91 lines
3.0 KiB
Go
91 lines
3.0 KiB
Go
package daemon
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import (
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"io"
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"io/ioutil"
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"os"
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"github.com/containers/image/docker/tarfile"
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"github.com/containers/image/types"
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"github.com/docker/docker/client"
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"github.com/pkg/errors"
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"golang.org/x/net/context"
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)
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const temporaryDirectoryForBigFiles = "/var/tmp" // Do not use the system default of os.TempDir(), usually /tmp, because with systemd it could be a tmpfs.
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type daemonImageSource struct {
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ref daemonReference
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*tarfile.Source // Implements most of types.ImageSource
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tarCopyPath string
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}
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type layerInfo struct {
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path string
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size int64
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}
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// newImageSource returns a types.ImageSource for the specified image reference.
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// The caller must call .Close() on the returned ImageSource.
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//
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// It would be great if we were able to stream the input tar as it is being
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// sent; but Docker sends the top-level manifest, which determines which paths
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// to look for, at the end, so in we will need to seek back and re-read, several times.
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// (We could, perhaps, expect an exact sequence, assume that the first plaintext file
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// is the config, and that the following len(RootFS) files are the layers, but that feels
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// way too brittle.)
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func newImageSource(ctx *types.SystemContext, ref daemonReference) (types.ImageSource, error) {
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c, err := client.NewClient(client.DefaultDockerHost, "1.22", nil, nil) // FIXME: overridable host
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if err != nil {
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return nil, errors.Wrap(err, "Error initializing docker engine client")
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}
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// Per NewReference(), ref.StringWithinTransport() is either an image ID (config digest), or a !reference.NameOnly() reference.
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// Either way ImageSave should create a tarball with exactly one image.
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inputStream, err := c.ImageSave(context.TODO(), []string{ref.StringWithinTransport()})
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if err != nil {
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return nil, errors.Wrap(err, "Error loading image from docker engine")
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}
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defer inputStream.Close()
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// FIXME: use SystemContext here.
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tarCopyFile, err := ioutil.TempFile(temporaryDirectoryForBigFiles, "docker-daemon-tar")
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if err != nil {
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return nil, err
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}
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defer tarCopyFile.Close()
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succeeded := false
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defer func() {
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if !succeeded {
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os.Remove(tarCopyFile.Name())
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}
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}()
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if _, err := io.Copy(tarCopyFile, inputStream); err != nil {
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return nil, err
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}
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succeeded = true
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return &daemonImageSource{
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ref: ref,
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Source: tarfile.NewSource(tarCopyFile.Name()),
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tarCopyPath: tarCopyFile.Name(),
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}, nil
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}
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// Reference returns the reference used to set up this source, _as specified by the user_
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// (not as the image itself, or its underlying storage, claims). This can be used e.g. to determine which public keys are trusted for this image.
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func (s *daemonImageSource) Reference() types.ImageReference {
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return s.ref
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}
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// Close removes resources associated with an initialized ImageSource, if any.
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func (s *daemonImageSource) Close() error {
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return os.Remove(s.tarCopyPath)
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}
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// UpdatedLayerInfos() returns updated layer info that should be used when reading, in preference to values in the manifest, if specified.
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func (s *daemonImageSource) UpdatedLayerInfos() []types.BlobInfo {
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return nil
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}
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