Extract the daemon image cache to its own package

ImageCache is now independent of `Daemon` and is located in
`image/cache` package.

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

daemon/cache.go

@@ -1,254 +1,27 @@
 package daemon
 
 import (
-	"encoding/json"
-	"fmt"
-	"reflect"
-	"strings"
-
 	"github.com/Sirupsen/logrus"
-	containertypes "github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/builder"
-	"github.com/docker/docker/dockerversion"
-	"github.com/docker/docker/image"
-	"github.com/docker/docker/layer"
-	"github.com/docker/docker/runconfig"
-	"github.com/pkg/errors"
+	"github.com/docker/docker/image/cache"
 )
 
-// getLocalCachedImage returns the most recent created image that is a child
-// of the image with imgID, that had the same config when it was
-// created. nil is returned if a child cannot be found. An error is
-// returned if the parent image cannot be found.
-func (daemon *Daemon) getLocalCachedImage(imgID image.ID, config *containertypes.Config) (*image.Image, error) {
-	// Loop on the children of the given image and check the config
-	getMatch := func(siblings []image.ID) (*image.Image, error) {
-		var match *image.Image
-		for _, id := range siblings {
-			img, err := daemon.imageStore.Get(id)
-			if err != nil {
-				return nil, fmt.Errorf("unable to find image %q", id)
-			}
-
-			if runconfig.Compare(&img.ContainerConfig, config) {
-				// check for the most up to date match
-				if match == nil || match.Created.Before(img.Created) {
-					match = img
-				}
-			}
-		}
-		return match, nil
-	}
-
-	// In this case, this is `FROM scratch`, which isn't an actual image.
-	if imgID == "" {
-		images := daemon.imageStore.Map()
-		var siblings []image.ID
-		for id, img := range images {
-			if img.Parent == imgID {
-				siblings = append(siblings, id)
-			}
-		}
-		return getMatch(siblings)
-	}
-
-	// find match from child images
-	siblings := daemon.imageStore.Children(imgID)
-	return getMatch(siblings)
-}
-
 // MakeImageCache creates a stateful image cache.
 func (daemon *Daemon) MakeImageCache(sourceRefs []string) builder.ImageCache {
 	if len(sourceRefs) == 0 {
-		return &localImageCache{daemon}
+		return cache.NewLocal(daemon.imageStore)
 	}
 
-	cache := &imageCache{daemon: daemon, localImageCache: &localImageCache{daemon}}
+	cache := cache.New(daemon.imageStore)
 
 	for _, ref := range sourceRefs {
 		img, err := daemon.GetImage(ref)
 		if err != nil {
 			logrus.Warnf("Could not look up %s for cache resolution, skipping: %+v", ref, err)
 			continue
 		}
-		cache.sources = append(cache.sources, img)
+		cache.Populate(img)
 	}
 
