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Limit value size of additional annotation for avoiding unpack failure

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In containerd, there is a size limit for label size (4096 chars).
Currently if an image has many layers (> (4096-39)/72 > 56),
`containerd.io/snapshot/cri.image-layers` will hit the limit of label size and
the unpack will fail.
This commit fixes this by limiting the size of the annotation.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
This commit is contained in:
ktock
2020-09-10 19:40:49 +09:00
parent 35e623e6bf
commit e571fd864f
2 changed files with 75 additions and 11 deletions
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36
pkg/server/image_pull.go
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@@ -31,6 +31,7 @@ import (
"github.com/containerd/containerd"
"github.com/containerd/containerd/errdefs"
containerdimages "github.com/containerd/containerd/images"
"github.com/containerd/containerd/labels"
"github.com/containerd/containerd/log"
distribution "github.com/containerd/containerd/reference/docker"
"github.com/containerd/containerd/remotes/docker"
@@ -460,7 +461,7 @@ const (
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.
// parallel. Skipping some layers is allowed and only affects performance.
targetImageLayersLabel = "containerd.io/snapshot/cri.image-layers"
)
@@ -478,15 +479,6 @@ 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) {
@@ -495,7 +487,7 @@ func appendInfoHandlerWrapper(ref string) func(f containerdimages.Handler) conta
}
c.Annotations[targetRefLabel] = ref
c.Annotations[targetDigestLabel] = c.Digest.String()
c.Annotations[targetImageLayersLabel] = layers
c.Annotations[targetImageLayersLabel] = getLayers(ctx, targetImageLayersLabel, children[i:], labels.Validate)
}
}
}
@@ -503,3 +495,25 @@ func appendInfoHandlerWrapper(ref string) func(f containerdimages.Handler) conta
})
}
}
// getLayers returns comma-separated digests based on the passed list of
// descriptors. The returned list contains as many digests as possible as well
// as meets the label validation.
func getLayers(ctx context.Context, key string, descs []imagespec.Descriptor, validate func(k, v string) error) (layers string) {
var item string
for _, l := range descs {
if containerdimages.IsLayerType(l.MediaType) {
item = l.Digest.String()
if layers != "" {
item = "," + item
}
// This avoids the label hits the size limitation.
if err := validate(key, layers+item); err != nil {
log.G(ctx).WithError(err).WithField("label", key).Debugf("%q is omitted in the layers list", l.Digest.String())
break
}
layers += item
}
}
return
}