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authorNalin Dahyabhai <nalin@redhat.com>2019-04-22 16:44:58 -0400
committerNalin Dahyabhai <nalin@redhat.com>2019-04-25 08:57:58 -0400
commit4daac4736e3476211de7c1672bb5161191666a91 (patch)
treeeff5bfa4d9b82363b07c09c96f44d11adcdd05a4 /libpod/image/image.go
parent5c81a117f16fde190acef331f5b88022fe11c550 (diff)
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image: rework parent/child/history matching
Rework our expectations of how images that are derived from each other look, so that we don't assume that an image that's derived from a base image always adds layers relative to that base image. Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
Diffstat (limited to 'libpod/image/image.go')
-rw-r--r--libpod/image/image.go229
1 files changed, 196 insertions, 33 deletions
diff --git a/libpod/image/image.go b/libpod/image/image.go
index 588809bbc..0b0002d42 100644
--- a/libpod/image/image.go
+++ b/libpod/image/image.go
@@ -679,7 +679,8 @@ type History struct {
Comment string `json:"comment"`
}
-// History gets the history of an image and information about its layers
+// History gets the history of an image and the IDs of images that are part of
+// its history
func (i *Image) History(ctx context.Context) ([]*History, error) {
img, err := i.toImageRef(ctx)
if err != nil {
@@ -690,31 +691,92 @@ func (i *Image) History(ctx context.Context) ([]*History, error) {
return nil, err
}
- // Get the IDs of the images making up the history layers
- // if the images exist locally in the store
+ // Use our layers list to find images that use one of them as its
+ // topmost layer.
+ interestingLayers := make(map[string]bool)
+ layer, err := i.imageruntime.store.Layer(i.TopLayer())
+ if err != nil {
+ return nil, err
+ }
+ for layer != nil {
+ interestingLayers[layer.ID] = true
+ if layer.Parent == "" {
+ break
+ }
+ layer, err = i.imageruntime.store.Layer(layer.Parent)
+ if err != nil {
+ return nil, err
+ }
+ }
+
+ // Get the IDs of the images that share some of our layers. Hopefully
+ // this step means that we'll be able to avoid reading the
+ // configuration of every single image in local storage later on.
images, err := i.imageruntime.GetImages()
if err != nil {
return nil, errors.Wrapf(err, "error getting images from store")
}
- imageIDs := []string{i.ID()}
- if err := i.historyLayerIDs(i.TopLayer(), images, &imageIDs); err != nil {
- return nil, errors.Wrap(err, "error getting image IDs for layers in history")
+ interestingImages := make([]*Image, 0, len(images))
+ for i := range images {
+ if interestingLayers[images[i].TopLayer()] {
+ interestingImages = append(interestingImages, images[i])
+ }
+ }
+
+ // Build a list of image IDs that correspond to our history entries.
+ historyImages := make([]*Image, len(oci.History))
+ if len(oci.History) > 0 {
+ // The starting image shares its whole history with itself.
+ historyImages[len(historyImages)-1] = i
+ for i := range interestingImages {
+ image, err := images[i].ociv1Image(ctx)
+ if err != nil {
+ return nil, errors.Wrapf(err, "error getting image configuration for image %q", images[i].ID())
+ }
+ // If the candidate has a longer history or no history
+ // at all, then it doesn't share the portion of our
+ // history that we're interested in matching with other
+ // images.
+ if len(image.History) == 0 || len(image.History) > len(historyImages) {
+ continue
+ }
+ // If we don't include all of the layers that the
+ // candidate image does (i.e., our rootfs didn't look
+ // like its rootfs at any point), then it can't be part
+ // of our history.
+ if len(image.RootFS.DiffIDs) > len(oci.RootFS.DiffIDs) {
+ continue
+ }
+ candidateLayersAreUsed := true
+ for i := range image.RootFS.DiffIDs {
+ if image.RootFS.DiffIDs[i] != oci.RootFS.DiffIDs[i] {
+ candidateLayersAreUsed = false
+ break
+ }
+ }
+ if !candidateLayersAreUsed {
+ continue
+ }
+ // If the candidate's entire history is an initial
+ // portion of our history, then we're based on it,
+ // either directly or indirectly.
+ sharedHistory := historiesMatch(oci.History, image.History)
+ if sharedHistory == len(image.History) {
+ historyImages[sharedHistory-1] = images[i]
+ }
+ }
}
var (
- imageID string
- imgIDCount = 0
size int64
sizeCount = 1
allHistory []*History
)
for i := len(oci.History) - 1; i >= 0; i-- {
- if imgIDCount < len(imageIDs) {
- imageID = imageIDs[imgIDCount]
- imgIDCount++
- } else {
- imageID = "<missing>"
+ imageID := "<missing>"
+ if historyImages[i] != nil {
+ imageID = historyImages[i].ID()
}
if !oci.History[i].EmptyLayer {
size = img.LayerInfos()[len(img.LayerInfos())-sizeCount].Size
@@ -1007,25 +1069,109 @@ func splitString(input string) string {
// the parent of any other layer in store. Double check that image with that
// layer exists as well.
