c8d: add support for docker diff

Signed-off-by: Laura Brehm <laurabrehm@hey.com>

api/server/router/container/backend.go

@@ -48,7 +48,7 @@ type stateBackend interface {
 
 // monitorBackend includes functions to implement to provide containers monitoring functionality.
 type monitorBackend interface {
-	ContainerChanges(name string) ([]archive.Change, error)
+	ContainerChanges(ctx context.Context, name string) ([]archive.Change, error)
 	ContainerInspect(ctx context.Context, name string, size bool, version string) (interface{}, error)
 	ContainerLogs(ctx context.Context, name string, config *types.ContainerLogsOptions) (msgs <-chan *backend.LogMessage, tty bool, err error)
 	ContainerStats(ctx context.Context, name string, config *backend.ContainerStatsConfig) error

api/server/router/container/container_routes.go

@@ -401,7 +401,7 @@ func (s *containerRouter) postContainersWait(ctx context.Context, w http.Respons
 }
 
 func (s *containerRouter) getContainersChanges(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
-	changes, err := s.backend.ContainerChanges(vars["name"])
+	changes, err := s.backend.ContainerChanges(ctx, vars["name"])
 	if err != nil {
 		return err
 	}

daemon/changes.go

@@ -1,16 +1,17 @@
 package daemon // import "github.com/docker/docker/daemon"
 
 import (
+	"context"
 	"errors"
 	"time"
 
-	"github.com/docker/docker/errdefs"
 	"github.com/docker/docker/pkg/archive"
 )
 
 // ContainerChanges returns a list of container fs changes
-func (daemon *Daemon) ContainerChanges(name string) ([]archive.Change, error) {
+func (daemon *Daemon) ContainerChanges(ctx context.Context, name string) ([]archive.Change, error) {
 	start := time.Now()
+
 	container, err := daemon.GetContainer(name)
 	if err != nil {
 		return nil, err
@@ -20,15 +21,7 @@ func (daemon *Daemon) ContainerChanges(name string) ([]archive.Change, error) {
 		return nil, errors.New("Windows does not support diff of a running container")
 	}
 
-	if daemon.UsesSnapshotter() {
-		return nil, errdefs.NotImplemented(errors.New("not implemented"))
-	}
-	container.Lock()
-	defer container.Unlock()
-	if container.RWLayer == nil {
-		return nil, errors.New("RWLayer of container " + name + " is unexpectedly nil")
-	}
-	c, err := container.RWLayer.Changes()
+	c, err := daemon.imageService.Changes(ctx, container)
 	if err != nil {
 		return nil, err
 	}

daemon/containerd/image_changes.go

@@ -0,0 +1,69 @@
+package containerd
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/mount"
+	"github.com/docker/docker/container"
+	"github.com/docker/docker/pkg/archive"
+	"github.com/google/uuid"
+	"github.com/opencontainers/image-spec/identity"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/sirupsen/logrus"
+)
+
+func (i *ImageService) Changes(ctx context.Context, container *container.Container) ([]archive.Change, error) {
+	cs := i.client.ContentStore()
+
+	imageManifestBytes, err := content.ReadBlob(ctx, cs, *container.ImageManifest)
+	if err != nil {
+		return nil, err
+	}
+	var manifest ocispec.Manifest
+	if err := json.Unmarshal(imageManifestBytes, &manifest); err != nil {
+		return nil, err
+	}
+
+	imageConfigBytes, err := content.ReadBlob(ctx, cs, manifest.Config)
+	if err != nil {
+		return nil, err
+	}
+	var image ocispec.Image
+	if err := json.Unmarshal(imageConfigBytes, &image); err != nil {
+		return nil, err
+	}
+
+	rnd, err := uuid.NewRandom()
+	if err != nil {
+		return nil, err
+	}
+
+	snapshotter := i.client.SnapshotService(i.snapshotter)
+
+	diffIDs := image.RootFS.DiffIDs
+	parent, err := snapshotter.View(ctx, rnd.String(), identity.ChainID(diffIDs).String())
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if err := snapshotter.Remove(ctx, rnd.String()); err != nil {
+			logrus.WithError(err).WithField("key", rnd.String()).Warn("remove temporary snapshot")
+		}
+	}()
+
+	mounts, err := snapshotter.Mounts(ctx, container.ID)
+	if err != nil {
+		return nil, err
+	}
+
+	var changes []archive.Change
+	err = mount.WithReadonlyTempMount(ctx, mounts, func(fs string) error {
+		return mount.WithTempMount(ctx, parent, func(root string) error {
+			changes, err = archive.ChangesDirs(fs, root)
+			return err
+		})
+	})
+	return changes, err
+}

daemon/image_service.go

@@ -16,6 +16,7 @@ import (
 	"github.com/docker/docker/daemon/images"
 	"github.com/docker/docker/image"
 	"github.com/docker/docker/layer"
+	"github.com/docker/docker/pkg/archive"
 	v1 "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
@@ -60,6 +61,7 @@ type ImageService interface {
 	GetContainerLayerSize(ctx context.Context, containerID string) (int64, int64, error)
 	Mount(ctx context.Context, container *container.Container) error
 	Unmount(ctx context.Context, container *container.Container) error
+	Changes(ctx context.Context, container *container.Container) ([]archive.Change, error)
 
 	// Windows specific
 

daemon/images/image_changes.go

@@ -0,0 +1,19 @@
+package images
+
+import (
+	"context"
+	"errors"
+
+	"github.com/docker/docker/container"
+	"github.com/docker/docker/pkg/archive"
+)
+
+func (i *ImageService) Changes(ctx context.Context, container *container.Container) ([]archive.Change, error) {
+	container.Lock()
+	defer container.Unlock()
+
+	if container.RWLayer == nil {
+		return nil, errors.New("RWLayer of container " + container.Name + " is unexpectedly nil")
+	}
+	return container.RWLayer.Changes()
+}