libimage: prune: allow for removing external containers

Support pruning images in use by external containers (e.g., build
containers).  Requires extending the containers filter, adding a
callback to libpod and a new options for image removal.

Tests will be added to Podman.

Signed-off-by: Valentin Rothberg <[email protected]>

libimage/filters.go

@@ -47,11 +47,11 @@ func filterImages(images []*Image, filters []filterFunc) ([]*Image, error) {
 // compileImageFilters creates `filterFunc`s for the specified filters.  The
 // required format is `key=value` with the following supported keys:
 //           after, since, before, containers, dangling, id, label, readonly, reference, intermediate
-func (r *Runtime) compileImageFilters(ctx context.Context, filters []string) ([]filterFunc, error) {
-	logrus.Tracef("Parsing image filters %s", filters)
+func (r *Runtime) compileImageFilters(ctx context.Context, options *ListImagesOptions) ([]filterFunc, error) {
+	logrus.Tracef("Parsing image filters %s", options.Filters)
 
 	filterFuncs := []filterFunc{}
-	for _, filter := range filters {
+	for _, filter := range options.Filters {
 		var key, value string
 		split := strings.SplitN(filter, "=", 2)
 		if len(split) != 2 {
@@ -77,11 +77,16 @@ func (r *Runtime) compileImageFilters(ctx context.Context, filters []string) ([]
 			filterFuncs = append(filterFuncs, filterBefore(img.Created()))
 
 		case "containers":
-			containers, err := strconv.ParseBool(value)
-			if err != nil {
-				return nil, errors.Wrapf(err, "non-boolean value %q for dangling filter", value)
+			switch value {
+			case "false", "true":
+			case "external":
+				if options.IsExternalContainerFunc == nil {
+					return nil, fmt.Errorf("libimage error: external containers filter without callback")
+				}
+			default:
+				return nil, fmt.Errorf("unsupported value %q for containers filter", value)
 			}
-			filterFuncs = append(filterFuncs, filterContainers(containers))
+			filterFuncs = append(filterFuncs, filterContainers(value, options.IsExternalContainerFunc))
 
 		case "dangling":
 			dangling, err := strconv.ParseBool(value)
@@ -190,13 +195,28 @@ func filterReadOnly(value bool) filterFunc {
 }
 
 // filterContainers creates a container filter for matching the specified value.
-func filterContainers(value bool) filterFunc {
+func filterContainers(value string, fn IsExternalContainerFunc) filterFunc {
 	return func(img *Image) (bool, error) {
 		ctrs, err := img.Containers()
 		if err != nil {
 			return false, err
 		}
-		return (len(ctrs) > 0) == value, nil
+		if value != "external" {
+			boolValue := value == "true"
+			return (len(ctrs) > 0) == boolValue, nil
+		}
+
+		// Check whether all associated containers are external ones.
+		for _, c := range ctrs {
+			isExternal, err := fn(c)
+			if err != nil {
+				return false, fmt.Errorf("checking if %s is an external container in filter: %w", c, err)
+			}
+			if !isExternal {
+				return isExternal, nil
+			}
+		}
+		return true, nil
 	}
 }
 

libimage/image.go

@@ -2,6 +2,7 @@ package libimage
 
 import (
 	"context"
+	"fmt"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -232,20 +233,38 @@ func (i *Image) Containers() ([]string, error) {
 }
 
 // removeContainers removes all containers using the image.
-func (i *Image) removeContainers(fn RemoveContainerFunc) error {
-	// Execute the custom removal func if specified.
-	if fn != nil {
-		logrus.Debugf("Removing containers of image %s with custom removal function", i.ID())
-		if err := fn(i.ID()); err != nil {
-			return err
-		}
+func (i *Image) removeContainers(options *RemoveImagesOptions) error {
+	if !options.Force && !options.ExternalContainers {
+		// Nothing to do.
+		return nil
 	}
 
 	containers, err := i.Containers()
 	if err != nil {
 		return err
 	}
 
+	if options.Force {
+		// Execute the custom removal func if specified.
+		if options.RemoveContainerFunc != nil {
+			logrus.Debugf("Removing containers of image %s with custom removal function", i.ID())
+			if err := options.RemoveContainerFunc(i.ID()); err != nil {
+				return err
+			}
+		}
+	} else if options.ExternalContainers {
+		// All containers must be external ones,.
+		for _, cID := range containers {
+			isExternal, err := options.IsExternalContainerFunc(cID)
+			if err != nil {
+				return fmt.Errorf("checking if %s is an external container: %w", cID, err)
+			}
+			if !isExternal {
+				return fmt.Errorf("cannot remove container %s: not an external container", cID)
+			}
+		}
+	}
+
 	logrus.Debugf("Removing containers of image %s from the local containers storage", i.ID())
 	var multiE error
 	for _, cID := range containers {
@@ -392,11 +411,9 @@ func (i *Image) removeRecursive(ctx context.Context, rmMap map[string]*RemoveIma
 		return processedIDs, nil
 	}
 
