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snapshot.go
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snapshot.go
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package metadata
import (
"context"
"fmt"
"strings"
"github.com/boltdb/bolt"
"github.com/containerd/containerd/errdefs"
"github.com/containerd/containerd/mount"
"github.com/containerd/containerd/namespaces"
"github.com/containerd/containerd/snapshot"
"github.com/pkg/errors"
)
type snapshotter struct {
snapshot.Snapshotter
name string
db *bolt.DB
}
// NewSnapshotter returns a new Snapshotter which namespaces the given snapshot
// using the provided name and metadata store.
func NewSnapshotter(db *bolt.DB, name string, sn snapshot.Snapshotter) snapshot.Snapshotter {
return &snapshotter{
Snapshotter: sn,
name: name,
db: db,
}
}
func createKey(id uint64, namespace, key string) string {
return fmt.Sprintf("%s/%d/%s", namespace, id, key)
}
func trimKey(key string) string {
parts := strings.SplitN(key, "/", 3)
if len(parts) < 3 {
return ""
}
return parts[2]
}
func getKey(tx *bolt.Tx, ns, name, key string) string {
bkt := getSnapshotterBucket(tx, ns, name)
if bkt == nil {
return ""
}
v := bkt.Get([]byte(key))
if len(v) == 0 {
return ""
}
return string(v)
}
func (s *snapshotter) resolveKey(ctx context.Context, key string) (string, error) {
ns, err := namespaces.NamespaceRequired(ctx)
if err != nil {
return "", err
}
var id string
if err := view(ctx, s.db, func(tx *bolt.Tx) error {
id = getKey(tx, ns, s.name, key)
if id == "" {
return errors.Wrapf(errdefs.ErrNotFound, "snapshot %v does not exist", key)
}
return nil
}); err != nil {
return "", err
}
return id, nil
}
func (s *snapshotter) Stat(ctx context.Context, key string) (snapshot.Info, error) {
bkey, err := s.resolveKey(ctx, key)
if err != nil {
return snapshot.Info{}, err
}
info, err := s.Snapshotter.Stat(ctx, bkey)
if err != nil {
return snapshot.Info{}, err
}
info.Name = trimKey(info.Name)
if info.Parent != "" {
info.Parent = trimKey(info.Parent)
}
return info, nil
}
func (s *snapshotter) Usage(ctx context.Context, key string) (snapshot.Usage, error) {
bkey, err := s.resolveKey(ctx, key)
if err != nil {
return snapshot.Usage{}, err
}
return s.Snapshotter.Usage(ctx, bkey)
}
func (s *snapshotter) Mounts(ctx context.Context, key string) ([]mount.Mount, error) {
bkey, err := s.resolveKey(ctx, key)
if err != nil {
return nil, err
}
return s.Snapshotter.Mounts(ctx, bkey)
}
func (s *snapshotter) Prepare(ctx context.Context, key, parent string) ([]mount.Mount, error) {
return s.createSnapshot(ctx, key, parent, false)
}
func (s *snapshotter) View(ctx context.Context, key, parent string) ([]mount.Mount, error) {
return s.createSnapshot(ctx, key, parent, true)
}
func (s *snapshotter) createSnapshot(ctx context.Context, key, parent string, readonly bool) ([]mount.Mount, error) {
ns, err := namespaces.NamespaceRequired(ctx)
if err != nil {
return nil, err
}
var m []mount.Mount
if err := update(ctx, s.db, func(tx *bolt.Tx) error {
bkt, err := createSnapshotterBucket(tx, ns, s.name)
if err != nil {
return err
}
bkey := string(bkt.Get([]byte(key)))
if bkey != "" {
return errors.Wrapf(errdefs.ErrAlreadyExists, "snapshot %v already exists", key)
}
var bparent string
if parent != "" {
bparent = string(bkt.Get([]byte(parent)))
if bparent == "" {
return errors.Wrapf(errdefs.ErrNotFound, "snapshot %v does not exist", parent)
}
}
sid, err := bkt.NextSequence()
if err != nil {
return err
}
bkey = createKey(sid, ns, key)
if err := bkt.Put([]byte(key), []byte(bkey)); err != nil {
return err
}
// TODO: Consider doing this outside of transaction to lessen
// metadata lock time
if readonly {
m, err = s.Snapshotter.View(ctx, bkey, bparent)
} else {
m, err = s.Snapshotter.Prepare(ctx, bkey, bparent)
}
return err
}); err != nil {
return nil, err
}
return m, nil
}
func (s *snapshotter) Commit(ctx context.Context, name, key string) error {
ns, err := namespaces.NamespaceRequired(ctx)
if err != nil {
return err
}
return update(ctx, s.db, func(tx *bolt.Tx) error {
bkt := getSnapshotterBucket(tx, ns, s.name)
if bkt == nil {
return errors.Wrapf(errdefs.ErrNotFound, "snapshot %v does not exist", key)
}
nameKey := string(bkt.Get([]byte(name)))
if nameKey != "" {
return errors.Wrapf(errdefs.ErrAlreadyExists, "snapshot %v already exists", name)
}
bkey := string(bkt.Get([]byte(key)))
if bkey == "" {
return errors.Wrapf(errdefs.ErrNotFound, "snapshot %v does not exist", key)
}
sid, err := bkt.NextSequence()
if err != nil {
return err
}
nameKey = createKey(sid, ns, name)
if err := bkt.Put([]byte(name), []byte(nameKey)); err != nil {
return err
}
if err := bkt.Delete([]byte(key)); err != nil {
return err
}
// TODO: Consider doing this outside of transaction to lessen
// metadata lock time
return s.Snapshotter.Commit(ctx, nameKey, bkey)
})
}
func (s *snapshotter) Remove(ctx context.Context, key string) error {
ns, err := namespaces.NamespaceRequired(ctx)
if err != nil {
return err
}
return update(ctx, s.db, func(tx *bolt.Tx) error {
bkt := getSnapshotterBucket(tx, ns, s.name)
if bkt == nil {
return errors.Wrapf(errdefs.ErrNotFound, "snapshot %v does not exist", key)
}
bkey := string(bkt.Get([]byte(key)))
if bkey == "" {
return errors.Wrapf(errdefs.ErrNotFound, "snapshot %v does not exist", key)
}
if err := bkt.Delete([]byte(key)); err != nil {
return err
}
return s.Snapshotter.Remove(ctx, bkey)
})
}
func (s *snapshotter) Walk(ctx context.Context, fn func(context.Context, snapshot.Info) error) error {
ns, err := namespaces.NamespaceRequired(ctx)
if err != nil {
return err
}
var keys []string
if err := view(ctx, s.db, func(tx *bolt.Tx) error {
bkt := getSnapshotterBucket(tx, ns, s.name)
if bkt == nil {
return nil
}
bkt.ForEach(func(k, v []byte) error {
if len(v) > 0 {
keys = append(keys, string(v))
}
return nil
})
return nil
}); err != nil {
return err
}
for _, k := range keys {
info, err := s.Snapshotter.Stat(ctx, k)
if err != nil {
return err
}
info.Name = trimKey(info.Name)
if info.Parent != "" {
info.Parent = trimKey(info.Parent)
}
if err := fn(ctx, info); err != nil {
return err
}
}
return nil
}