func (i *Image) IsParent(ctx context.Context) (bool, error) {
- children, err := i.GetChildren(ctx)
+ children, err := i.getChildren(ctx, 1)
if err != nil {
return false, err
}
return len(children) > 0, nil
}
+// historiesMatch returns the number of entries in the histories which have the
+// same contents
+func historiesMatch(a, b []imgspecv1.History) int {
+ i := 0
+ for i < len(a) && i < len(b) {
+ if a[i].Created != nil && b[i].Created == nil {
+ return i
+ }
+ if a[i].Created == nil && b[i].Created != nil {
+ return i
+ }
+ if a[i].Created != nil && b[i].Created != nil {
+ if !a[i].Created.Equal(*(b[i].Created)) {
+ return i
+ }
+ }
+ if a[i].CreatedBy != b[i].CreatedBy {
+ return i
+ }
+ if a[i].Author != b[i].Author {
+ return i
+ }
+ if a[i].Comment != b[i].Comment {
+ return i
+ }
+ if a[i].EmptyLayer != b[i].EmptyLayer {
+ return i
+ }
+ i++
+ }
+ return i
+}
+
+// areParentAndChild checks diff ID and history in the two images and return
+// true if the second should be considered to be directly based on the first
+func areParentAndChild(parent, child *imgspecv1.Image) bool {
+ // the child and candidate parent should share all of the
+ // candidate parent's diff IDs, which together would have
+ // controlled which layers were used
+ if len(parent.RootFS.DiffIDs) > len(child.RootFS.DiffIDs) {
+ return false
+ }
+ childUsesCandidateDiffs := true
+ for i := range parent.RootFS.DiffIDs {
+ if child.RootFS.DiffIDs[i] != parent.RootFS.DiffIDs[i] {
+ childUsesCandidateDiffs = false
+ break
+ }
+ }
+ if !childUsesCandidateDiffs {
+ return false
+ }
+ // the child should have the same history as the parent, plus
+ // one more entry
+ if len(parent.History)+1 != len(child.History) {
+ return false
+ }
+ if historiesMatch(parent.History, child.History) != len(parent.History) {
+ return false
+ }
+ return true
+}
+
// GetParent returns the image ID of the parent. Return nil if a parent is not found.
func (i *Image) GetParent(ctx context.Context) (*Image, error) {
images, err := i.imageruntime.GetImages()
if err != nil {
return nil, err
}
- layer, err := i.imageruntime.store.Layer(i.TopLayer())
+ childLayer, err := i.imageruntime.store.Layer(i.TopLayer())
+ if err != nil {
+ return nil, err
+ }
+ // fetch the configuration for the child image
+ child, err := i.ociv1Image(ctx)
if err != nil {
return nil, err
}
for _, img := range images {
- if img.TopLayer() == layer.Parent {
+ if img.ID() == i.ID() {
+ continue
+ }
+ candidateLayer := img.TopLayer()
+ // as a child, our top layer is either the candidate parent's
+ // layer, or one that's derived from it, so skip over any
+ // candidate image where we know that isn't the case
+ if candidateLayer != childLayer.Parent && candidateLayer != childLayer.ID {
+ continue
+ }
+ // fetch the configuration for the candidate image
+ candidate, err := img.ociv1Image(ctx)
+ if err != nil {
+ return nil, err
+ }
+ // compare them
+ if areParentAndChild(candidate, child) {
return img, nil
}
}
@@ -1034,35 +1180,52 @@ func (i *Image) GetParent(ctx context.Context) (*Image, error) {
// GetChildren returns a list of the imageIDs that depend on the image
func (i *Image) GetChildren(ctx context.Context) ([]string, error) {
+ return i.getChildren(ctx, 0)
+}
+
+// getChildren returns a list of at most "max" imageIDs that depend on the image
+func (i *Image) getChildren(ctx context.Context, max int) ([]string, error) {
var children []string
images, err := i.imageruntime.GetImages()
if err != nil {
return nil, err
}
- layers, err := i.imageruntime.store.Layers()
+
+ // fetch the configuration for the parent image
+ parent, err := i.ociv1Image(ctx)
if err != nil {
return nil, err
}
+ parentLayer := i.TopLayer()
- for _, layer := range layers {
- if layer.Parent == i.TopLayer() {
- if imageID := getImageOfTopLayer(images, layer.ID); len(imageID) > 0 {
- children = append(children, imageID...)
- }
- }
- }
- return children, nil
-}
-
-// getImageOfTopLayer returns the image ID where layer is the top layer of the image
-func getImageOfTopLayer(images []*Image, layer string) []string {
- var matches []string
for _, img := range images {
- if img.TopLayer() == layer {
- matches = append(matches, img.ID())
+ if img.ID() == i.ID() {
+ continue
+ }
+ candidateLayer, err := img.Layer()
+ if err != nil {
+ return nil, err
+ }
+ // if this image's top layer is not our top layer, and is not
+ // based on our top layer, we can skip it
+ if candidateLayer.Parent != parentLayer && candidateLayer.ID != parentLayer {
+ continue
+ }
+ // fetch the configuration for the candidate image
+ candidate, err := img.ociv1Image(ctx)
+ if err != nil {
+ return nil, err
+ }
+ // compare them
+ if areParentAndChild(parent, candidate) {
+ children = append(children, img.ID())
+ }
+ // if we're not building an exhaustive list, maybe we're done?
+ if max > 0 && len(children) >= max {
+ break
}
}
- return matches
+ return children, nil
}
// InputIsID returns a bool if the user input for an image