-	// Perform the actual removal. First, remove containers if needed.
-	if options.Force {
-		if err := i.removeContainers(options.RemoveContainerFunc); err != nil {
-			return processedIDs, err
-		}
+	// Perform the container removal, if needed.
+	if err := i.removeContainers(options); err != nil {
+		return processedIDs, err
 	}
 
 	// Podman/Docker compat: we only report an image as removed if it has

libimage/image_test.go

@@ -94,10 +94,13 @@ func TestImageFunctions(t *testing.T) {
 	require.Nil(t, containers)
 
 	// Since we have no containers here, we can only smoke test.
-	require.NoError(t, image.removeContainers(nil))
-	require.Error(t, image.removeContainers(func(_ string) error {
-		return errors.New("TEST")
-	}))
+	rmOptions := &RemoveImagesOptions{
+		RemoveContainerFunc: func(_ string) error {
+			return errors.New("TEST")
+		},
+		Force: true,
+	}
+	require.Error(t, image.removeContainers(rmOptions))
 
 	// Two items since both names are "Named".
 	namedRepoTags, err := image.NamedRepoTags()

libimage/runtime.go

@@ -2,6 +2,7 @@ package libimage
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"strings"
 
@@ -484,17 +485,28 @@ func (r *Runtime) imageReferenceMatchesContext(ref types.ImageReference, options
 	return true, nil
 }
 
+// IsExternalContainerFunc allows for checking whether the specified container
+// is an external one.  The definition of an external container can be set by
+// callers.
+type IsExternalContainerFunc func(containerID string) (bool, error)
+
 // ListImagesOptions allow for customizing listing images.
 type ListImagesOptions struct {
 	// Filters to filter the listed images.  Supported filters are
 	// * after,before,since=image
+	// * containers=true,false,external
 	// * dangling=true,false
 	// * intermediate=true,false (useful for pruning images)
 	// * id=id
 	// * label=key[=value]
 	// * readonly=true,false
 	// * reference=name[:tag] (wildcards allowed)
 	Filters []string
+	// IsExternalContainerFunc allows for checking whether the specified
+	// container is an external one (when containers=external filter is
+	// used).  The definition of an external container can be set by
+	// callers.
+	IsExternalContainerFunc IsExternalContainerFunc
 }
 
 // ListImages lists images in the local container storage.  If names are
@@ -525,7 +537,7 @@ func (r *Runtime) ListImages(ctx context.Context, names []string, options *ListI
 
 	var filters []filterFunc
 	if len(options.Filters) > 0 {
-		compiledFilters, err := r.compileImageFilters(ctx, options.Filters)
+		compiledFilters, err := r.compileImageFilters(ctx, options)
 		if err != nil {
 			return nil, err
 		}
@@ -550,8 +562,17 @@ type RemoveImagesOptions struct {
 	// containers using a specific image.  By default, all containers in
 	// the local containers storage will be removed (if Force is set).
 	RemoveContainerFunc RemoveContainerFunc
+	// IsExternalContainerFunc allows for checking whether the specified
+	// container is an external one (when containers=external filter is
+	// used).  The definition of an external container can be set by
+	// callers.
+	IsExternalContainerFunc IsExternalContainerFunc
+	// Remove external containers even when Force is false.  Requires
+	// IsExternalContainerFunc to be specified.
+	ExternalContainers bool
 	// Filters to filter the removed images.  Supported filters are
 	// * after,before,since=image
+	// * containers=true,false,external
 	// * dangling=true,false
 	// * intermediate=true,false (useful for pruning images)
 	// * id=id
@@ -581,6 +602,10 @@ func (r *Runtime) RemoveImages(ctx context.Context, names []string, options *Rem
 		options = &RemoveImagesOptions{}
 	}
 
+	if options.ExternalContainers && options.IsExternalContainerFunc == nil {
+		return nil, []error{fmt.Errorf("libimage error: cannot remove external containers without callback")}
+	}
+
 	// The logic here may require some explanation.  Image removal is
 	// surprisingly complex since it is recursive (intermediate parents are
 	// removed) and since multiple items in `names` may resolve to the
@@ -635,7 +660,11 @@ func (r *Runtime) RemoveImages(ctx context.Context, names []string, options *Rem
 		}
 
 	default:
-		filteredImages, err := r.ListImages(ctx, nil, &ListImagesOptions{Filters: options.Filters})
+		options := &ListImagesOptions{
+			IsExternalContainerFunc: options.IsExternalContainerFunc,
+			Filters:                 options.Filters,
+		}
+		filteredImages, err := r.ListImages(ctx, nil, options)
 		if err != nil {
 			appendError(err)
 			return nil, rmErrors