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storage, dest: clarify when TOCDigest is used
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This update introduces an enhancement in the blob handling mechanism,
specifically by separating the TOC digest from the
uncompressed/compressed digest.

Follow-up for: containers#1080.

Signed-off-by: Giuseppe Scrivano <[email protected]>
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giuseppe committed Jan 26, 2024
1 parent 32f3239 commit 73632a7
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Showing 3 changed files with 211 additions and 132 deletions.
15 changes: 13 additions & 2 deletions copy/single.go
Original file line number Diff line number Diff line change
Expand Up @@ -696,11 +696,16 @@ func (ic *imageCopier) copyLayer(ctx context.Context, srcInfo types.BlobInfo, to
originalCompression = srcInfo.CompressionAlgorithm
}

var tocDigest digest.Digest

// Check if we have a chunked layer in storage that's based on that blob. These layers are stored by their TOC digest.
tocDigest, err := chunkedToc.GetTOCDigest(srcInfo.Annotations)
d, err := chunkedToc.GetTOCDigest(srcInfo.Annotations)
if err != nil {
return types.BlobInfo{}, "", err
}
if d != nil {
tocDigest = *d
}

reused, reusedBlob, err := ic.c.dest.TryReusingBlobWithOptions(ctx, srcInfo, private.TryReusingBlobOptions{
Cache: ic.c.blobInfoCache,
Expand All @@ -718,7 +723,13 @@ func (ic *imageCopier) copyLayer(ctx context.Context, srcInfo types.BlobInfo, to
if reused {
logrus.Debugf("Skipping blob %s (already present):", srcInfo.Digest)
func() { // A scope for defer
bar := ic.c.createProgressBar(pool, false, types.BlobInfo{Digest: reusedBlob.Digest, Size: 0}, "blob", "skipped: already exists")
d := reusedBlob.Digest
label := "skipped: already exists"
if d == "" {
d = srcInfo.Digest
label = "skipped: already exists (found by TOC)"
}
bar := ic.c.createProgressBar(pool, false, types.BlobInfo{Digest: d, Size: 0}, "blob", label)
defer bar.Abort(false)
bar.mark100PercentComplete()
}()
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12 changes: 7 additions & 5 deletions internal/private/private.go
Original file line number Diff line number Diff line change
Expand Up @@ -81,8 +81,9 @@ type ImageDestination interface {
// UploadedBlob is information about a blob written to a destination.
// It is the subset of types.BlobInfo fields the transport is responsible for setting; all fields must be provided.
type UploadedBlob struct {
Digest digest.Digest
Size int64
Digest digest.Digest
Size int64
TOCDigest digest.Digest
}

// PutBlobOptions are used in PutBlobWithOptions.
Expand Down Expand Up @@ -117,14 +118,15 @@ type TryReusingBlobOptions struct {
EmptyLayer bool // True if the blob is an "empty"/"throwaway" layer, and may not necessarily be physically represented.
LayerIndex *int // If the blob is a layer, a zero-based index of the layer within the image; nil otherwise.
SrcRef reference.Named // A reference to the source image that contains the input blob.
TOCDigest *digest.Digest // If specified, the blob can be looked up in the destination also by its TOC digest.
TOCDigest digest.Digest // If specified, the blob can be looked up in the destination also by its TOC digest.
}

// ReusedBlob is information about a blob reused in a destination.
// It is the subset of types.BlobInfo fields the transport is responsible for setting.
type ReusedBlob struct {
Digest digest.Digest // Must be provided
Size int64 // Must be provided
Digest digest.Digest // Must be provided, can be empty if TOCDigest is present
TOCDigest digest.Digest // Must be provided, can be empty if Digest is present
Size int64 // Must be provided
// The following compression fields should be set when the reuse substitutes
// a differently-compressed blob.
CompressionOperation types.LayerCompression // Compress/Decompress, matching the reused blob; PreserveOriginal if N/A
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