.
type naiveDiffDriver struct {
ProtoDriver
}
// NaiveDiffDriver returns a fully functional driver that wraps the
// given ProtoDriver and adds the capability of the following methods which
// it may or may not support on its own:
// Diff(id, parent string) (archive.Archive, error)
// Changes(id, parent string) ([]archive.Change, error)
// ApplyDiff(id, parent string, diff archive.Reader) (size int64, err error)
// DiffSize(id, parent string) (size int64, err error)
func NaiveDiffDriver(driver ProtoDriver) Driver {
return &naiveDiffDriver{ProtoDriver: driver}
}
// Diff produces an archive of the changes between the specified
// layer and its parent layer which may be "".
func (gdw *naiveDiffDriver) Diff(id, parent string) (arch archive.Archive, err error) {
driver := gdw.ProtoDriver
layerFs, err := driver.Get(id, "")
if err != nil {
return nil, err
}
defer func() {
if err != nil {
driver.Put(id)
}
}()
if parent == "" {
archive, err := archive.Tar(layerFs, archive.Uncompressed)
if err != nil {
return nil, err
}
return ioutils.NewReadCloserWrapper(archive, func() error {
err := archive.Close()
driver.Put(id)
return err
}), nil
}
parentFs, err := driver.Get(parent, "")
if err != nil {
return nil, err
}
defer driver.Put(parent)
changes, err := archive.ChangesDirs(layerFs, parentFs)
if err != nil {
return nil, err
}
archive, err := archive.ExportChanges(layerFs, changes)
if err != nil {
return nil, err
}
return ioutils.NewReadCloserWrapper(archive, func() error {
err := archive.Close()
driver.Put(id)
return err
}), nil
}
// Changes produces a list of changes between the specified layer
// and its parent layer. If parent is "", then all changes will be ADD changes.
func (gdw *naiveDiffDriver) Changes(id, parent string) ([]archive.Change, error) {
driver := gdw.ProtoDriver
layerFs, err := driver.Get(id, "")
if err != nil {
return nil, err
}
defer driver.Put(id)
parentFs := ""
if parent != "" {
parentFs, err = driver.Get(parent, "")
if err != nil {
return nil, err
}
defer driver.Put(parent)
}
return archive.ChangesDirs(layerFs, parentFs)
}
// ApplyDiff extracts the changeset from the given diff into the
// layer with the specified id and parent, returning the size of the
// new layer in bytes.
func (gdw *naiveDiffDriver) ApplyDiff(id, parent string, diff archive.Reader) (size int64, err error) {
driver := gdw.ProtoDriver
// Mount the root filesystem so we can apply the diff/layer.
layerFs, err := driver.Get(id, "")
if err != nil {
return
}
defer driver.Put(id)
start := time.Now().UTC()
logrus.Debugf("Start untar layer")
if size, err = chrootarchive.ApplyUncompressedLayer(layerFs, diff); err != nil {
return
}
logrus.Debugf("Untar time: %vs", time.Now().UTC().Sub(start).Seconds())
return
}
// DiffSize calculates the changes between the specified layer
// and its parent and returns the size in bytes of the changes
// relative to its base filesystem directory.
func (gdw *naiveDiffDriver) DiffSize(id, parent string) (size int64, err error) {
driver := gdw.ProtoDriver
changes, err := gdw.Changes(id, parent)
if err != nil {
return
}
layerFs, err := driver.Get(id, "")
if err != nil {
return
}
defer driver.Put(id)
return archive.ChangesSize(layerFs, changes), nil
}