content: initial implementation of content store
After experimenting with pull, we've defined a transactional content store for verified storage of fetched items. A base component of containerkit, this will interact with both the runtime and distribution sides of the system, avoiding coupling. Blob access if provided through direct access to readonly files. Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day
parent
788e19d251
commit
9008471a84
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@ -0,0 +1,248 @@
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package content
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import (
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"io"
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"os"
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"path/filepath"
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"strings"
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"sync"
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"github.com/docker/distribution/digest"
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"github.com/pkg/errors"
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)
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var (
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ErrBlobNotFound = errors.New("blob not found")
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bufPool = sync.Pool{
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New: func() interface{} {
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return make([]byte, 32<<10)
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},
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}
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)
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// ContentStore is digest-keyed store for content. All data written into the
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// store is stored under a verifiable digest.
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//
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// ContentStore can generally support multi-reader, single-writer ingest of
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// data, including resumable ingest.
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type ContentStore struct {
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root string
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}
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func OpenContentStore(root string) (*ContentStore, error) {
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if err := os.MkdirAll(filepath.Join(root, "ingest"), 0777); err != nil && !os.IsExist(err) {
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return nil, err
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}
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return &ContentStore{
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root: root,
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}, nil
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}
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// OpenBlob opens the blob for reading identified by dgst.
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//
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// The opened blob may also implement seek. Callers can detect with io.Seeker.
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func OpenBlob(cs *ContentStore, dgst digest.Digest) (io.ReadCloser, error) {
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path, err := cs.GetPath(dgst)
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if err != nil {
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return nil, err
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}
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fp, err := os.Open(path)
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return fp, err
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}
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// WriteBlob writes data with the expected digest into the content store. If
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// expected already exists, the method returns immediately and the reader will
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// not be consumed.
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//
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// This is useful when the digest and size are known beforehand.
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//
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// Copy is buffered, so no need to wrap reader in buffered io.
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func WriteBlob(cs *ContentStore, r io.Reader, size int64, expected digest.Digest) error {
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cw, err := cs.Begin(expected.Hex())
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if err != nil {
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return err
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}
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buf := bufPool.Get().([]byte)
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defer bufPool.Put(buf)
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nn, err := io.CopyBuffer(cw, r, buf)
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if err != nil {
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return err
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}
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if nn != size {
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return errors.Errorf("failed size verification: %v != %v", nn, size)
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}
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if err := cw.Commit(size, expected); err != nil {
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return err
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}
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return nil
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}
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func (cs *ContentStore) GetPath(dgst digest.Digest) (string, error) {
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p := filepath.Join(cs.root, "blobs", dgst.Algorithm().String(), dgst.Hex())
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if _, err := os.Stat(p); err != nil {
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if os.IsNotExist(err) {
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return "", ErrBlobNotFound
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}
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return "", err
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}
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return p, nil
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}
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// Begin starts a new write transaction against the blob store.
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//
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// The argument `ref` is used to identify the transaction. It must be a valid
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// path component, meaning it has no `/` characters and no `:` (we'll ban
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// others fs characters, as needed).
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//
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// TODO(stevvooe): Figure out minimum common set of characters, basically common
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func (cs *ContentStore) Begin(ref string) (*ContentWriter, error) {
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path, data, err := cs.ingestPaths(ref)
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if err != nil {
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return nil, err
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}
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// use single path mkdir for this to ensure ref is only base path, in
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// addition to validation above.
