118 lines
3.1 KiB
Go
118 lines
3.1 KiB
Go
package snapshot
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import (
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"fmt"
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"io/ioutil"
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"os"
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"path/filepath"
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"github.com/docker/containerd"
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"github.com/docker/docker/pkg/archive"
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"github.com/pkg/errors"
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)
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type Naive struct {
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root string
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// TODO(stevvooe): Very lazy copying from the overlay driver. We'll have to
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// put *all* of this on disk in an easy to access format.
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active map[string]activeNaiveSnapshot
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parents map[string]string // mirror of what is on disk
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}
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type activeNaiveSnapshot struct {
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parent string
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metadata string
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}
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func NewNaive(root string) (*Naive, error) {
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if err := os.MkdirAll(root, 0777); err != nil {
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return nil, err
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}
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// TODO(stevvooe): Recover active transactions.
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return &Naive{
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root: root,
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active: make(map[string]activeNaiveSnapshot),
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parents: make(map[string]string),
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}, nil
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}
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// Prepare works per the snapshot specification.
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//
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// For the naive driver, the data is checked out directly into dst and no
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// mounts are returned.
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func (lm *Naive) Prepare(dst, parent string) ([]containerd.Mount, error) {
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metadataRoot, err := ioutil.TempDir(lm.root, "active-")
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if err != nil {
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return nil, errors.Wrap(err, "failed to created transaction dir")
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}
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// TODO(stevvooe): Write in driver metadata so it can be identified,
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// probably part of common manager type.
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if err := ioutil.WriteFile(filepath.Join(metadataRoot, "target"), []byte(dst), 0777); err != nil {
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return nil, errors.Wrap(err, "failed to write target to disk")
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}
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if parent != "" {
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if _, ok := lm.parents[parent]; !ok {
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return nil, errors.Wrap(err, "specified parent does not exist")
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}
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if err := ioutil.WriteFile(filepath.Join(metadataRoot, "parent"), []byte(parent), 0777); err != nil {
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return nil, errors.Wrap(err, "error specifying parent")
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}
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// Now, we copy the parent filesystem, just a directory, into dst.
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if err := archive.CopyWithTar(filepath.Join(parent, "data"), dst); err != nil { // note: src, dst args, ick!
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return nil, errors.Wrap(err, "copying of parent failed")
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}
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}
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lm.active[dst] = activeNaiveSnapshot{
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parent: parent,
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metadata: metadataRoot,
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}
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return nil, nil // no mounts!!
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}
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// Commit just moves the metadata directory to the diff location.
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func (lm *Naive) Commit(diff, dst string) error {
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active, ok := lm.active[dst]
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if !ok {
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return errors.Errorf("%v is not an active transaction", dst)
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}
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// Move the data into our metadata directory, we could probably save disk
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// space if we just saved the diff, but let's get something working.
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if err := archive.CopyWithTar(dst, filepath.Join(active.metadata, "data")); err != nil { // note: src, dst args, ick!
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return errors.Wrap(err, "copying of parent failed")
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}
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if err := os.Rename(active.metadata, diff); err != nil {
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return errors.Wrap(err, "failed to rename metadata into diff")
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}
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lm.parents[diff] = active.parent
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delete(lm.active, dst)
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return nil
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}
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func (lm *Naive) Rollback(dst string) error {
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active, ok := lm.active[dst]
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if !ok {
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return fmt.Errorf("%q must be an active snapshot", dst)
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}
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delete(lm.active, dst)
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return os.RemoveAll(active.metadata)
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}
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func (lm *Naive) Parent(diff string) string {
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return lm.parents[diff]
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}
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