112 lines
2.8 KiB
Go
112 lines
2.8 KiB
Go
package content
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import (
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"log"
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"os"
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"path/filepath"
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"github.com/docker/distribution/digest"
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"github.com/nightlyone/lockfile"
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"github.com/pkg/errors"
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)
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// ContentWriter represents a write transaction against the blob store.
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//
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//
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type ContentWriter struct {
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cs *ContentStore
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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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offset int64
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digester digest.Digester
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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 (cw *ContentWriter) Write(p []byte) (n int, err error) {
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n, err = cw.fp.Write(p)
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cw.digester.Hash().Write(p[:n])
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return n, err
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}
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func (cw *ContentWriter) Commit(size int64, expected digest.Digest) error {
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if err := cw.fp.Sync(); err != nil {
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return errors.Wrap(err, "sync failed")
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}
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fi, err := cw.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 := cw.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 != fi.Size() {
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return errors.Errorf("failed size validation: %v != %v", fi.Size(), size)
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}
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if err := cw.fp.Close(); err != nil {
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return errors.Wrap(err, "failed closing ingest")
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}
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dgst := cw.digester.Digest()
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// TODO(stevvooe): Correctly handle missing expected digest or allow no
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// expected digest at commit time.
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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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apath := filepath.Join(cw.cs.root, "blobs", dgst.Algorithm().String())
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if err := os.MkdirAll(apath, 0755); err != nil {
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return err
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}
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var (
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ingest = filepath.Join(cw.path, "data")
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target = filepath.Join(apath, dgst.Hex())
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)
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// clean up!!
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defer os.RemoveAll(cw.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 nil
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}
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return err
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}
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unlock(cw.lock)
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cw.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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func (cw *ContentWriter) Close() (err error) {
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if err := unlock(cw.lock); err != nil {
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log.Printf("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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