145 lines
3.5 KiB
Go
145 lines
3.5 KiB
Go
package content
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import (
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"os"
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"path/filepath"
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"time"
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"github.com/docker/containerd/log"
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"github.com/nightlyone/lockfile"
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"github.com/opencontainers/go-digest"
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"github.com/pkg/errors"
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)
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// writer represents a write transaction against the blob store.
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type writer struct {
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s *Store
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fp *os.File // opened data file
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lock lockfile.Lockfile
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path string // path to writer dir
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ref string // ref key
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offset int64
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total int64
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digester digest.Digester
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startedAt time.Time
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updatedAt time.Time
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}
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func (w *writer) Status() (Status, error) {
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return Status{
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Ref: w.ref,
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Offset: w.offset,
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Total: w.total,
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StartedAt: w.startedAt,
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UpdatedAt: w.updatedAt,
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}, nil
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}
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// Digest returns the current digest of the content, up to the current write.
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//
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// Cannot be called concurrently with `Write`.
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func (w *writer) Digest() digest.Digest {
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return w.digester.Digest()
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}
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// Write p to the transaction.
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//
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// Note that writes are unbuffered to the backing file. When writing, it is
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// recommended to wrap in a bufio.Writer or, preferably, use io.CopyBuffer.
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func (w *writer) Write(p []byte) (n int, err error) {
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n, err = w.fp.Write(p)
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w.digester.Hash().Write(p[:n])
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w.offset += int64(len(p))
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w.updatedAt = time.Now()
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return n, err
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}
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func (w *writer) Commit(size int64, expected digest.Digest) error {
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if err := w.fp.Sync(); err != nil {
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return errors.Wrap(err, "sync failed")
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}
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fi, err := w.fp.Stat()
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if err != nil {
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return errors.Wrap(err, "stat on ingest file failed")
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}
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// change to readonly, more important for read, but provides _some_
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// protection from this point on. We use the existing perms with a mask
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// only allowing reads honoring the umask on creation.
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//
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// This removes write and exec, only allowing read per the creation umask.
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if err := w.fp.Chmod((fi.Mode() & os.ModePerm) &^ 0333); err != nil {
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return errors.Wrap(err, "failed to change ingest file permissions")
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}
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if size > 0 && size != fi.Size() {
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return errors.Errorf("%q failed size validation: %v != %v", w.ref, fi.Size(), size)
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}
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if err := w.fp.Close(); err != nil {
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return errors.Wrap(err, "failed closing ingest")
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}
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dgst := w.digester.Digest()
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if expected != "" && expected != dgst {
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return errors.Errorf("unexpected digest: %v != %v", dgst, expected)
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}
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var (
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ingest = filepath.Join(w.path, "data")
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target = w.s.blobPath(dgst)
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)
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// make sure parent directories of blob exist
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if err := os.MkdirAll(filepath.Dir(target), 0755); err != nil {
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return err
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}
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// clean up!!
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defer os.RemoveAll(w.path)
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if err := os.Rename(ingest, target); err != nil {
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if os.IsExist(err) {
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// collision with the target file!
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return ErrExists
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}
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return err
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}
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unlock(w.lock)
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w.fp = nil
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return nil
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}
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// Close the writer, flushing any unwritten data and leaving the progress in
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// tact.
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//
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// If one needs to resume the transaction, a new writer can be obtained from
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// `ContentStore.Resume` using the same key. The write can then be continued
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// from it was left off.
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//
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// To abandon a transaction completely, first call close then `Store.Remove` to
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// clean up the associated resources.
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func (cw *writer) Close() (err error) {
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if err := unlock(cw.lock); err != nil {
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log.L.Debug("unlock failed: %v", err)
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}
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if cw.fp != nil {
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cw.fp.Sync()
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return cw.fp.Close()
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}
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return nil
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}
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func (w *writer) Truncate(size int64) error {
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if size != 0 {
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return errors.New("Truncate: unsupported size")
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}
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w.offset = 0
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w.digester.Hash().Reset()
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return w.fp.Truncate(0)
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}
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