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image list: speed up
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Listing images has shown increasing performance penalties with an
increasing number of images.  Unless `--all` is specified, Podman
will filter intermediate images.  Determining intermediate images
has been done by finding (and comparing!) parent images which is
expensive.  We had to query the storage many times which turned it
into a bottleneck.

Instead, create a layer tree and assign one or more images to nodes that
match the images' top layer.  Determining the children of an image is
now exponentially faster as we already know the child images from the
layer graph and the images using the same top layer, which may also be
considered child images based on their history.

On my system with 510 images, a rootful image list drops from 6 secs
down to 0.3 secs.

Also use the tree to compute parent nodes, and to filter intermediate
images for pruning.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
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@vrothberg
vrothberg committed Aug 7, 2020
1 parent 1ed1e58 commit 8827100
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Showing 6 changed files with 276 additions and 147 deletions.
20 changes: 20 additions & 0 deletions libpod/image/filters.go
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,26 @@ func CreatedBeforeFilter(createTime time.Time) ResultFilter {
}
}

// IntermediateFilter returns filter for intermediate images (i.e., images
// with children and no tags).
func (ir *Runtime) IntermediateFilter(ctx context.Context, images []*Image) (ResultFilter, error) {
tree, err := ir.layerTree()
if err != nil {
return nil, err
}
return func(i *Image) bool {
if len(i.Names()) > 0 {
return true
}
children, err := tree.children(ctx, i, false)
if err != nil {
logrus.Error(err.Error())
return false
}
return len(children) == 0
}, nil
}

// CreatedAfterFilter allows you to filter on images created after
// the given time.Time
func CreatedAfterFilter(createTime time.Time) ResultFilter {
Expand Down
133 changes: 10 additions & 123 deletions libpod/image/image.go
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Original file line number Diff line number Diff line change
Expand Up @@ -856,26 +856,6 @@ func (i *Image) Dangling() bool {
return len(i.Names()) == 0
}

// Intermediate returns true if the image is cache or intermediate image.
// Cache image has parent and child.
func (i *Image) Intermediate(ctx context.Context) (bool, error) {
parent, err := i.IsParent(ctx)
if err != nil {
return false, err
}
if !parent {
return false, nil
}
img, err := i.GetParent(ctx)
if err != nil {
return false, err
}
if img != nil {
return true, nil
}
return false, nil
}

// User returns the image's user
func (i *Image) User(ctx context.Context) (string, error) {
imgInspect, err := i.inspect(ctx, false)
Expand Down Expand Up @@ -1214,7 +1194,7 @@ 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, 1)
children, err := i.getChildren(ctx, false)
if err != nil {
if errors.Cause(err) == ErrImageIsBareList {
return false, nil
Expand Down Expand Up @@ -1289,63 +1269,16 @@ func areParentAndChild(parent, child *imgspecv1.Image) bool {

// 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) {
var childLayer *storage.Layer
images, err := i.imageruntime.GetImages()
tree, err := i.imageruntime.layerTree()
if err != nil {
return nil, err
}
if i.TopLayer() != "" {
if childLayer, err = i.imageruntime.store.Layer(i.TopLayer()); err != nil {
return nil, err
}
}
// fetch the configuration for the child image
child, err := i.ociv1Image(ctx)
if err != nil {
if errors.Cause(err) == ErrImageIsBareList {
return nil, nil
}
return nil, err
}
for _, img := range images {
if img.ID() == i.ID() {
continue
}
candidateLayer := img.TopLayer()
// as a child, our top layer, if we have one, 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 childLayer != nil {
// The child has at least one layer, so a parent would
// have a top layer that's either the same as the child's
// top layer or the top layer's recorded parent layer,
// which could be an empty value.
if candidateLayer != childLayer.Parent && candidateLayer != childLayer.ID {
continue
}
} else {
// The child has no layers, but the candidate does.
if candidateLayer != "" {
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
}
}
return nil, nil
return tree.parent(ctx, i)
}

// GetChildren returns a list of the imageIDs that depend on the image
func (i *Image) GetChildren(ctx context.Context) ([]string, error) {
children, err := i.getChildren(ctx, 0)
children, err := i.getChildren(ctx, true)
if err != nil {
if errors.Cause(err) == ErrImageIsBareList {
return nil, nil
Expand All @@ -1355,62 +1288,15 @@ func (i *Image) GetChildren(ctx context.Context) ([]string, error) {
return children, nil
}

// 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

if _, err := i.toImageRef(ctx); err != nil {
return nil, nil
}

images, err := i.imageruntime.GetImages()
if err != nil {
return nil, err
}

// fetch the configuration for the parent image
parent, err := i.ociv1Image(ctx)
// getChildren returns a list of imageIDs that depend on the image. If all is
// false, only the first child image is returned.
func (i *Image) getChildren(ctx context.Context, all bool) ([]string, error) {
tree, err := i.imageruntime.layerTree()
if err != nil {
return nil, err
}
parentLayer := i.TopLayer()

for _, img := range images {
if img.ID() == i.ID() {
continue
}
if img.TopLayer() == "" {
if parentLayer != "" {
// this image has no layers, but we do, so
// it can't be derived from this one
continue
}
} else {
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 children, nil
return tree.children(ctx, i, all)
}

// InputIsID returns a bool if the user input for an image
Expand Down Expand Up @@ -1667,6 +1553,7 @@ type LayerInfo struct {

// GetLayersMapWithImageInfo returns map of image-layers, with associated information like RepoTags, parent and list of child layers.
func GetLayersMapWithImageInfo(imageruntime *Runtime) (map[string]*LayerInfo, error) {
// TODO: evaluate if we can reuse `layerTree` here.

// Memory allocated to store map of layers with key LayerID.
// Map will build dependency chain with ParentID and ChildID(s)
Expand Down
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