 	return cache
 }
-
-// localImageCache is cache based on parent chain.
-type localImageCache struct {
-	daemon *Daemon
-}
-
-func (lic *localImageCache) GetCache(imgID string, config *containertypes.Config) (string, error) {
-	return getImageIDAndError(lic.daemon.getLocalCachedImage(image.ID(imgID), config))
-}
-
-// imageCache is cache based on history objects. Requires initial set of images.
-type imageCache struct {
-	sources         []*image.Image
-	daemon          *Daemon
-	localImageCache *localImageCache
-}
-
-func (ic *imageCache) restoreCachedImage(parent, target *image.Image, cfg *containertypes.Config) (image.ID, error) {
-	var history []image.History
-	rootFS := image.NewRootFS()
-	lenHistory := 0
-	if parent != nil {
-		history = parent.History
-		rootFS = parent.RootFS
-		lenHistory = len(parent.History)
-	}
-	history = append(history, target.History[lenHistory])
-	if layer := getLayerForHistoryIndex(target, lenHistory); layer != "" {
-		rootFS.Append(layer)
-	}
-
-	config, err := json.Marshal(&image.Image{
-		V1Image: image.V1Image{
-			DockerVersion: dockerversion.Version,
-			Config:        cfg,
-			Architecture:  target.Architecture,
-			OS:            target.OS,
-			Author:        target.Author,
-			Created:       history[len(history)-1].Created,
-		},
-		RootFS:     rootFS,
-		History:    history,
-		OSFeatures: target.OSFeatures,
-		OSVersion:  target.OSVersion,
-	})
-	if err != nil {
-		return "", errors.Wrap(err, "failed to marshal image config")
-	}
-
-	imgID, err := ic.daemon.imageStore.Create(config)
-	if err != nil {
-		return "", errors.Wrap(err, "failed to create cache image")
-	}
-
-	if parent != nil {
-		if err := ic.daemon.imageStore.SetParent(imgID, parent.ID()); err != nil {
-			return "", errors.Wrapf(err, "failed to set parent for %v to %v", target.ID(), parent.ID())
-		}
-	}
-	return imgID, nil
-}
-
-func (ic *imageCache) isParent(imgID, parentID image.ID) bool {
-	nextParent, err := ic.daemon.imageStore.GetParent(imgID)
-	if err != nil {
-		return false
-	}
-	if nextParent == parentID {
-		return true
-	}
-	return ic.isParent(nextParent, parentID)
-}
-
-func (ic *imageCache) GetCache(parentID string, cfg *containertypes.Config) (string, error) {
-	imgID, err := ic.localImageCache.GetCache(parentID, cfg)
-	if err != nil {
-		return "", err
-	}
-	if imgID != "" {
-		for _, s := range ic.sources {
-			if ic.isParent(s.ID(), image.ID(imgID)) {
-				return imgID, nil
-			}
-		}
-	}
-
-	var parent *image.Image
-	lenHistory := 0
-	if parentID != "" {
-		parent, err = ic.daemon.imageStore.Get(image.ID(parentID))
-		if err != nil {
-			return "", errors.Wrapf(err, "unable to find image %v", parentID)
-		}
-		lenHistory = len(parent.History)
-	}
-
-	for _, target := range ic.sources {
-		if !isValidParent(target, parent) || !isValidConfig(cfg, target.History[lenHistory]) {
-			continue
-		}
-
-		if len(target.History)-1 == lenHistory { // last
-			if parent != nil {
-				if err := ic.daemon.imageStore.SetParent(target.ID(), parent.ID()); err != nil {
-					return "", errors.Wrapf(err, "failed to set parent for %v to %v", target.ID(), parent.ID())
-				}
-			}
-			return target.ID().String(), nil
-		}
-
-		imgID, err := ic.restoreCachedImage(parent, target, cfg)
-		if err != nil {
-			return "", errors.Wrapf(err, "failed to restore cached image from %q to %v", parentID, target.ID())
-		}
-
-		ic.sources = []*image.Image{target} // avoid jumping to different target, tuned for safety atm
-		return imgID.String(), nil
-	}
-
-	return "", nil
-}
-
-func getImageIDAndError(img *image.Image, err error) (string, error) {
-	if img == nil || err != nil {
-		return "", err
-	}
-	return img.ID().String(), nil
-}
-
-func isValidParent(img, parent *image.Image) bool {
-	if len(img.History) == 0 {
-		return false
-	}
-	if parent == nil || len(parent.History) == 0 && len(parent.RootFS.DiffIDs) == 0 {
-		return true
-	}
-	if len(parent.History) >= len(img.History) {
-		return false
-	}
-	if len(parent.RootFS.DiffIDs) >= len(img.RootFS.DiffIDs) {
-		return false
-	}
-
-	for i, h := range parent.History {
-		if !reflect.DeepEqual(h, img.History[i]) {
-			return false
-		}
-	}
-	for i, d := range parent.RootFS.DiffIDs {
-		if d != img.RootFS.DiffIDs[i] {
-			return false
-		}
-	}
-	return true
-}
-
-func getLayerForHistoryIndex(image *image.Image, index int) layer.DiffID {
-	layerIndex := 0
-	for i, h := range image.History {
-		if i == index {
-			if h.EmptyLayer {
-				return ""
-			}
-			break
-		}
-		if !h.EmptyLayer {
-			layerIndex++
-		}
-	}
-	return image.RootFS.DiffIDs[layerIndex] // validate?
-}
-
-func isValidConfig(cfg *containertypes.Config, h image.History) bool {
-	// todo: make this format better than join that loses data
-	return strings.Join(cfg.Cmd, " ") == h.CreatedBy
-}