129 lines
4.3 KiB
Go
129 lines
4.3 KiB
Go
/*
|
|
Copyright The containerd Authors.
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|
|
*/
|
|
|
|
package rootfs
|
|
|
|
import (
|
|
"crypto/rand"
|
|
"encoding/base64"
|
|
"fmt"
|
|
"time"
|
|
|
|
"github.com/containerd/containerd/diff"
|
|
"github.com/containerd/containerd/errdefs"
|
|
"github.com/containerd/containerd/log"
|
|
"github.com/containerd/containerd/snapshots"
|
|
"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"
|
|
)
|
|
|
|
// 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 snapshots.Snapshotter, a diff.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 snapshots.Snapshotter, a diff.Applier, opts ...snapshots.Opt) (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 %s exists", chainID)
|
|
return false, nil
|
|
} else if !errdefs.IsNotFound(err) {
|
|
return false, errors.Wrapf(err, "failed to stat snapshot %s", chainID)
|
|
}
|
|
|
|
key := fmt.Sprintf("extract-%s %s", uniquePart(), chainID)
|
|
|
|
// Prepare snapshot with from parent, label as root
|
|
mounts, err := sn.Prepare(ctx, key, parent.String(), opts...)
|
|
if err != nil {
|
|
//TODO: If is snapshot exists error, retry
|
|
return false, errors.Wrapf(err, "failed to prepare extraction snapshot %q", key)
|
|
}
|
|
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, opts...); err != nil {
|
|
if !errdefs.IsAlreadyExists(err) {
|
|
return false, errors.Wrapf(err, "failed to commit snapshot %s", key)
|
|
}
|
|
|
|
// Destination already exists, cleanup key and return without error
|
|
err = nil
|
|
if err := sn.Remove(ctx, key); err != nil {
|
|
return false, errors.Wrapf(err, "failed to cleanup aborted apply %s", key)
|
|
}
|
|
return false, nil
|
|
}
|
|
|
|
return true, nil
|
|
}
|
|
|
|
func uniquePart() string {
|
|
t := time.Now()
|
|
var b [3]byte
|
|
// Ignore read failures, just decreases uniqueness
|
|
rand.Read(b[:])
|
|
return fmt.Sprintf("%d-%s", t.Nanosecond(), base64.URLEncoding.EncodeToString(b[:]))
|
|
}
|