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if err := os.Mkdir(path, 0755); err != nil {
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return nil, err
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}
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fp, err := os.OpenFile(data, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0666)
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if err != nil {
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return nil, errors.Wrap(err, "failed to open data file")
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}
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defer fp.Close()
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// re-open the file in append mode
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fp, err = os.OpenFile(data, os.O_WRONLY|os.O_APPEND, 0666)
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if err != nil {
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return nil, errors.Wrap(err, "error opening for append")
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}
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return &ContentWriter{
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cs: cs,
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fp: fp,
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path: path,
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digester: digest.Canonical.New(),
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}, nil
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}
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func (cs *ContentStore) Resume(ref string) (*ContentWriter, error) {
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path, data, err := cs.ingestPaths(ref)
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if err != nil {
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return nil, err
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}
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digester := digest.Canonical.New()
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// slow slow slow!!, send to goroutine
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fp, err := os.Open(data)
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offset, err := io.Copy(digester.Hash(), fp)
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if err != nil {
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return nil, err
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}
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defer fp.Close()
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fp1, err := os.OpenFile(data, os.O_WRONLY|os.O_APPEND, 0666)
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if err != nil {
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if os.IsNotExist(err) {
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return nil, errors.Wrap(err, "ingest does not exist")
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}
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return nil, errors.Wrap(err, "error opening for append")
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}
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return &ContentWriter{
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cs: cs,
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fp: fp1,
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path: path,
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offset: offset,
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digester: digester,
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}, nil
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}
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func (cs *ContentStore) ingestPaths(ref string) (string, string, error) {
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cref := filepath.Clean(ref)
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if cref != ref {
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return "", "", errors.Errorf("invalid path after clean")
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}
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fp := filepath.Join(cs.root, "ingest", ref)
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// ensure we don't escape root
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if !strings.HasPrefix(fp, cs.root) {
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return "", "", errors.Errorf("path %q escapes root", ref)
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}
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// ensure we are just a single path component
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if ref != filepath.Base(fp) {
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return "", "", errors.Errorf("ref must be a single path component")
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}
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return fp, filepath.Join(fp, "data"), nil
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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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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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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 data file failed")
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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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dgst := cw.digester.Digest()
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if 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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dpath := filepath.Join(apath, dgst.Hex())
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// clean up!!
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defer os.RemoveAll(cw.path)
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return os.Rename(filepath.Join(cw.path, "data"), dpath)
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}
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// Close the writer, leaving the progress in 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.
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func (cw *ContentWriter) Close() error {
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return cw.fp.Close()
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}
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@ -0,0 +1,117 @@
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package content
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import (
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"bufio"
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"bytes"
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"crypto/rand"
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"fmt"
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"io"
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"io/ioutil"
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"os"
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"path/filepath"
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"testing"
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"github.com/docker/distribution/digest"
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)
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func TestContentWriter(t *testing.T) {
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tmpdir, err := ioutil.TempDir("", "TestContentWriter-")
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cs, err := OpenContentStore(tmpdir)
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if err != nil {
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t.Fatal(err)
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}
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if _, err := os.Stat(filepath.Join(tmpdir, "ingest")); os.IsNotExist(err) {
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t.Fatal("ingest dir should be created", err)
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}
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cw, err := cs.Begin("myref")
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if err != nil {
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t.Fatal(err)
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}
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if err := cw.Close(); err != nil {
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t.Fatal(err)
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}
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// try to begin again with same ref, should fail
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cw, err = cs.Begin("myref")
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if err == nil {
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t.Fatal("expected error on repeated begin")
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}
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// reopen, so we can test things
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cw, err = cs.Resume("myref")
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if err != nil {
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t.Fatal(err)
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}
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p := make([]byte, 4<<20)
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if _, err := rand.Read(p); err != nil {
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t.Fatal(err)
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}
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expected := digest.FromBytes(p)
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checkCopy(t, int64(len(p)), cw, bufio.NewReader(ioutil.NopCloser(bytes.NewReader(p))))
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if err := cw.Commit(int64(len(p)), expected); err != nil {
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t.Fatal(err)
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}
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if err := cw.Close(); err != nil {
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t.Fatal(err)
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}
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cw, err = cs.Begin("aref")
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if err != nil {
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t.Fatal(err)
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}
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// now, attempt to write the same data again
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checkCopy(t, int64(len(p)), cw, bufio.NewReader(ioutil.NopCloser(bytes.NewReader(p))))
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if err := cw.Commit(int64(len(p)), expected); err != nil {
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t.Fatal(err)
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}
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path, err := cs.GetPath(expected)
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if err != nil {
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t.Fatal(err)
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}
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if path != filepath.Join(tmpdir, "blobs", expected.Algorithm().String(), expected.Hex()) {
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t.Fatalf("unxpected path: %q", path)
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}
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// read the data back, make sure its the same
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pp, err := ioutil.ReadFile(path)
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if err != nil {
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t.Fatal(err)
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}
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if !bytes.Equal(p, pp) {
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t.Fatal("mismatched data written to disk")
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}
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dumpDir(tmpdir)
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}
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func checkCopy(t *testing.T, size int64, dst io.Writer, src io.Reader) {
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nn, err := io.Copy(dst, src)
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if err != nil {
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t.Fatal(err)
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}
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if nn != size {
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t.Fatal("incorrect number of bytes copied")
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}
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}
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func dumpDir(root string) error {
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return filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
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if err != nil {
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return err
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}
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fmt.Println(fi.Mode(), path)
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return nil
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})
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}
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