// makeDownloadFuncFromDownload returns a func used by the TransferManager to
// handle a layer that was already seen in this image pull, or is currently being downloaded
func (ldm *LayerDownloader) makeDownloadFuncFromDownload(layer *ImageWithMeta, sourceDownload, parentDownload *downloadTransfer, layers []*ImageWithMeta) xfer.DoFunc {
return func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) xfer.Transfer {
d := &downloadTransfer{
Transfer: xfer.NewTransfer(),
layer: layer,
}
go func() {
defer close(progressChan)
<-start
close(inactive)
if parentDownload != nil {
select {
case <-d.Transfer.Context().Done():
d.err = errors.New("layer download cancelled")
return
case <-parentDownload.Done(): // wait for parent layer download to complete
}
if err := parentDownload.result(); err != nil {
d.err = err
return
}
}
// sourceDownload should have already finished if
// parentDownload finished, but wait for it explicitly
// to be sure.
select {
case <-d.Transfer.Context().Done():
d.err = errors.New("layer download cancelled")
return
case <-sourceDownload.Done():
}
if err := sourceDownload.result(); err != nil {
d.err = err
return
}
}()
return d
}
}
// makeDownloadFunc returns a func used by xfer.TransferManager to download a layer
func (ldm *LayerDownloader) makeDownloadFunc(layer *ImageWithMeta, ic *ImageC, parentDownload *downloadTransfer, layers []*ImageWithMeta) xfer.DoFunc {
return func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) xfer.Transfer {
d := &downloadTransfer{
Transfer: xfer.NewTransfer(),
layer: layer,
}
go func() {
defer func() {
close(progressChan)
// remove layer from cache if there was an error attempting to download
if d.err != nil {
LayerCache().Remove(layer.ID)
}
}()
progressOutput := progress.ChanOutput(progressChan)
// wait for TransferManager to give the go-ahead
select {
case <-start:
default:
progress.Update(progressOutput, layer.String(), "Waiting")
<-start
}
if parentDownload != nil {
// bail if parent download failed or was cancelled
select {
case <-parentDownload.Done():
if err := parentDownload.result(); err != nil {
d.err = err
return
}
default:
}
}
// fetch blob
diffID, err := FetchImageBlob(d.Transfer.Context(), ic.Options, layer, progressOutput)
if err != nil {
d.err = fmt.Errorf("%s/%s returned %s", ic.Image, layer.ID, err)
return
}
layer.DiffID = diffID
close(inactive)
if parentDownload != nil {
select {
case <-d.Transfer.Context().Done():
d.err = errors.New("layer download cancelled")
return
default:
<-parentDownload.Done() // block until parent download completes
}
if err := parentDownload.result(); err != nil {
d.err = err
return
}
}
// is this the leaf layer?
imageLayer := layer.ID == layers[0].ID
// if this is the leaf layer, we are done and can now create the image config
if imageLayer {
imageConfig, err := ic.CreateImageConfig(layers)
if err != nil {
d.err = err
return
}
// cache and persist the image
cache.ImageCache().Add(&imageConfig)
cache.ImageCache().Save()
// place calculated ImageID in struct
ic.ImageID = imageConfig.ImageID
if err = updateRepositoryCache(ic); err != nil {
d.err = err
return
}
}
ldm.m.Lock()
defer ldm.m.Unlock()
// Write blob to the storage layer
if err := ic.WriteImageBlob(layer, progressOutput, imageLayer); err != nil {
d.err = err
return
}
// mark the layer as finished downloading
LayerCache().Commit(layer)
ldm.unregisterDownload(layer)
}()
return d
}
}