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Pass chained layer digests to snapshotter for parallel snapshot preparation

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Currently, CRI plugin passes each layer digest to remote snapshotters
sequentially, which leads to sequential snapshots preparation. But it costs
extra time especially for remote snapshotters which need to connect to the
remote backend store (e.g. registries) for checking the snapshot existence on
each preparation.

This commit solves this problem by introducing new label
`containerd.io/snapshot/cri.chain` for passing all layer digests in an image to
snapshotters and by allowing them to prepare these snapshots in parallel, which
leads to speed up the preparation.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
This commit is contained in:
ktock 2020-04-27 16:42:20 +09:00
parent 4ea4ca99c7
commit ca661c8dc9
1 changed files with 14 additions and 0 deletions
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14
pkg/server/image_pull.go
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@ -455,6 +455,10 @@ const (
// targetDigestLabel is a label which contains layer digest and will be passed
// to snapshotters.
targetDigestLabel = "containerd.io/snapshot/cri.layer-digest"
// targetImageLayersLabel is a label which contains layer digests contained in
// the target image and will be passed to snapshotters for preparing layers in
// parallel.
targetImageLayersLabel = "containerd.io/snapshot/cri.image-layers"
)
// appendInfoHandlerWrapper makes a handler which appends some basic information
@ -471,6 +475,15 @@ func appendInfoHandlerWrapper(ref string) func(f containerdimages.Handler) conta
}
switch desc.MediaType {
case imagespec.MediaTypeImageManifest, containerdimages.MediaTypeDockerSchema2Manifest:
var layers string
for _, c := range children {
if containerdimages.IsLayerType(c.MediaType) {
layers += fmt.Sprintf("%s,", c.Digest.String())
}
}
if len(layers) >= 1 {
layers = layers[:len(layers)-1]
}
for i := range children {
c := &children[i]
if containerdimages.IsLayerType(c.MediaType) {
@ -479,6 +492,7 @@ func appendInfoHandlerWrapper(ref string) func(f containerdimages.Handler) conta
}
c.Annotations[targetRefLabel] = ref
c.Annotations[targetDigestLabel] = c.Digest.String()
c.Annotations[targetImageLayersLabel] = layers
}
}
}