682151b166
To support resumable download, the fetcher for a remote must implement `io.Seeker`. If implemented the `content.Copy` function will detect the seeker and begin from where the download was terminated by a previous attempt. Signed-off-by: Stephen J Day <stephen.day@docker.com>
126 lines
2.6 KiB
Go
126 lines
2.6 KiB
Go
package docker
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import (
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"bytes"
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"io"
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"io/ioutil"
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"github.com/containerd/containerd/errdefs"
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"github.com/containerd/containerd/log"
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"github.com/pkg/errors"
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)
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type httpReadSeeker struct {
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size int64
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offset int64
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rc io.ReadCloser
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open func(offset int64) (io.ReadCloser, error)
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closed bool
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}
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func newHTTPReadSeeker(size int64, open func(offset int64) (io.ReadCloser, error)) (io.ReadCloser, error) {
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return &httpReadSeeker{
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size: size,
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open: open,
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}, nil
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}
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func (hrs *httpReadSeeker) Read(p []byte) (n int, err error) {
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if hrs.closed {
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return 0, io.EOF
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}
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rd, err := hrs.reader()
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if err != nil {
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return 0, err
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}
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n, err = rd.Read(p)
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hrs.offset += int64(n)
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return
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}
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func (hrs *httpReadSeeker) Close() error {
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if hrs.closed {
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return nil
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}
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hrs.closed = true
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if hrs.rc != nil {
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return hrs.rc.Close()
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}
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return nil
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}
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func (hrs *httpReadSeeker) Seek(offset int64, whence int) (int64, error) {
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if hrs.closed {
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return 0, errors.Wrap(errdefs.ErrUnavailable, "Fetcher.Seek: closed")
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}
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abs := hrs.offset
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switch whence {
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case io.SeekStart:
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abs = offset
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case io.SeekCurrent:
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abs += offset
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case io.SeekEnd:
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abs = hrs.size + offset
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default:
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return 0, errors.Wrap(errdefs.ErrInvalidArgument, "Fetcher.Seek: invalid whence")
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}
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if abs < 0 {
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return 0, errors.Wrapf(errdefs.ErrInvalidArgument, "Fetcher.Seek: negative offset")
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}
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if abs != hrs.offset {
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if hrs.rc != nil {
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if err := hrs.rc.Close(); err != nil {
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log.L.WithError(err).Errorf("Fetcher.Seek: failed to close ReadCloser")
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}
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hrs.rc = nil
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}
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hrs.offset = abs
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}
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return hrs.offset, nil
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}
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func (hrs *httpReadSeeker) reader() (io.Reader, error) {
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if hrs.rc != nil {
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return hrs.rc, nil
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}
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if hrs.offset < hrs.size {
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// only try to reopen the body request if we are seeking to a value
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// less than the actual size.
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if hrs.open == nil {
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return nil, errors.Wrapf(errdefs.ErrNotImplemented, "cannot open")
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}
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rc, err := hrs.open(hrs.offset)
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if err != nil {
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return nil, errors.Wrapf(err, "httpReaderSeeker: failed open")
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}
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if hrs.rc != nil {
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if err := hrs.rc.Close(); err != nil {
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log.L.WithError(err).Errorf("httpReadSeeker: failed to close ReadCloser")
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}
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}
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hrs.rc = rc
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} else {
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// There is an edge case here where offset == size of the content. If
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// we seek, we will probably get an error for content that cannot be
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// sought (?). In that case, we should err on committing the content,
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// as the length is already satisified but we just return the empty
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// reader instead.
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hrs.rc = ioutil.NopCloser(bytes.NewReader([]byte{}))
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}
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return hrs.rc, nil
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}
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