dotcloud/docker

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daemon/images/image_delete.go

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package images // import "github.com/docker/docker/daemon/images"

import (
    "context"
    "fmt"
    "strings"
    "time"

    "github.com/distribution/reference"
    "github.com/docker/docker/api/types/backend"
    "github.com/docker/docker/api/types/events"
    imagetypes "github.com/docker/docker/api/types/image"
    "github.com/docker/docker/container"
    "github.com/docker/docker/errdefs"
    "github.com/docker/docker/image"
    "github.com/docker/docker/pkg/stringid"
    "github.com/pkg/errors"
)

type conflictType int

const (
    conflictDependentChild conflictType = 1 << iota
    conflictRunningContainer
    conflictActiveReference
    conflictStoppedContainer
    conflictHard = conflictDependentChild | conflictRunningContainer
    conflictSoft = conflictActiveReference | conflictStoppedContainer
)

// ImageDelete deletes the image referenced by the given imageRef from this
// daemon. The given imageRef can be an image ID, ID prefix, or a repository
// reference (with an optional tag or digest, defaulting to the tag name
// "latest"). There is differing behavior depending on whether the given
// imageRef is a repository reference or not.
//
// If the given imageRef is a repository reference then that repository
// reference will be removed. However, if there exists any containers which
// were created using the same image reference then the repository reference
// cannot be removed unless either there are other repository references to the
// same image or force is true. Following removal of the repository reference,
// the referenced image itself will attempt to be deleted as described below
// but quietly, meaning any image delete conflicts will cause the image to not
// be deleted and the conflict will not be reported.
//
// There may be conflicts preventing deletion of an image and these conflicts
// are divided into two categories grouped by their severity:
//
// Hard Conflict:
//   - a pull or build using the image.
//   - any descendant image.
//   - any running container using the image.
//
// Soft Conflict:
//   - any stopped container using the image.
//   - any repository tag or digest references to the image.
//
// The image cannot be removed if there are any hard conflicts and can be
// removed if there are soft conflicts only if force is true.
//
// If prune is true, ancestor images will each attempt to be deleted quietly,
// meaning any delete conflicts will cause the image to not be deleted and the
// conflict will not be reported.
func (i *ImageService) ImageDelete(ctx context.Context, imageRef string, force, prune bool) ([]imagetypes.DeleteResponse, error) {
    start := time.Now()
    records := []imagetypes.DeleteResponse{}

    img, err := i.GetImage(ctx, imageRef, backend.GetImageOpts{})
    if err != nil {
        return nil, err
    }

    imgID := img.ID()
    repoRefs := i.referenceStore.References(imgID.Digest())

    using := func(c *container.Container) bool {
        return c.ImageID == imgID
    }

    var removedRepositoryRef bool
    if !isImageIDPrefix(imgID.String(), imageRef) {
        // A repository reference was given and should be removed
        // first. We can only remove this reference if either force is
        // true, there are multiple repository references to this
        // image, or there are no containers using the given reference.
        if !force && isSingleReference(repoRefs) {
            if ctr := i.containers.First(using); ctr != nil {
                // If we removed the repository reference then
                // this image would remain "dangling" and since
                // we really want to avoid that the client must
                // explicitly force its removal.
                err := errors.Errorf("conflict: unable to remove repository reference %q (must force) - container %s is using its referenced image %s", imageRef, stringid.TruncateID(ctr.ID), stringid.TruncateID(imgID.String()))
                return nil, errdefs.Conflict(err)
            }
        }

        parsedRef, err := reference.ParseNormalizedNamed(imageRef)
        if err != nil {
            return nil, err
        }

        parsedRef, err = i.removeImageRef(parsedRef)
        if err != nil {
            return nil, err
        }

        untaggedRecord := imagetypes.DeleteResponse{Untagged: reference.FamiliarString(parsedRef)}

        i.LogImageEvent(imgID.String(), imgID.String(), events.ActionUnTag)
        records = append(records, untaggedRecord)

        repoRefs = i.referenceStore.References(imgID.Digest())

        // If a tag reference was removed and the only remaining
        // references to the same repository are digest references,
        // then clean up those digest references.
        if _, isCanonical := parsedRef.(reference.Canonical); !isCanonical {
            foundRepoTagRef := false
            for _, repoRef := range repoRefs {
                if _, repoRefIsCanonical := repoRef.(reference.Canonical); !repoRefIsCanonical && parsedRef.Name() == repoRef.Name() {
                    foundRepoTagRef = true
                    break
                }
            }
            if !foundRepoTagRef {
                // Remove canonical references from same repository
                var remainingRefs []reference.Named
                for _, repoRef := range repoRefs {
                    if _, repoRefIsCanonical := repoRef.(reference.Canonical); repoRefIsCanonical && parsedRef.Name() == repoRef.Name() {
                        if _, err := i.removeImageRef(repoRef); err != nil {
                            return records, err
                        }
                        records = append(records, imagetypes.DeleteResponse{Untagged: reference.FamiliarString(repoRef)})
                    } else {
                        remainingRefs = append(remainingRefs, repoRef)
                    }
                }
                repoRefs = remainingRefs
            }
        }

