098ff94b24
Remove rootfs service in place of snapshot service. Adds diff service for extracting and creating diffs. Diff creation is not yet implemented. This service allows pulling or creating images without needing root access to mount. Additionally in the future this will allow containerd to ensure extractions happen safely in a chroot if needed. Signed-off-by: Derek McGowan <derek@mcgstyle.net>
85 lines
2.4 KiB
Go
85 lines
2.4 KiB
Go
package rootfs
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import (
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"context"
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"fmt"
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"github.com/containerd/containerd"
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"github.com/containerd/containerd/log"
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"github.com/containerd/containerd/snapshot"
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"github.com/opencontainers/go-digest"
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"github.com/opencontainers/image-spec/identity"
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ocispec "github.com/opencontainers/image-spec/specs-go/v1"
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"github.com/pkg/errors"
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)
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type Applier interface {
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Apply(context.Context, ocispec.Descriptor, []containerd.Mount) (ocispec.Descriptor, error)
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}
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type Layer struct {
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Diff ocispec.Descriptor
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Blob ocispec.Descriptor
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}
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func ApplyLayers(ctx context.Context, layers []Layer, sn snapshot.Snapshotter, a Applier) (digest.Digest, error) {
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var chain []digest.Digest
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for _, layer := range layers {
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if err := applyLayer(ctx, layer, chain, sn, a); err != nil {
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// TODO: possibly wait and retry if extraction of same chain id was in progress
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return "", err
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}
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chain = append(chain, layer.Diff.Digest)
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}
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return identity.ChainID(chain), nil
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}
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func applyLayer(ctx context.Context, layer Layer, chain []digest.Digest, sn snapshot.Snapshotter, a Applier) error {
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var (
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parent = identity.ChainID(chain)
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chainID = identity.ChainID(append(chain, layer.Diff.Digest))
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diff ocispec.Descriptor
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)
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_, err := sn.Stat(ctx, chainID.String())
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if err == nil {
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log.G(ctx).Debugf("Extraction not needed, layer snapshot exists")
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return nil
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} else if !snapshot.IsNotExist(err) {
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return errors.Wrap(err, "failed to stat snapshot")
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}
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key := fmt.Sprintf("extract %s", chainID)
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// Prepare snapshot with from parent
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mounts, err := sn.Prepare(ctx, key, parent.String())
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if err != nil {
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//TODO: If is snapshot exists error, retry
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return errors.Wrap(err, "failed to prepare extraction layer")
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}
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defer func() {
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if err != nil {
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log.G(ctx).WithError(err).WithField("key", key).Infof("Apply failure, attempting cleanup")
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if rerr := sn.Remove(ctx, key); rerr != nil {
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log.G(ctx).WithError(rerr).Warnf("Extraction snapshot %q removal failed: %v", key)
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}
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}
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}()
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diff, err = a.Apply(ctx, layer.Blob, mounts)
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if err != nil {
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return errors.Wrapf(err, "failed to extract layer %s", layer.Diff.Digest)
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}
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if diff.Digest != layer.Diff.Digest {
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err = errors.Errorf("wrong diff id calculated on extraction %q", diff.Digest)
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return err
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}
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if err = sn.Commit(ctx, chainID.String(), key); err != nil {
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return errors.Wrapf(err, "failed to commit snapshot %s", parent)
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}
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return nil
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}
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