4f388e0e27
Clarifies role of varies rootfs functions as well as their return values. Signed-off-by: Derek McGowan <derek@mcgstyle.net>
98 lines
3.3 KiB
Go
98 lines
3.3 KiB
Go
package rootfs
|
|
|
|
import (
|
|
"fmt"
|
|
|
|
"github.com/containerd/containerd/errdefs"
|
|
"github.com/containerd/containerd/log"
|
|
"github.com/containerd/containerd/mount"
|
|
"github.com/containerd/containerd/snapshot"
|
|
"github.com/opencontainers/go-digest"
|
|
"github.com/opencontainers/image-spec/identity"
|
|
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
|
|
"github.com/pkg/errors"
|
|
"golang.org/x/net/context"
|
|
)
|
|
|
|
// Applier is used to apply a descriptor of a layer diff on top of mounts.
|
|
type Applier interface {
|
|
Apply(context.Context, ocispec.Descriptor, []mount.Mount) (ocispec.Descriptor, error)
|
|
}
|
|
|
|
// Layer represents the descriptors for a layer diff. These descriptions
|
|
// include the descriptor for the uncompressed tar diff as well as a blob
|
|
// used to transport that tar. The blob descriptor may or may not describe
|
|
// a compressed object.
|
|
type Layer struct {
|
|
Diff ocispec.Descriptor
|
|
Blob ocispec.Descriptor
|
|
}
|
|
|
|
// ApplyLayers applies all the layers using the given snapshotter and applier.
|
|
// The returned result is a chain id digest representing all the applied layers.
|
|
// Layers are applied in order they are given, making the first layer the
|
|
// bottom-most layer in the layer chain.
|
|
func ApplyLayers(ctx context.Context, layers []Layer, sn snapshot.Snapshotter, a Applier) (digest.Digest, error) {
|
|
var chain []digest.Digest
|
|
for _, layer := range layers {
|
|
if _, err := ApplyLayer(ctx, layer, chain, sn, a); err != nil {
|
|
// TODO: possibly wait and retry if extraction of same chain id was in progress
|
|
return "", err
|
|
}
|
|
|
|
chain = append(chain, layer.Diff.Digest)
|
|
}
|
|
return identity.ChainID(chain), nil
|
|
}
|
|
|
|
// ApplyLayer applies a single layer on top of the given provided layer chain,
|
|
// using the provided snapshotter and applier. If the layer was unpacked true
|
|
// is returned, if the layer already exists false is returned.
|
|
func ApplyLayer(ctx context.Context, layer Layer, chain []digest.Digest, sn snapshot.Snapshotter, a Applier) (bool, error) {
|
|
var (
|
|
parent = identity.ChainID(chain)
|
|
chainID = identity.ChainID(append(chain, layer.Diff.Digest))
|
|
diff ocispec.Descriptor
|
|
)
|
|
|
|
_, err := sn.Stat(ctx, chainID.String())
|
|
if err == nil {
|
|
log.G(ctx).Debugf("Extraction not needed, layer snapshot exists")
|
|
return false, nil
|
|
} else if !errdefs.IsNotFound(err) {
|
|
return false, errors.Wrap(err, "failed to stat snapshot")
|
|
}
|
|
|
|
key := fmt.Sprintf("extract %s", chainID)
|
|
|
|
// Prepare snapshot with from parent
|
|
mounts, err := sn.Prepare(ctx, key, parent.String())
|
|
if err != nil {
|
|
//TODO: If is snapshot exists error, retry
|
|
return false, errors.Wrap(err, "failed to prepare extraction layer")
|
|
}
|
|
defer func() {
|
|
if err != nil {
|
|
log.G(ctx).WithError(err).WithField("key", key).Infof("Apply failure, attempting cleanup")
|
|
if rerr := sn.Remove(ctx, key); rerr != nil {
|
|
log.G(ctx).WithError(rerr).Warnf("Extraction snapshot %q removal failed", key)
|
|
}
|
|
}
|
|
}()
|
|
|
|
diff, err = a.Apply(ctx, layer.Blob, mounts)
|
|
if err != nil {
|
|
return false, errors.Wrapf(err, "failed to extract layer %s", layer.Diff.Digest)
|
|
}
|
|
if diff.Digest != layer.Diff.Digest {
|
|
err = errors.Errorf("wrong diff id calculated on extraction %q", diff.Digest)
|
|
return false, err
|
|
}
|
|
|
|
if err = sn.Commit(ctx, chainID.String(), key); err != nil {
|
|
return false, errors.Wrapf(err, "failed to commit snapshot %s", parent)
|
|
}
|
|
|
|
return true, nil
|
|
}
|