        // If it has remaining references then the untag finished the remove
        if len(repoRefs) > 0 {
            return records, nil
        }

        removedRepositoryRef = true
    } else {
        // If an ID reference was given AND there is at most one tag
        // reference to the image AND all references are within one
        // repository, then remove all references.
        if isSingleReference(repoRefs) {
            c := conflictHard
            if !force {
                c |= conflictSoft &^ conflictActiveReference
            }
            if conflict := i.checkImageDeleteConflict(imgID, c); conflict != nil {
                return nil, conflict
            }

            for _, repoRef := range repoRefs {
                parsedRef, err := i.removeImageRef(repoRef)
                if err != nil {
                    return nil, err
                }
                i.LogImageEvent(imgID.String(), imgID.String(), events.ActionUnTag)
                records = append(records, imagetypes.DeleteResponse{Untagged: reference.FamiliarString(parsedRef)})
            }
        }
    }

    if err := i.imageDeleteHelper(imgID, &records, force, prune, removedRepositoryRef); err != nil {
        return nil, err
    }

    ImageActions.WithValues("delete").UpdateSince(start)

    return records, nil
}

// isSingleReference returns true when all references are from one repository
// and there is at most one tag. Returns false for empty input.
func isSingleReference(repoRefs []reference.Named) bool {
    if len(repoRefs) <= 1 {
        return len(repoRefs) == 1
    }
    var singleRef reference.Named
    canonicalRefs := map[string]struct{}{}
    for _, repoRef := range repoRefs {
        if _, isCanonical := repoRef.(reference.Canonical); isCanonical {
            canonicalRefs[repoRef.Name()] = struct{}{}
        } else if singleRef == nil {
            singleRef = repoRef
        } else {
            return false
        }
    }
    if singleRef == nil {
        // Just use first canonical ref
        singleRef = repoRefs[0]
    }
    _, ok := canonicalRefs[singleRef.Name()]
    return len(canonicalRefs) == 1 && ok
}

// isImageIDPrefix returns whether the given possiblePrefix is a prefix of the
// given imageID.
func isImageIDPrefix(imageID, possiblePrefix string) bool {
    if strings.HasPrefix(imageID, possiblePrefix) {
        return true
    }

    if i := strings.IndexRune(imageID, ':'); i >= 0 {
        return strings.HasPrefix(imageID[i+1:], possiblePrefix)
    }

    return false
}

// removeImageRef attempts to parse and remove the given image reference from
// this daemon's store of repository tag/digest references. The given
// repositoryRef must not be an image ID but a repository name followed by an
// optional tag or digest reference. If tag or digest is omitted, the default
// tag is used. Returns the resolved image reference and an error.
func (i *ImageService) removeImageRef(ref reference.Named) (reference.Named, error) {
    ref = reference.TagNameOnly(ref)

    // Ignore the boolean value returned, as far as we're concerned, this
    // is an idempotent operation and it's okay if the reference didn't
    // exist in the first place.
    _, err := i.referenceStore.Delete(ref)

    return ref, err
}

// removeAllReferencesToImageID attempts to remove every reference to the given
// imgID from this daemon's store of repository tag/digest references. Returns
// on the first encountered error. Removed references are logged to this
// daemon's event service. An "Untagged" types.ImageDeleteResponseItem is added to the
// given list of records.
func (i *ImageService) removeAllReferencesToImageID(imgID image.ID, records *[]imagetypes.DeleteResponse) error {
    for _, imageRef := range i.referenceStore.References(imgID.Digest()) {
        parsedRef, err := i.removeImageRef(imageRef)
        if err != nil {
            return err
        }
        i.LogImageEvent(imgID.String(), imgID.String(), events.ActionUnTag)
        *records = append(*records, imagetypes.DeleteResponse{
            Untagged: reference.FamiliarString(parsedRef),
        })
    }

    return nil
}

// ImageDeleteConflict holds a soft or hard conflict and an associated error.
// Implements the error interface.
type imageDeleteConflict struct {
    hard    bool
    used    bool
    imgID   image.ID
    message string
}

func (idc *imageDeleteConflict) Error() string {
    var forceMsg string
    if idc.hard {
        forceMsg = "cannot be forced"
    } else {
        forceMsg = "must be forced"
    }

    return fmt.Sprintf("conflict: unable to delete %s (%s) - %s", stringid.TruncateID(idc.imgID.String()), forceMsg, idc.message)
}

