151 lines
4 KiB
Go
151 lines
4 KiB
Go
package client
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import (
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"fmt"
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"io"
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"github.com/docker/docker-registry/storage"
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log "github.com/Sirupsen/logrus"
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)
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// simultaneousLayerPullWindow is the size of the parallel layer pull window.
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// A layer may not be pulled until the layer preceeding it by the length of the
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// pull window has been successfully pulled.
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const simultaneousLayerPullWindow = 4
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// Pull implements a client pull workflow for the image defined by the given
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// name and tag pair, using the given ObjectStore for local manifest and layer
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// storage
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func Pull(c Client, objectStore ObjectStore, name, tag string) error {
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manifest, err := c.GetImageManifest(name, tag)
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if err != nil {
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return err
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}
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log.WithField("manifest", manifest).Info("Pulled manifest")
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if len(manifest.FSLayers) != len(manifest.History) {
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return fmt.Errorf("Length of history not equal to number of layers")
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}
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if len(manifest.FSLayers) == 0 {
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return fmt.Errorf("Image has no layers")
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}
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errChans := make([]chan error, len(manifest.FSLayers))
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for i := range manifest.FSLayers {
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errChans[i] = make(chan error)
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}
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// To avoid leak of goroutines we must notify
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// pullLayer goroutines about a cancelation,
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// otherwise they will lock forever.
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cancelCh := make(chan struct{})
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// Iterate over each layer in the manifest, simultaneously pulling no more
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// than simultaneousLayerPullWindow layers at a time. If an error is
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// received from a layer pull, we abort the push.
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for i := 0; i < len(manifest.FSLayers)+simultaneousLayerPullWindow; i++ {
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dependentLayer := i - simultaneousLayerPullWindow
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if dependentLayer >= 0 {
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err := <-errChans[dependentLayer]
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if err != nil {
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log.WithField("error", err).Warn("Pull aborted")
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close(cancelCh)
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return err
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}
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}
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if i < len(manifest.FSLayers) {
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go func(i int) {
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select {
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case errChans[i] <- pullLayer(c, objectStore, name, manifest.FSLayers[i]):
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case <-cancelCh: // no chance to recv until cancelCh's closed
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}
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}(i)
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}
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}
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err = objectStore.WriteManifest(name, tag, manifest)
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if err != nil {
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log.WithFields(log.Fields{
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"error": err,
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"manifest": manifest,
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}).Warn("Unable to write image manifest")
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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 pullLayer(c Client, objectStore ObjectStore, name string, fsLayer storage.FSLayer) error {
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log.WithField("layer", fsLayer).Info("Pulling layer")
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layer, err := objectStore.Layer(fsLayer.BlobSum)
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if err != nil {
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log.WithFields(log.Fields{
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"error": err,
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"layer": fsLayer,
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}).Warn("Unable to write local layer")
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return err
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}
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layerWriter, err := layer.Writer()
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if err == ErrLayerAlreadyExists {
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log.WithField("layer", fsLayer).Info("Layer already exists")
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return nil
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}
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if err == ErrLayerLocked {
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log.WithField("layer", fsLayer).Info("Layer download in progress, waiting")
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layer.Wait()
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return nil
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}
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if err != nil {
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log.WithFields(log.Fields{
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"error": err,
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"layer": fsLayer,
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}).Warn("Unable to write local layer")
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return err
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}
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defer layerWriter.Close()
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if layerWriter.CurrentSize() > 0 {
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log.WithFields(log.Fields{
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"layer": fsLayer,
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"currentSize": layerWriter.CurrentSize(),
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"size": layerWriter.Size(),
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}).Info("Layer partially downloaded, resuming")
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}
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layerReader, length, err := c.GetBlob(name, fsLayer.BlobSum, layerWriter.CurrentSize())
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if err != nil {
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log.WithFields(log.Fields{
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"error": err,
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"layer": fsLayer,
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}).Warn("Unable to download layer")
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return err
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}
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defer layerReader.Close()
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layerWriter.SetSize(layerWriter.CurrentSize() + length)
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_, err = io.Copy(layerWriter, layerReader)
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if err != nil {
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log.WithFields(log.Fields{
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"error": err,
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"layer": fsLayer,
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}).Warn("Unable to download layer")
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return err
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}
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if layerWriter.CurrentSize() != layerWriter.Size() {
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log.WithFields(log.Fields{
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"size": layerWriter.Size(),
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"currentSize": layerWriter.CurrentSize(),
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"layer": fsLayer,
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}).Warn("Layer invalid size")
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return fmt.Errorf(
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"Wrote incorrect number of bytes for layer %v. Expected %d, Wrote %d",
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fsLayer, layerWriter.Size(), layerWriter.CurrentSize(),
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)
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}
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return nil
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}
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