Avoid a HEAD request for each layer in a v2 pull #18418
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aaronlehmann
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Note that the diff is a bit deceptive. This is simply removing: desc, err := blobs.Stat(context.Background(), di.digest)
if err != nil {
logrus.Debugf("Error statting layer: %v", err)
di.err <- err
return
}
di.size = desc.Sizeand adding, after the di.size, err = layerDownload.Seek(0, os.SEEK_END)
if err != nil {
di.err <- err
return
}
_, err = layerDownload.Seek(0, os.SEEK_SET)
if err != nil {
di.err <- err
return
}The diff captures the change in a more confusing way. |
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Nice! |
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LGTM |
We were calling Stat for each layer to get the size so we could indicate progress, but distribution/distribution#1226 made it possible to get the length from the GET request that Open initiates. Saving one round-trip per layer should make pull operations slightly faster and more robust. Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
aaronlehmann
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It just occurred to me that the first seek failing (presumably because there's no Content-Length header) shouldn't fail the whole download. It can still continue, but the progress output won't show a progress bar. I'm not sure if this will ever happen in practice, but it seems like a good idea to be robust to this situation. Sorry for changing the commit after a LGTM. |
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As a side effect, this tweak made the diff a lot easier to read ;) |
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LGTM |
1 similar comment
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LGTM |
calavera
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Dec 4, 2015
Avoid a HEAD request for each layer in a v2 pull
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We were calling Stat for each layer to get the size so we could indicate
progress, but distribution/distribution#1226 made it
possible to get the length from the GET request that Open initiates.
Saving one round-trip per layer should make pull operations slightly
faster and more robust.