func (idc *imageDeleteConflict) Conflict() {}

// imageDeleteHelper attempts to delete the given image from this daemon. If
// the image has any hard delete conflicts (child images or running containers
// using the image) then it cannot be deleted. If the image has any soft delete
// conflicts (any tags/digests referencing the image or any stopped container
// using the image) then it can only be deleted if force is true. If the delete
// succeeds and prune is true, the parent images are also deleted if they do
// not have any soft or hard delete conflicts themselves. Any deleted images
// and untagged references are appended to the given records. If any error or
// conflict is encountered, it will be returned immediately without deleting
// the image. If quiet is true, any encountered conflicts will be ignored and
// the function will return nil immediately without deleting the image.
func (i *ImageService) imageDeleteHelper(imgID image.ID, records *[]imagetypes.DeleteResponse, force, prune, quiet bool) error {
    // First, determine if this image has any conflicts. Ignore soft conflicts
    // if force is true.
    c := conflictHard
    if !force {
        c |= conflictSoft
    }
    if conflict := i.checkImageDeleteConflict(imgID, c); conflict != nil {
        if quiet && (!i.imageIsDangling(imgID) || conflict.used) {
            // Ignore conflicts UNLESS the image is "dangling" or not being used in
            // which case we want the user to know.
            return nil
        }

        // There was a conflict and it's either a hard conflict OR we are not
        // forcing deletion on soft conflicts.
        return conflict
    }

    parent, err := i.imageStore.GetParent(imgID)
    if err != nil {
        // There may be no parent
        parent = ""
    }

    // Delete all repository tag/digest references to this image.
    if err := i.removeAllReferencesToImageID(imgID, records); err != nil {
        return err
    }

    removedLayers, err := i.imageStore.Delete(imgID)
    if err != nil {
        return err
    }

    i.LogImageEvent(imgID.String(), imgID.String(), events.ActionDelete)
    *records = append(*records, imagetypes.DeleteResponse{Deleted: imgID.String()})
    for _, removedLayer := range removedLayers {
        *records = append(*records, imagetypes.DeleteResponse{Deleted: removedLayer.ChainID.String()})
    }

    if !prune || parent == "" {
        return nil
    }

    // We need to prune the parent image. This means delete it if there are
    // no tags/digests referencing it and there are no containers using it (
    // either running or stopped).
    // Do not force prunings, but do so quietly (stopping on any encountered
    // conflicts).
    return i.imageDeleteHelper(parent, records, false, true, true)
}

// checkImageDeleteConflict determines whether there are any conflicts
// preventing deletion of the given image from this daemon. A hard conflict is
// any image which has the given image as a parent or any running container
// using the image. A soft conflict is any tags/digest referencing the given
// image or any stopped container using the image. If ignoreSoftConflicts is
// true, this function will not check for soft conflict conditions.
func (i *ImageService) checkImageDeleteConflict(imgID image.ID, mask conflictType) *imageDeleteConflict {
    // Check if the image has any descendant images.
    if mask&conflictDependentChild != 0 && len(i.imageStore.Children(imgID)) > 0 {
        return &imageDeleteConflict{
            hard:    true,
            imgID:   imgID,
            message: "image has dependent child images",
        }
    }

    if mask&conflictRunningContainer != 0 {
        // Check if any running container is using the image.
        running := func(c *container.Container) bool {
            return c.ImageID == imgID && c.IsRunning()
        }
        if ctr := i.containers.First(running); ctr != nil {
            return &imageDeleteConflict{
                imgID:   imgID,
                hard:    true,
                used:    true,
                message: fmt.Sprintf("image is being used by running container %s", stringid.TruncateID(ctr.ID)),
            }
        }
    }

    // Check if any repository tags/digest reference this image.
    if mask&conflictActiveReference != 0 && len(i.referenceStore.References(imgID.Digest())) > 0 {
        return &imageDeleteConflict{
            imgID:   imgID,
            message: "image is referenced in multiple repositories",
        }
    }

    if mask&conflictStoppedContainer != 0 {
        // Check if any stopped containers reference this image.
        stopped := func(c *container.Container) bool {
            return !c.IsRunning() && c.ImageID == imgID
        }
        if ctr := i.containers.First(stopped); ctr != nil {
            return &imageDeleteConflict{
                imgID:   imgID,
                used:    true,
                message: fmt.Sprintf("image is being used by stopped container %s", stringid.TruncateID(ctr.ID)),
            }
        }
    }

    return nil
}

// imageIsDangling returns whether the given image is "dangling" which means
// that there are no repository references to the given image and it has no
// child images.
func (i *ImageService) imageIsDangling(imgID image.ID) bool {
    return !(len(i.referenceStore.References(imgID.Digest())) > 0 || len(i.imageStore.Children(imgID)) > 0)
}